Research progress on Ti-based materials for MgH₂ hydrogen storage systems

Abstract

Magnesium hydride (MgH₂) as a solid-state hydrogen storage material has obtained intense attention in extensive research because of its high hydrogen-storage capacity, excellent reversibility, and relatively low cost. However, two primary obstacles of slow kinetics during hydrogenation/dehydrogenation process and high thermodynamic stability of Mg-H bond hinders the large-scale application of MgH₂. Therefore, developing high-efficiency catalysts is necessary for hydrogen storage systems. Titanium (Ti) as an active element, shows promising in enhancing hydrogen storage activity and has been reported extensively. Herein, this review summarized the synthesis approaches, testing technology, and hydrogen storage performance of various Ti-based additives in detail. The structure-activity relationship of Ti-based materials was researched by combining experiment and DFT simulations. In particular, the focus is on the investigation of synthesis, characterization and reaction mechanism of various Ti-based additives. The real active sites and different reaction mechanisms during MgH₂ hydrogen storage system are discussed. Finally, a summary and outlook were also presented. This review has the potential to guide the design of high-efficient catalysts and provide embedded guidance for future development and application of Mg-based materials in hydrogen storage system.

Graphical abstract

Keywords

Hydrogen storage / Ti-based additives / Structure-activity relationship / Magnesium hydride

1. Introduction

1.1 Necessary and significance of developing hydrogen storage material

The increase of anthropogenic carbon dioxide emissions, and consumption of fossil fuels boost the development of new energy to improve the global environment and achieve carbon neutrality [1-4]. Hydrogen has been considered as one of the most promising substitutes for fossil fuels because of its high-gravimetric energy density (142 MJ•kg^-1), non-toxicity and clean-burning characteristics [5-10]. However, hydrogen is a very low-density gas at room temperature and pressure, which results in a very low volumetric energy density [11-14]. Hydrogen storage technology is the core link in the hydrogen energy industry chain and is crucial to the realization of the “hydrogen energy economy”, which are technologies developed to overcome the inherent low-density defects of hydrogen [15-18]. Despite the continuous development of hydrogen storage technology, it still faces several key constraints that limit the large-scale application of hydrogen energy. Such as, low volumetric energy density, high cost and the others [19-21]. Numerous efforts have been exerted to explore appropriate strategy to store hydrogen, such as high-pressure, cryogenic and solid-state hydrogen storage systems [22-24]. Currently, methods for hydrogen storage consist of high-pressure gaseous state, low-temperature liquid state and solid material hydrogen storage. Compared to conventional hydrogen storage technologies, the hydrogen storage from solid materials occupies the dominant position because of their volume-based density, remarkable reliability and considerable energy efficiency [25-27]. Magnesium hydride (MgH₂) is a main representative of Mg-based hydrogen storage materials, which have small density, no pollution, low price, high hydrogen storage capacity [28-31]. However, high thermodynamic stability causes high de-hydrogenation temperature (above 420 ℃) in this system and leads to slow sluggish kinetics [32-34]. The design of efficient catalysts is critical to design active sites with highly active structures to facilitate dissociation and hydrogen release for MgH₂ hydrogen storage system [35-37]. Therefore, intensified endeavors are carried out to reduce the thermodynamic stability and kinetic barrier, aiming to meet the practical utilization in the portable and stationary industries, such as alloying [38-44], nanoparticle sizes [45-50], and catalysts doping [51-56]. The hydrogen absorption and desorption reaction pathways as well as the thermodynamic properties of MgH₂ can be effectively enhanced through the incorporation of these methods into the MgH₂ system [57-59]. As shown in Fig. 1, the past decades have witnessed a significant increase in both publications and citations, along with a diverse classification of these articles. Within this field, the development of rational strategies is crucial for enhancing the performance of MgH₂ hydrogen storage systems.

1.2 Overall research progress and basic content

Transition metal-based catalysts, for example, Ti, Ni, Co, Fe and the others as the metal sites significantly presented excellent performance in different fields [60-63]. Based on this, transition metal-based materials have promising in improving the reaction kinetic parameters of MgH₂. Illustratively, Ti-based catalysts convey higher catalytic behavior during de/re-hydrokinetic process [64-66]. Among these methods, the introduction of additives is an effective design strategy to enhance hydrogen storage performance of Mg-based composites [67,68]. Ti-based compounds, such as Ti-halides, Ti-hydrides, Ti-oxides and so on are widely used in the field of catalytic modification of MgH₂ hydrogen storage system [69-73]. Additionally, the confirmation of structure and determination of structure-activity relationship is important for the investigation of the reaction mechanisms [74-76]. Recently, a comprehensive review of solid-state hydrogen storage based on absorption was conducted involving synthesis methods, hydrogen storage properties, and recent advances [77-81]. Research on the electrochemical hydrogen anion (H^-) driven hydrogen storage mechanism was developed and designed material with anti-α-AgI crystal structure, which exhibits excellent hydrogen anion conductivity and electrochemical stability, which can achieve high-capacity reversible hydrogen storage at low temperatures [82]. Niobium oxide (NbO_x) nanoparticles are constructed to enhance the kinetic barriers of hydrogen storage in MgH₂, which conveyed excellent performance [83]. Therefore, the summary of recent advances and mechanism investigation of Ti-based additives on MgH₂ hydrogen storage performance is necessary to provide reference for developing the research in hydrogen storage field.

In this review, the advances insights into Ti-based materials for MgH₂ hydrogen storage on the aspects of design paradigms, activity evaluation and mechanism elucidation are systematically summarized. The detailed discussion consists of reaction mechanism, structure-activity relationship of Ti-based additives, universal synthetic approaches, testing techniques in hydrogen storage system. The existing problems that remain unsolved and potential solutions are put forward and deliberated upon. Finally, the final summary and future outlook of the Ti-based additives on MgH₂ hydrogen storage system was discussed in the aspects of the design of additives, the characterizations of Mg-based composites, the insights into structure-activity relationship, the construction of diversified hydrogen storage system and the development strategy of hydrogen storage technology in MgH₂ hydrogen storage system. The combination of study on experimental and computational results in Mg-based hydride can provide support for developing high-efficiency Ti-based materials for the hydrogen storage field (Fig. 2).

1.3 Features and significance of this review

Hydrogen energy as a carrier of clean energy has become increasingly prominent. Although MgH₂ has a theoretical hydrogen storage capacity of 7.6 wt.%, its high dehydrogenation temperature and slow reaction kinetics limit its practical application [84,85]. Remarkable research has been done in MgH₂ hydrogen storage to reduce dehydrogenation temperature, involving the design of high-efficiency additives, exploring hydrogen storage mechanisms, and the exploration of practical applications [86,87]. However, challenges still exist in current research. Therefore, it is necessary to present a comprehensive and in-depth review to convey the whole research in design strategy, hydrogen storage performance improvement and mechanism insights. The application of Ti-based additives significantly improves the hydrogen absorption/desorption performance of MgH₂-based material, which is significant for promoting efficient and safe hydrogen energy storage technology. The features and implications of this review are as follows.

(1). Investigation of action mechanisms of Ti-based additives: Revealing reaction pathways is significant for boosting hydrogen storage efficiency of MgH₂. Ti-based additives have the ability to significantly reduce dehydrogenation temperature and increase the performance of MgH₂ during hydrogen storage system. The analysis of reaction mechanism is significant for understanding reaction mechanism. It is vital to reveal the action mode of Ti-based additives affecting the chemical reaction kinetics on MgH₂ surface, including the decomposition of MgH₂ molecules, the diffusion of hydrogen atoms, and the microscopic processes of new phase formation. In this review, the action mechanism of MgH₂ on Ti-based materials is summarized, which is important for designing high-efficiency materials that enhance activity, stability, and boost the release of hydrogen. In this review, the action mechanism of MgH₂ on Ti-based materials is summarized and this is important for designing high-efficiency materials, enhancing activity and stability, and boosting the release of hydrogen.

(2). Exploration of structure-activity relationship: The investigation on structure-activity relationship of Ti-based materials based on MgH₂ can provide valuable evidence for hydrogen storage science. A close relationship between structural design and performance improvement exists in MgH₂ hydrogen storage system. Understanding the structural properties of Ti-based additives is vital for the development of hydrogen storage. After introducing Ti-based additives, the crystal structure of MgH₂ may change, leading to a decrease in nanosize and an increase in specific surface area. The in-depth discussion of structural changes in hydrogen storage performance is significant for the design of optimized hydrogen storage materials and provides theoretical guidance for researchers in hydrogen storage fields. This review can provide a scientific foundation for designing innovative materials, and promote development of the hydrogen storage field of MgH₂.

(3). Reflection on strategies for materials design: The key of design strategy lies in improving hydrogen storage performance and reducing the dehydrogenation temperature of hydrogen storage materials, which can provide a foundation for efficient and reliable hydrogen energy storage. This review presents some reflections on materials design and points out the importance of design strategies. The rational design of materials from the aspects of the optimization of catalytic active sites, regulation of structure, development of composite designs can greatly improve activity and provide scientific guidance and technical support for the development of materials with high-efficiency. It provides solid technical support and broad innovation space for future hydrogen energy storage, promoting the revolution of hydrogen energy technology.

In conclusion, this review plays a role as a bridge to connect basic scientific research and industrial application. This review has the following advantages: (1) building a comprehensive knowledge framework that allows researchers to have a clearer understanding of MgH₂ hydrogen storage system. (2) understanding the action mechanism of Ti-based materials in hydrogen storage system. (3) reflecting the latest achievements in this field and has the ability to stimulate more innovative thinking and realize the hydrogen economy society.

2. Advances in mechanism investigation

2.1 Technologies in analyzing mechanism

MgH₂ and its complex have attracted positive attention as a material because of their low cost, safety and resources abundance. Ti-based additives have consistently emerged as appealing candidates for enhancing the kinetics and modifying thermodynamics of various hydrides, thereby lowering their working temperatures [70,88]. Through XRD technology, the phase composites can be achieved by detecting the diffraction peak of the substances after reaction or not. And then according to the change of the diffraction peak of the substances, the active substances with optimistic effect can be obtained. This is helpful for confirming the real active substance during the process of hydrogenation and dehydrogenation. Additionally, combing XPS technology, the valence state of the materials surface can be investigated. Combing the above-mentioned results of XRD and XPS, a clear mechanism towards MgH₂ can be provided. The XRD and XPS technology are the common and basal method to support the analysis on the hydrogen storage mechanism [89-91]. Our group has been done many works to explain the reaction mechanism in virtue of the XRD, HRTEM and XPS technologies. And through these operations, the change of the phase structure can be obtained (Fig. 3). And the other technologies, such as in situ technologies also play an important role in analyzing the mechanism of hydrogen storage materials. XRD and HRTEM of MgH₂+5Na₂Ti₃O₇-O_v was operated to reveal possible relevant mechanism. The results indicate the existence of O_v vacancies. The above results confirm that the Na₂Ti₃O₇-O_v exists stably in MgH₂+5Na₂Ti₃O₇-O_v in different states [90]. Fig. 3a-3c is the fabricated K₂Ti₈O₁₇ nanobelts, the compositional and structural analyses based on XRD and HRTEM demonstrate the stable oxygen vacancies in the K₂Ti₈O₁₇ and responsible for enhancing kinetics of MgH₂ dehydrogenation [91]. Additionally, XRD and HRTEM are used to confirm the reaction mechanism of Ti₃C₂-supported praseodymium(III) fluoride (PrF₃) NPs (PrF₃/Ti₃C₂) composite. The electron transfer among Ti-species of Ti⁰, Ti²⁺, and Ti³⁺ is the key to enhance hydrogen storage properties of MgH₂ [92]. Through XRD technology, the changes in phase transformation and chemical valence state of MgH₂/TiO₂ at different states can be explored. In the as-synthesized MgH₂/TiO₂, MgO is not detected. After dehydrogenation, the peak positions of Mg and MgO were observed. In the subsequent process of hydrogen absorption, Mg phase transforms to MgH₂ and Mg₂TiO₄. The Mg-Ti oxide phase possess a positive effect for MgH₂ de/re-hydrogenation. Furthermore, ¹H NMR test was used to confirm the catalytic substance. Additionally, in situ HRTEM and ex-situ XPS are used to present reaction mechanism of MgH₂/TiO₂. The results confirm that multi-valance of Ti species are responsible for the high stability and kinetically accelerated hydrogen sorption performances [93] (Fig. 3d-3f). XPS investigation was operated to demonstrate the effect of TiF₄ during the decomposition of MgH₂. The XPS results confirm that the change in the chemical state of titanium from Ti⁴⁺ to Ti³⁺/Ti²⁺ states and acts as an active site to enhance the dissociation of hydrogen atoms [94]. Based on this, the characterizations technologies are used to testify the existence of active substances or not and to provide for the design of high-efficiency materials to enhance the hydrogen storage performance. Furthermore, DFT calculation is also a technology to convey the reaction mechanism during the hydrogen storage system and a detailed information was presented in this review.

2.2 Reaction mechanism

2.2.1 Multiple valence titanium mechanism

Multiple valence titanium mechanism refers to the generated multiple valence of titanium during the process of hydrogen absorption and release. The generated Ti-based species during the reaction process is the active substances in improving the hydrogen storage performance of Mg-based composites. The generated multiple valence titanium can be analyzed by XRD, HRTEM, XPS and the other in-situ or ex situ methods. The key process in this mechanism is redox reaction following an electron transfer. Ni/TiO₂ was introduced into MgH₂ to improve the hydrogen storage properties. Combing the XRD, XPS, HRTEM technology, Ni reacts with Mg to form Mg₂Ni particles after dehydrogenation, and then transform into Mg₂NiH₄ in the subsequent process of re-hydrogenation. During the process of hydrogen storage system, the contents of Ti⁴⁺ generated in ball-milled process is higher than that in the process of dehydrogenation, and the Ti^3+/2+ has a relatively lower content. The results illustrate that higher valence of TiO₂ was changed into lower Ti^3+/2+ during the process of dehydrogenation. The multiple valence of Ti compounds has the ability to provide electron transmission channels on Mg/MgH₂. The multiple valence of Ti^4+/3+/2+ in the system can achieve e^- from H^- and give e^- to Mg²⁺, thus boosting the generation of H₂ and Mg. The enhanced hydrogen storage properties of MgH₂-Ni/TiO₂ was assigned to the synergistic catalytic effect of Mg₂Ni/Mg₂NiH₄ and the multiple valence of Ti^4+/3+/2+ compounds [95] (Fig. 4a). TiO₂@C was prepared and showed efficient performance on MgH₂. During the analysis of the materials, TiO₂ in the material reduces to lower valence during hydrogen storage process. The multiple valence of Ti leads to the weaker bonding of Mg‒H, improving the dissociation of hydrogen decreasing activation energy of MgH₂ [96] (Fig. 4b). Self-assembly of TiO₂ NPs on Ti₃C₂T_x are synthesized and present excellent hydrogen storage performance MgH₂ system. M-TiO₂/Ti₃C₂T_x was generated after introducing into MgH₂ system. The interfaces can act as hydrogen diffusion channels to improve the electron transfer and thus promote the performance. Multiple valence Ti of Ti⁴⁺, Ti³⁺, Ti²⁺, Ti⁰ promote the interaction between MgH₂ and Mg, H₂ and thus improve the hydrogen storage kinetics [97] (Fig. 4c-4e). Ni/Ti₃C₂ is fabricated and shows optimal catalytic activity. The electron transfers in multiple valence Ti of Ti⁰, Ti²⁺, Ti³⁺, Ti⁴⁺ are responsible for the enhancement of catalytic performance [98] (Fig. 4f). TMTiO₃ (TM = Ni and Co) were prepared and present excellent hydrogen storage performance in MgH₂ system. Ni element transforms into Mg₂NiH₄ and Mg₂Ni, and Ti element exist with a series of valences of Ti²⁺, Ti³⁺, and Ti⁴⁺. The synergistic interaction of Mg₂Ni/Mg₂NiH₄ with multivalent Ti leads to advantageous high-efficiency hydrogen desorption characteristics in the MgH₂ system [99] (Fig. 4g). A MgH₂/TiO₂ heterostructure with enhanced hydrogen storage performances was designed and the synergistic effects of multi-valance of Ti species accelerated electron transportation accelerated hydrogen storage performances of the composite [93] (Fig. 4h). Additionally, the other metal-based material also conveys the multiple valence metal mechanism. NbN NPs with intrinsic multiple valence of Nb⁵⁺-N/Nb³⁺-N were prepared and used in MgH₂ system. NbN NPs presented superior catalytic effect on de/re-hydrogenation kinetics for MgH₂/Mg system. The existence of Nb³⁺-N and Nb⁵⁺-N as the medium and play an important role for electron transfer and thus has the promising in enhancing the catalytic kinetics in system (Fig. 4i) [100].

In conclusion, the multiple valence Ti mechanism referred to Ti element undergoes valence state changes during reaction (such as the conversion of Ti³⁺ and Ti⁴⁺), which can act as a "reaction center" can promote the dissociation of hydrogen molecules and the transport of hydrogen atom. The valence change of Ti element allows it to capture electrons from hydrogen molecules to dissociate them into H⁺. The Ti element in this mechanism has a definite, variable valence state. When the initial form of the material is a compound of Ti (rather than elemental Ti), experimental characterization has the ability to observe the presence of Ti in different valence states and its changes during the reaction.

2.2.2 “Hydrogen pump” effect mechanism

“Hydrogen pump” mechanism is an effect between the generated active substances and MgH₂ system. Many studies have found that Ti usually forms TiH₂ or TiH_x with hydrogen during the reaction. These hydrides are very stable and difficult to reversibly dehydrogenate. However, the presence of TiH₂ or TiH_x greatly accelerates the process of hydrogen absorption and release of Mg. This differs from the reversible changes in Ti valence states in the “multiple valence Ti mechanism” and therefore requires new theories to explain it. “Hydrogen pump” mechanism can regard Ti-based catalyst particles as a miniature “pumping station” can efficiently completes the “inhalation” and “discharge” reaction of hydrogen at the phase interface of the materials. This mechanism is particularly useful for interpreting the system of Ti or TiH_x. It highlights the physical role of materials as hydrogen atom diffusion channels and interfacial reaction platforms. For example, characterizations through XRD and TEM reveal a recognized reciprocal phase shift between Mg₂Ni and Mg₂NiH₄. The generated Mg₂Ni and Mg₂NiH₄ were called “hydrogen pump” effect. The “hydrogen pump” effect makes the rapid hydrogen release of MgH₂/Mg. Additionally, Ti-based MXene turn into Ti⁰ during the process of ball milling, dehydrogenation and re-hydrogenation. Integrating both experimental and theoretical evaluations, the synergistic effect of Ti⁰ on Mg₂Ni/Mg₂NiH₄ is responsible for the perfect reaction kinetics and reaction stability of MgH₂. The synergistic effect of Ti on the Mg₂Ni/Mg₂NiH₄ “hydrogen pump” could provide approaches to improve the hydrogen storage properties of MgH₂ [101] (Fig. 5a, 5b). Moreover, “hydrogen pump” existed in Mg@Pt, and the results demonstrated that Pt on Mg particles conveyed a “spillover” effect to ameliorate hydrogen absorption kinetics [102]. DFT calculation and in situ TEM confirmed that H-stabilized Mg₃Pt can be considered as a “hydrogen pump” for MgH₂ dehydrogenation and then changed into Pt after the operation of desorption. Mg₃Pt can change into Pt with the release of H atoms. Therefore, Mg₃Pt can act as a “hydrogen pump” to transfer H atoms and facilitating the hydrogen release performance (Fig. 5c-5e).

The “hydrogen pump” mechanism has similar significance in improving hydrogen storage performance. This all refers to the fact that the generated active substances play a crucial role in the generation of active substances during the process of MgH₂ system. This can provide useful guidance in analyzing the reaction mechanism during hydrogen storage system.

2.2.3 Electron transfer effect mechanism

The study of detailed mechanism of electron transfer effect was conducted. These materials just like “electron catalyst” to improve the electronic environment. Electron transfer effect mechanism is explained at the electronic level rather than the atomic transport level. The addition of Ti adjusts the electronic structure of the Mg-based materials, changes the fermi level or density of Mg/MgH₂, weakens the strength of Mg-H bonds, makes it easier for hydrogen atoms to break from the lattice of MgH₂ and thus reduces the energy barrier of hydrogen desorption [103]. The creation of dispersed Co metal nanoparticles on TiO₂ (Co/TiO₂) showed an enhanced catalytic impact on the hydrogen de/absorption characteristics of MgH₂. The impact of electron transfer is vital in improving the efficiency of hydrogen storage. Electrons in TiO₂ valence band (VB) are stimulated by the conduction band (CB), leading to their migration to Co surfaces due to TiO₂ elevated Fermi level compared to Co. Consequently, the Co surfaces are abundant in electrons, resulting in holes remaining on TiO₂. Due to its d-band electron configuration, the material exhibits a stronger bond with H (Co-H) compared to Mg-H, thereby easing the process of storing hydrogen. Furthermore, the presence of electrons surrounding Co simplifies the transition of Mg²⁺ into Mg. The presence of H^- at the junctures of Mg/MgH₂ and Co/TiO₂ creates openings near TiO₂, resulting in the creation of H₂. Electrons surrounding Co will shift e^- to H atoms, leading to the subsequent process:

(2.2.3.1) $H + e^{-} → H^{-}$

(2.2.3.2) $Mg + 2h^{-1}→Mg^{2+}$

In terms of Mg, it will get the holes from the TiO₂ and Mg²⁺ is formed. Thus, Co/TiO₂ composite acts as “nano redox reactor” can greatly promote the dissociation and release of hydrogen, thus boosting the reaction kinetics of MgH₂. Additionally, the increase of charge carriers will have the ability to enhance redox reaction of catalysts, and further promote the catalytic kinetics of hydrogen de/absorption [104]. Additionally, DFT show that the introduction of Ti can significantly reduce the enthalpy change of dehydrogenation reaction, and provide evidence from the perspectives of electron local function (ELF) and charge density distribution [105].

In conclusion, for the whole reaction process, the mechanism containing the generation of multiple valence titanium, and the “hydrogen pump” effect maybe exist during the dehydrogenation and hydrogen absorption reactions. The comparison of different reaction mechanisms was listed in Table 1. And from the above-mentioned results, the existence of multiple valence Ti has the promise in boosting the electron transfer.

2.2.4 In-depth analysis of different mechanisms

The common goal of above-mentioned mechanism is to reduce the kinetic energy barrier of hydrogen absorption and release reaction of Mg-based hydrogen and thus facilitating the kinetics of hydrogen storage. Therefore, for the prepared materials, the investigation on the hydrogen storage mechanism still has many works to do. And the experimental and theoretical operations can be combined to understand the reaction mechanism in depth and explain their structure-activity relationship system. These mechanisms can occur simultaneously and synergistically. The “multiple valence titanium mechanism” and the “electron transfer effect mechanism” all involve the redistribution of electrons. However, the difference of these mechanisms is as follows, “multiple valence titanium mechanism” and the “electron transfer effect mechanism” focus on the explanation at the electronic level, while the “hydrogen pump” effect focuses more on physical images of atomic transport and interfacial processes. Additionally, the catalyst states are different, they correspond to different forms of catalysts (compounds, hydrides, doped atoms) and are therefore suitable for different experimental observations.

The classification of mechanisms stems from different explanatory models proposed by researchers for the same catalytic phenomenon based on different experimental phenomena and characterization techniques. When the materials precursor is Ti-based compound, researchers can observe valence changes of Ti through XPS and other methods, which are explained by the multiple valence titanium mechanism. When stable TiH₂ formation and generate interface with Mg phase was observed. Although TiH₂ appears to be “inactivated”, its performance is improved, giving rise to the “hydrogen pump” effect mechanism. This model can support by HRTEM and phase interface evolution. When Ti is highly dispersed in atomic form, the reaction mechanism is difficult to explain by interface or particle effects, theoretical calculations show changes in electronic structure, thus suggesting an electron transfer effect mechanism.

In summary, these three mechanisms reflect three different roles that Ti-based materials play in Mg-based hydrogen storage: redox mediators, hydrogen atom high-speed channels, and electronic structure regulation. Which mechanism is dominant depends on the chemical environment, size, distribution of the materials, and their interaction with the Mg-based matrix. In the actual reaction, these mechanisms conveyed coordination effect to enhance the hydrogen storage performance of Mg-based materials. It is necessary to comprehensively use advanced in situ characterization technologies and theoretical calculations to thoroughly clarify the reaction mechanism.

2.3 Theoretical research of Ti-based additives on hydrogen storage

2.3.1 Purified DFT calculation

The investigated on DFT calculation, such as, adsorption energy, charge transfer and electronic density of states is significant for the MgH₂-based hydrogen storage system [106]. Ti-based materials have been done many researches on the pure DFT calculation. DFT investigation of Mg₇XH₁₆ (X=Ti, Zn, Pd, and Cd) was conducted for hydrogen storage applications. The calculated systems presented lower formation enthalpy and improved hydrogen releasing capacity [107]. DFT was used to reveal the effect TiO₂/C/Ni and MgH₂. Results confirm that the strong electronic interaction between TiO₂/C/Ni and MgH₂ weakened the Mg-H bond energy and elongated the Mg-H bond, thus boosting hydrogen storage performance [108]. The role of Ti, Nb, Al, and In in the diffusion of hydrogen atoms into Mg-based was studied by DFT calculations. Ti, Nb, and Al have been promising in substituting Mg in inner layers. The existence of the subsurface Ti or Nb atoms can enhance hydrogen atom diffusion. However, the doped Al or In atoms can provide support for the formation of MgH₂ [109] (Fig. 6a-6d). DFT calculation was applied to investigate the surface stability of TiMn₂ film and the hydrogen storage performance of Mg/TiMn₂ interface. The interface between Mg and TiMn₂ film is greatly facilitated the hydrogenation performance of Mg [110]. 2D Ti₂C MXene as an additive was used to boost the dehydrogenation of MgH₂. And the MgH₂ molecule adsorption on 2D Ti₂C and Ti₂CT₂ were also studied. The results confirm that TiH₂ was produced in Ti₂C/MgH₂ interface during dehydrogenation process. The electron transfer into carrier and in situ formed TiH₂, which has the ability to expedite the hydrogen storage performance of MgH₂. Additionally, radial distribution functions (RDFs) are used to research the bond changes of Mg-H and Ti-H in Ti₂C/MgH₂ and Ti₂CT₂/MgH₂ interface during the process of dehydrogenation. The results confirm that more H₂ molecules was generated in the interface of Ti₂C(OH)₂/MgH₂ [111] (Fig. 6e-6i). The structure, elastic modulus, Debye temperature, and heat capacity of four TiH₂ were analyzed using DFT calculations. Findings verify the stability of tetragonal TiH₂ compared to cubic TiH₂. Cubic and tetragonal TiH₂ exhibit a Debye temperature exceeding that of orthorhombic TiH₂ [112] (Fig. 6j-6k). Additionally, investigations were operated on hydrogen storage system of MgH₂ by Ti and Fe co-doping and the results confirmed that their addition presented excellent performance[113-116].

2.3.2 Experimental verification guided by DFT calculation

The investigation on the experimental and theoretical studies plays a vital role in improving the dehydrogenation thermodynamics of MgH₂ doped with additives. The experimental verification based on the results of DFT calculation is necessary for the researchers to study the hydrogen storage of MgH₂ composites. Some works have been done in aspects of experimental and DFT. Combined with DFT calculations and experimental study, the thermodynamic effects of doped Ti and Ni on MgH₂ reaction were studied [117] (Fig. 7). The results demonstrated that the introduction of Ti or Ni can decrease the reaction enthalpy and initial dehydrogenation temperature of MgH₂. The local lattice distortion of MgH₂ induced by dopants is responsible for the enhanced dehydrogenation thermodynamics. The electron structure analysis showed that the thermodynamics of dehydrogenation of doped MgH₂ is closely related to bonding characteristics of M-H(where M = Mg, Ti, Ni) in the energy gap and lattice near Fermi level. Smaller energy gap and more pronounced covalent bonding characteristics suggest that the thermodynamics of dehydrogenation of MgH₂ is more favorable. For instance, in the low-temperature region, the dehydrogenation onset and peak temperatures of the three ball-milled samples follow a decreasing order: MgH₂, MgH₂-Ti, and MgH₂-Ni. Based on DFT calculation, the internal mechanism of in situ hydrolysis in a representative Ti-based MXene (Ti_xC) system is studied and the results confirm that Ti_xC undergoes hydrogen-driven structural restructuring, which boost the performance [118]. This experimental observation is in excellent agreement with the theoretical calculations of the enthalpy change (ΔH) and energy difference (ΔE).

In conclusion, theoretical research on Ti-based additives in hydrogen storage shows that for most Ti-based catalyst systems, especially those containing nanoscale Ti particles or hydrides, the excellent catalytic performance mainly comes from the “hydrogen pump” effect. DFT can provide solid quantitative evidence. Additionally, DFT calculations can support the existence of electron transfer effects, which can quantitatively or semi-quantitatively indicate that the strength of Mg-H bonds is weakened in the presence of Ti. And at the atomic scale, the reaction energy barrier is weak, which complements the “hydrogen pump” effect rather than repelling each other. For the multiple valence titanium mechanism, DFT calculations can confirm that the real catalytic active sites may be the generated interface after the reaction. Thus, in the field of application design of Mg-based hydrogen storage materials, the combination of experiment and theory is important for promoting the development of this field. Through experiments, the performance of Mg-based hydrogen storage materials under different conditions can be intuitively observed, such as hydrogen storage capacity, hydrogen absorption and release kinetics, cycle stability, etc. Theoretical research has the ability to provide direction and guidance for experiments. Using theoretical methods such as quantum mechanics and molecular dynamics, can gain an in-depth understanding of the structure and interactions of Mg-based hydrogen storage materials, and predict the properties and behaviors of materials. Theoretical calculations can provide guidance to understand the thermodynamic and kinetic mechanisms of hydrogen storage and explain the phenomena observed in experiments. The combination of experiment and theory can accelerate the research and development process of Mg-based hydrogen storage materials. In the practical application design, theoretical prediction can screen out material systems with potential excellent properties, and then verify and optimize them through experiments. If the experimental results do not match the theoretical predictions, the theoretical model can be further modified to more accurately describe the properties of the material. This cyclic and iterative process can greatly improve research efficiency and reduce the corresponding costs.

3. Design strategies of MgH₂-based additives

3.1 Reactive ball-milling

Ball-milling is an effective strategy to reduce crystallite sizes and introduce more active sites, which have an important role in hydrogen dissociation [119-122]. Reactive ball milling (RBM) was operated during exothermic reactions between the gas- and metallic solid phases at almost room temperature and was considered as a powerful method to fabricate different materials [123-126]. RBM has been used to prepare metal hydrides, such as, MgH₂ and their composite. The operation of ball-milling metal hydride materials has the ability to help generate fresh metal surfaces, increases surface area, forms defects and so on [127-129]. Synthesis by RBM under hydrogen atmosphere is a potential method to prepare hydrogen storage materials [130,131]. Mechanical ball-milling as a simple and efficient way has been used in the preparation of the Mg-based hybrids and play important role in energy storage. MgH₂ and the synthesized catalysts with different forms and compositions can mix uniformly to generate nano-structured Mg-based composites. Illustratively, the defect was introduced into the composites during the process of ball-milling. And the introduction of defect and decrease of the NPs has the promising in providing abundant active substances for the hydrogen storage performance and decreasing hydrogen diffusion pathway, thus improving the catalytic kinetic performance of reaction activity of hydrogen storage materials [39,132,133]. A wet chemical ball milling strategy was used to design Mg-NiTiO₃ and used in hydrogen storage properties of Mg [134]. TiFe was synthesized and doped into MgH₂ to enehance the de/re-hydrogenation performance of MgH₂. Compared with MgH₂, the onset desorption temperature has a decrease after adding TiFe into MgH₂, which present excellent performance for MgH₂ hydrogen storage [135]. NbN NPs were milled with MgH₂ and present excellent hydrogen storage performance of MgH₂ [100]. Mechanical grinding was used to obtain Mg-based alloys La7Sm3Mg80Ni10+5 wt.% M (M = None, TiO₂, La₂O₃). The addition of catalysts reduces the time of releasing hydrogen and the hydrogen desorption activation energy [136]. 2D vanadium nanosheets (V_NS) were synthesized through wet chemical ball milling strategy and have high effective in boosting hydrogen storage performance of MgH₂. The optimal material began to release hydrogen at 187.2 °C, and this temperature is inferior than that of MgH₂ [137] (Fig. 8a-8c). PdNi bilayer metallenes are designed and used for hydrogen storage of MgH₂. The d-band center of PdNi cluster is closer to the Fermi energy level than other hydrogen absorption system, making the adsorption of H-atoms easier (Fig. 8d). Through the corresponding experimental and theoretical simulations, active substance with in situ formation of PdNi alloy clusters, including Pd/Ni phase clusters and Pd/Ni single atoms, with appropriate d band centre, obtained by using metallene ball milling to enhance hydrogen storage capacity of MgH₂ [138]. Few-layer MXene Ti₃C₂T_x supported Ni@C (Ni@C/FL-Ti₃C₂T_x) was served as an efficient catalyst for hydrogen desorption of MgH₂. MgH₂+10 wt% Ni@C/FL-Ti₃C₂T_x composite conveys superior kinetics and excellent cycling stability [139]. The transition metal phosphides are also used in preparing the corresponding catalysts. Namely, Ni₂P as an additive was append to MgH₂ through ball-milling strategy. The activation energy of desorption of Ni₂P-doped MgH₂ composite is lower than pure MgH₂. MgH₂-Ni₂P transforms into Mg₃P₂ and Mg₂NiH₄ and thus instantly lower the hydrogen desorption temperature of MgH₂ [140] (Fig. 8e).

Summarily, different planetary mill of stainless steel vials with volume and balls with diameter at a certain rotational speed for some times during the process of ball milling maybe has different effect on the hydrogen storage of Mg-based materials. The weight ratio of sample to ball, the time of ball-milling and the other milling parameters may have different effect on hydrogen storage properties. Through different contrastive experiments, the optimal parameters can be achieved and provide theoretical guidance for developing the hydrogen storage system.

3.2 Plasma-assisted milling

Plasma-assisted milling (P-milling) technology was developed by Professor Min Zhu group at South China University of Technology. P-milling refers to introducing cold field discharge plasma into mechanical vibration ball milling. The high-energy non-equilibrium plasma and mechanical ball mill are formed by using near-normal pressure gas in the ball mill tank [141,142]. Based on P-milling, a vibratory mill is established and dielectric barrier discharge plasma (DBDP) was introduced into the milling process, DBDP is a simple technique to create non-equilibrium plasma conditions at low gas temperatures and atmospheric-pressures. The introduction of DBDP can generate extra thermal explosion and high-energy electrons to powder during the process of ball milling and consider as an efficient method of powder crushing and alloying. The synergistic effect promotes the microstructure refinement, alloying, active activation, chemical reaction and accelerates the in-situ gas-solid phase reaction of the powder. These can greatly enhance the efficiency of ball milling, significantly decrease the pollution of ball mill, and form a unique structure to dramatically boost hydrogen storage performance [143] (Fig. 9a). Among those reversible hydrogen storage materials, Mg is a promising candidate because of its advantages of high hydrogen capacity, abundant resources, and low cost. However, the hydrogenation and dehydrogenation of MgH₂ usually requires high temperatures because of its high thermodynamic stability and kinetic barrier. The kinetic properties of solid solutes are still sluggish, thus long ball milling is required. Based on this, during the process of hydrogen storage of MgH₂, P-milling has the ability to implement the rapid formation of Mg-based solid solution and in situ induced Mg-based catalysts, thereby achieving the dual adjustment of thermodynamic and kinetic properties. Prof. Zhu group use P-milling technology has been done many research on the hydrogen storage of MgH₂. For example, P-milling was used to design Mg-In for the first time and the results confirm that P-milling has the ability to promote the generation of Mg₉₅In₅, and following the in situ generation of MgF₂ because of the reaction between Mg and polytetrafluoroethylene. The Mg(In)-MgF₂ composite has a much lower ΔH than that of pure MgH₂ [144]. Ultrafine WC-10Co hard metals with VC/V₂O₅ addition was prepared by assisted milling, reducing the particle size of W, Co and VC and improving mechanical properties of cemented carbide [145]. Mg₈₅In₅Al₅Ti₅ alloy was synthesized by P-milling and the dual-tuning effects of In, Al, and Ti boosts the corresponding thermodynamics and kinetics performance (Fig. 9b) [146]. Additionally, Al₂O₃, TiO₂ and Fe₂O₃ are introduced into Mg powders and the passivated Mg-TiO₂ composite presents optimistic hydrogen absorption properties of Mg and MgH₂ [147]. TiO₂ formed on the surface of Mg particles and the defects in Mg lattice boost hydrogen absorption properties.

In conclusion, for Mg-based hydrogen storage materials, P-milling has the ability to realize rapid generation of Mg-based solid solution, thereby realizing dual adjustment of thermodynamic and kinetic properties. P-milling provides a simple, economical, and pollution-free method for designing nano-materials or boosting mechano-chemical reactions, paving a way for future large-scale production of energy storage materials. Additionally, in addition to energy storage materials, the P-milling technology can also be used for the mass production of nano-sized metal and alloy powders, especially those that are difficult to synthesize by traditional ball milling technology.

3.3 Ultrasound-dri4.2.1.4 ven liquid-solid phase metathesis

Despite the attention MgH₂ has received, its volume is stable and hydrogen can only be released at impractically high temperatures. On this basis, Liu proposed a new ultrasonic driven liquid-solid phase process by taking advantage of the difference of solubility of metal hydrides and chloride in thermocouple. Through this method, MgCl₂ was dissolved in THF with mechanical stirring. Subsequently, LiH was added into THF solution and mixed using a magnetic stirrer. The obtained suspension was exposed to ultrasonic. Finally, ultrafine MgH₂ NPs (4-5 nm) were successfully harvested without supports (Fig. 10a). Unprecedented hydrogen storage capacity achieved due to the thermodynamic destabilization and reduced power barriers (Fig. 10b). The synthesized NPs present rapid hydrogen cycling behavior compared with bulk MgH₂ (Fig. 10c). Based on this, DFT calculation is conducted on the aspect of hydrogen molecular adsorption, desorption, and diffusion processes in MgH₂ nanoclusters and block models (Fig. 10d) [148]. The ultrasound-driven liquid-solid phase metathesis strategy has the ability to synthesize a wide range of nanomaterials, which include complex metal hydrides with higher contents of intrinsic hydrogen.

3.4 Single atom incorporating

Single atom-based catalysts (SACs) are currently widely used in the fields of CO₂ electroreduction [149], hydrogen generation [150,151] organic electrocatalytic synthesis [152,153], formic acid oxidation reaction [154], oxygen reduction reaction [155], biocatalysis [156] photocatalytic synthesis [157], and other fields [158]. The problem with hydrogen storage materials such as MgH₂ is that the temperature of hydrogen absorption and release is high and the kinetic performance is poor. Thus, a catalyst is needed to reduce the reaction energy barrier. SACs can provide more active sites and have promising in promoting the adsorption and dissociation of hydrogen and enhancing hydrogen storage because of their high atom utilization and unique electronic structure [159,160]. For example, Pd single atoms on Sc₂O₃ NPs and the Mg-Pd alloy generated during the hydrogen absorption and desorption process have an efficient hydrogen pumping effect, thus boosting the kinetic properties of MgH₂ [161]. Although SACs possess the advantages of higher efficiency and lower usage, possible challenges include stability, the tendency to aggregate, and inactivation during cycling of SACs existed in this field [162,163]. Therefore, the excavation of suitable catalysts based on SACs is necessary for the development of MgH₂ hydrogen storage systems. Transition metal-based SACs, such as Ni [164,165], Fe [166,166], or the combinations with noble metal-based SACs like Ru [167,168], Pd [169], Rh [170]. Illustratively, the selection of carrier materials, such as, carbon [171,172], carbon nitride [173], graphene [174] has the ability to stabilize single atoms and prevent their aggregation. The design on the structures of catalysts such as, doping [175], coordination structure regulation [176,177], MgH₂/single-atom heterojunctions [178], theoretical calculations were carried out to screen highly reactive metal single atoms, optimize their electronic interaction with the carrier, and enhance the hydrogen adsorption energy [179,180], defect engineering to stabilize single atoms and manipulate electronic structures [181,182], and so on. Additionally, developing low-temperature atomic layer deposition [183], pulsed electroreduction [184] and the others technology to realize the high loading and uniform distribution of single atoms. The above-mentioned modified strategies can increase the exposure of active sites and boost the reaction performance.

In summary, SACs can effectively catalyze the decomposition of MgH₂ and the release of hydrogen through the isolated active sites of metal atoms, reducing the reaction energy barrier. The high atomic utilization rate and unique electronic structure of SACs can enhance the adsorption/desorption capacity of hydrogen and accelerate the phase transition process of Mg/MgH₂. The atomic-scale dispersion of SACs avoids the agglomeration problems of conventional nanoparticle catalysts, thus maintaining catalytic activity over long cycles [185,186]. The combination of SACs with nanoparticles or two-dimensional materials to construct multi-level catalytic interfaces [187,188]. The application of SACs in the field of hydrogen storage is still in its infancy, and challenges such as large-scale preparation, high-temperature stability, and cost control need to be addressed [189]. Through multidisciplinary integration of materials science, chemical engineering, and artificial intelligence, it is expected that the practical application of SACs in on-board hydrogen storage systems or distributed energy resources will be realized in the future, promoting the commercialization of the hydrogen economy.

3.5 Other design strategies

Microwave assisted method was conducted under the generation of heat energy in the reactant molecules through microwave radiation energy, thereby facilitating the reaction. Due to the instantaneous, homogeneous and efficient nature of microwave radiation, the reaction speed can be greatly improved, and reduced the reaction temperature. Microwave radiation was used to enhance hydrogen storage of MgH₂. TiO_2-x generated through ball milling has the ability to absorb microwave radiation and act as “hot spots” (Fig. 11a, 11b) [190]. The production of Mg-Ti-H films was achieved through a one-step method employing microwave reactive plasma-assisted co-sputtering, and the composition of Ti playing a crucial role in the creation of these films [191]. The bottom-up approach for self-assembly was utilized in the creation of MgH₂ nanoparticles fixed to the 3D Ti₃C₂T_x surface. Enhanced hydrogen storage capabilities were achieved through the nanoconfinement and the multiphasic connections between MgH₂ (Mg), Ti-MX, and in situ formed TiH₂ (Fig. 11c) [40]. Additionally, MgH₂/TiO₂ heterostructure was synthesized following the bottom-up self-assembly of MgH₂ NPs anchored on TiO₂ NS. The MgH₂/TiO₂ heterostructure conveyed rapid reaction kinetics, low temperature, and stability (Fig. 11d) [93]. An innovative 1D N-doped, hierarchically porous carbon nanofiber (pCNF), derived from MOF, has been developed and utilized in the synthesis of MgH₂/Ni nanoparticles. The MgH₂/Ni@pCNF variant exhibited quicker desorption rates and a reduced initial desorption temperature in contrast to the standard MgH₂ (Fig. 11e, 11f) [192]. Additionally, Furthermore, Mg-Ti specimens, varying in Ti levels, were created by compressing nanoparticles cultivated through Inert Gas Condensation using separate Mg and Ti vapor sources [193].

Summarily, reactive ball-milling method is a common strategy for the hydrogen storage materials and presented excellent performance in enhancing the hydrogen release performance. Considering the development of the field of hydrogen storage, it is necessary to research other methods with high-efficiency, such as plasma-assisted milling, ultrasound-assisted milling, microwave assisted and so on, which are of great help for further enhancing the hydrogen storage performances of MgH₂. Table 2 was the comparison of different reaction strategies. From the results of Table 2, we can obtain that the advantages and disadvantages of each method are different, and the scope of application is also different. The choice of method was based on a combination of research objectives, available resources, and cost-effectiveness.

4. Universal research procedures in hydrogen storage system

4.1 Properties of hydrogen adsorption and desorption

Generally, the hydrogen absorption and desorption properties were evaluated by Sieverts' apparatus. Different groups have different method and the following are the measure method of our group [89-91]. And this maybe has some similar in testing the hydrogen absorption and desorption properties and can provide the guidance for the experiments of hydrogen storage. Typically, a certain quality of composites was sealed into a stainless steel tube in a glovebox. During the temperature-programmed desorption (TPD) test, the temperature was elevated from room temperature to the targeted temperature at a speed. From the TPD test, the initial dehydrogenation temperature can be obtained and then can judge the performance through TPD curves. For the isothermal experiments, the temperature was rapidly elevated to a specified temperature and maintained during the following test. After dehydrogenation, the sample was completely hydrogenated at certain temperature and press. From the above-mentioned results, the temperature of hydrogen release can be obtained [194-196]. This is a common method to judge the performance of composites in the hydrogen storage of Mg-based materials.

4.2 Evaluation of reaction kinetics and thermodynamics

4.2.1 Johanson-Mehl-AvramiKolmogorov model

The activation energy for the dehydrogenation process of composites was obtained by fitting the isothermal dehydriding curves at different temperatures using the Johanson-Mehl-AvramiKolmogorov (JMAK) equation. The JMAK equation is based on nucleation and growth events, and widely used to describe time-dependent kinetic behavior in isothermal solid-state reactions. The detailed information can be arranged as the following two format [39,142,144,197-199],

(4.2.1.1) \left[-\ln (1-\alpha \right)]{}^{1/\eta }=kt

(4.2.1.2) \ln [-\ln (1-\alpha )]=\eta \ln t+\eta \ln k

Herein, α is the reaction fraction, k is the rate constant, and η is the Avrami exponent. The hydrogen desorption fraction ranging from 0.2-0.5 was adopted to fit the kinetic curves. The Avrami exponent η was in the range 1.10 to 2.41, implying that the dehydrogenation reaction for the sample followed a diffusion-controlled mechanism. ln[-ln(1-α)] varies linearly with lnt, with a correlation coefficient of R²> 0.995, indicating that the JMAK equation is suitable for describing the dehydrogenation process [200-202].

The values of k were applied to calculate the dehydrogenation activation energy according to the Arrhenius equation [203-208],

(4.2.1.3) k=A{e}^{-\frac{E_a}{\text{Rt}}}

(4.2.1.4) \ln k=-\frac{E_a}{RT}+\ln A

Where, k is the rate constant, A is the pre-exponential factor, and E_a is the activation energy. Thus, the activation energy can be obtained by fitting lnk verses 1/T.

4.2.2 Kissinger’s method

Kissinger’s method is also usually used to calculate the dehydrogenation activation energy of hydride, typically using DSC experiments, following Kissinger’s equation [90,91,209-211],

(4.2.2.1) \ln \left(\frac{\beta }{T_p^2}\right)=-\frac{E_a}{R{T}_p}+C

In this formula, β is the heating rate; T_p is the peak temperature; R is the gas constant (R = 8.314 J mol⁻¹·K⁻¹); C is a constant. By fitting the linear relationship between β/T_p² and 1000/T_p, the activation energy (E_a) can be obtained using DSC results at different heating rates. Kissinger’s method has advantages of being simple and requiring few tests. However, only a single rate-limiting step is assumed, the application of the equation is limited [212-214].

4.2.3 Reaction enthalpy and entropy

Illustratively, the value of the re/de-hydrogenation enthalpy (∆H) is an important indicator to measure the strength of the Mg-H bond. The strong of the Mg-H bond following the large of the absolute value of ∆H. The pressure-composition-temperature (PCT) curve can be obtained by calibrating the PCT equilibrium point in the process of hydrogen ab/de-sorption. The relationship between plateau pressure (P_eq) and temperature (T) in the PCT curve can be described by the van’t Hoff equation [215-217]:

(4.2.3.1) \ln \left(\frac{p_{eq}}{P_0}\right)=\frac{\text{Δ}H}{RT}-\frac{\text{Δ}S}{R}

In this formula, P₀ is the atmospheric pressure (1.01×10⁵ Pa); ∆H and ∆S are the enthalpy and entropy of the hydrogen ab/de-sorption, respectively; and T is the absolute temperature; R is the gas constant (R=8.314 J·mol⁻¹·K⁻¹). According to the linear fitting between lnP and 1000/T, ∆H and ∆S can be calculated [39,218-220].

5. Investigation on design of Ti-based additives

The refined regulation of active structures and active sites in catalysts is important for catalyst design and has promising in fabricating the performance in hydrogen storage field [221-223]. Methods for changing thermodynamic and kinetic properties of energy storage functional materials have attracted great interest [140,224]. Extensive work has been done on boosting hydrogen storage performance of MgH₂ [225-228]. The in situ formation of MgH₂ with small sizes without Ti element was synthesized and used hydrogenation at room temperature, which conveyed excellent hydrogenation variables [229]. Additionally, ultrafine MgH₂ NPs were successfully fabricated without supports. The no Ti element materials conveyed excellent hydrogen storage for MgH₂ compared with nonconfined ultrafine MgH₂ [148]. The corresponding nano-structure has the ability to exert influences on the properties of solid hydrogen storage materials. Generally, the addition of additives or other catalysts has the ability to decrease the energy of metal-H bonds and reduce the reaction energies of MgH₂ [230,73]. Among all the additives, unique electrical and chemical properties of Ti-based materials make them promising for MgH₂ [90,91,71]. For example, many Ti-based materials, such as, MgH₂-TiN [231], MgH₂-Ti [232,233] and MgH₂-TiO₂ [234,235], MgH₂-TiF₃ [236-238] have been done in boosting hydrogen storage performance of MgH₂. Thus, the summaries of the Ti-based materials are helpful for the development of the hydrogen economy and provide corresponding theoretical guidance for the researches in different fields.

5.1 Designs aimed at providing active sites

Metallic titanium (Ti) has been used in the research on hydrogen storage and presents excellent performance in elevating the performance in the field of hydrogen storage system [239-241]. Ti-added MgH₂ alloys (MgH₂-12Ti) present excellent performance in MgH₂ system. The generated γ-MgH₂, TiH_1.924, and MgO during the process of reactive mechanical grinding is responsible for the enhancement of the hydrogen storage performance [242]. Ti element was added into MgH₂ by milling in hydrogen atmosphere and reactive mechanical grinding of MgH₂ with Ti decreases particle sizes and the formed β-MgH₂, γ-MgH₂, TiH_1.924, MgO, and MgTi₂O₄ improve the hydrogen storage performance [243]. Mg-Ti materials with different Ti contents were synthesized via inert gas condensation with Mg and Ti and conveyed excellent performance [193]. Mg-Ti-H NPs were prepared by gas phase condensation of Mg-Ti vapors under H₂ atmosphere. The increasing Ti content boosted the hydrogen storage activity [244]. AlCl₃/Ti co-doped 4MgH₂-Li₃AlH₆ was designed by solid ball-milled method and presented excellent dehydrogenation performance and the activation energy have a decrease [245]. The synthesized Mg_xTi_1−x thin films conveyed a hexagonal close packed (HCP) structure, the generation of nanometer-sized clusters of Mg presented a lower desorption temperature [246]. MgH₂-5 at% Ti-Mn-Cr was obtained through co-milling of MgH₂ with Ti-Mn-Cr alloy and the material presented excellent desorption temperature of mechanically activated MgH₂. The homogeneous distribution of the alloyed elements play an improtant role for enhancing the performance during the field of hydrogen storage [247].

Titanium hydrides (TiH_x) garner significant attention for storing hydrogen due to their strong hydrogen affinity, superior catalytic efficiency, and affordability. Specifically, in the dehydrogenation phase, the formation of stable and metastable titanium hydrides is advantageous for producing the hydrogen product and metal Ti [112]. Calculations using DFT reveal that the metastable hydrides in the system of MgH₂-TiH₂ possess minimal hydrogen binding energy, rendering them better suited for storage in lower temperature hydrogen environments. The MgH₂-TiH₂ system undergoes significant plastic deformation (SPD) using the high-pressure torsion (HPT) technique. Due to the creation of nanostructured ternary Mg-Ti-H hydride, the dehydrogenation temperature achieved is less than that of TiH₂ [248]. The catalytic role of TiH₂ in enhancing the hydrogen sorption kinetics of MgH₂ has been systematically demonstrated. Through gas-phase condensation of Mg/Ti vapors in a controlled He/H₂ environment, we successfully engineered biphase nanostructured composites comprising immiscible MgH₂ and TiH₂ domains. The incorporated TiH₂ phase exhibits dual functionality, demonstrating exceptional catalytic activity for hydrogen molecule dissociation/recombination while simultaneously creating rapid hydrogen diffusion pathways within the composite system (Fig. 12a) [249]. The in situ generation of TiH₂ additive in Ti/MgH₂ system are conducted and the formation of stable TiH₂-x transforms to TiH₂ upon recycling the powder during hydrogen storage process [250]. The disparity in lattice structure between Mg and TiH₂ hydride hinders the growth of Mg grains, maintaining the rapid absorption rate of the MgH₂-TiH₂ nanocomposite during its cycling [251] (Fig. 12b, 12c). Hydrogen desorption in MgH₂-TiH₂ composite was investigated and the NPs displayed a small absorption-desorption pressure hysteresis even at low temperatures [252] (Fig. 12d, 12e). Furthermore, the intimate interface between TiH₂ and MgH₂ was studied and promoted H₂ desorption from MgH₂ [253]. The MgH₂-TiH₂ composite synthesized through high-energy reactive ball milling (HRBM) of Mg and Ti under hydrogen atmosphere exhibited enhanced hydrogen storage performance with superior capacity and accelerated hydrogen absorption/desorption kinetics [254-257]. Additionally, nano-TiH_1.971 were prepared and present excellent performance, which remained stable in cycling and can serve as an active site for hydrogen transportation, thus boosting hydrogen storage properties of MgH₂ [258]. Mg-Ti-H films are also investigated and used in the hydrogen storage system [191]. Theoretical calculations have identified TiH₄ and VH₄ metal tetrahydrides as high-capacity hydrogen-storage materials, demonstrating exceptional dehydrogenation performance [259]. Illustratively, the noble metal as the co-additives was expressed outstanding performance of hydrogen storage of MgH₂. The addition of Pd and TiH₂ improved the dehydrogenation performance of MgH₂. 2MgH₂-TiH₂-0.1Pd composite decrease the dehydrogenation temperature of when compared with pristine MgH₂ and 2MgH₂-TiH₂. This result confirm that the introduction of noble metal co-additives has the ability to enhance the hydrogen storage performance [260]. The incorporation of graphite into nano-MgH₂-TiH₂ composites has been systematically investigated, revealing a remarkable enhancement in hydrogen storage performance [256].

5.2 Designs aimed at promoting electron transfer

Transition metals (TMs) and the corresponding compounds have been reported endow an effective influence on boosting hydrogen storage properties of MgH₂. TMs and their oxides have the ability to increase the hydrogen storage performance of MgH₂ [261,262]. Many works have been done in the field of hydrogen storage of MgH₂. 2D graphene-like TiO₂ (B) nanosheets was achieved as a highly efficient catalyst play a vital role in enhancing hydrogen storage properties of MgH₂ and Mg-TiO₂ composite presented excellent performance [263]. TiO₂ nanosheets with high-surface-energy {001} facets were synthesized and present excellent hydrogen storage properties of MgH₂ [72]. The enhancement is ascribed to the effect of nano-size and active {001} facets of anatase TiO₂ (Fig. 13a, 13b). Moreover, the ball-milled MgH₂-TiO₂ with different morphologies was investigated and shown excellent hydrogen storage performance [264]. The reduced Ti containing in MgH₂/TiO₂ was prepared and its effect on hydrogen storage behavior of MgH₂ was studied. The TiO₂ NPs supported on 3D ordered macro-porous structure [265] and dispersed metal NPs on TiO₂ [104] were synthesized and improved the hydrogen storage performance of MgH₂. The results proved that the reduced Ti oxide phases presented promise in promoting the dehydrogenation performance of MgH₂ system [266]. The effect of chemical interaction between MgH₂ and TiO₂ on the hydrogen storage performance of MgH₂ was investigated and the results confirm that passive MgO can as an active in-built catalyst and boosting the dehydrogenation kinetics [267]. Black TiO_2−x reduced by KH (K-TiO_2−x) was added and used on the hydrogen storage performance of MgH₂. The doped system present excellent performance in hydrogen storage of MgH₂ at room temperature [268]. MgH₂ ball milled with rutile and anatase TiO₂ were studied and the results confirm that rutile TiO₂ convey an excellent performance and decrease the apparent activation energy for desorption [269]. MgH₂/TiO₂ heterostructure was successfully fabricated via solvothermal strategy and shows rapid desorption kinetics. The abundant oxygen vacancies significantly improve the electrical conductivity of TiO₂ and offer active substance for the transportation of electrons and hydrogen, thus enhancing hydrogen sorption kinetics [93]. Additionally, TiO catalyzed Mg-MgH₂ was also design and conveyed a reduced apparent activation energy, thus improving the kinetics of hydrogen storage performance [270].

Additionally, carbon materials, such as, graphene, carbon nanotubes, have been proved to possess positive effect in improving cycling property during hydrogen storage process [271-273]. Although doping nano-catalyst is considered as an effective method to boost kinetics properties of hydrogen storage materials, the NPs generally suffer from agglomeration and inactivation during the process of hydrogen storage. Effective strategies are necessary to prepare nano-catalysts with high-efficiency. Carbon-supported TiO₂ (TiO₂@C) as an additive reduced the dehydrogenation operating temperatures. And the results of DFT calculations confirm that extended bond lengths and reduced bond strengths for Mg-H bonding exist when MgH₂ adsorbs on TiO₂ clusters, and boosting the hydrogen storage performance [274] (Fig. 13c-13f). 3D flower-like TiO₂@C and TiO₂ were synthesized and used for MgH₂ system, the existence of amorphous carbon prevented the aggregation and growth of materials and reduced the desorption activation energy of H in MgH₂ [96]. Monodispersed single-crystal-like TiO₂ NPs are supported in amorphous carbon and exhibit excellent catalytic hydrogen storage performance of MgH₂. And the existence of carbon protects the NPs and the synergistically catalytic roles of in-situ formation of TiO₂ NPs, amorphous carbon and multi-valence Ti species in the nano-catalyst boost the hydrogen storage performance [275]. MWCNTs decorated with TiO₂ (MWCNTs-TiO₂) is achieved and improved the dehydrogenation kinetics of 2LiBH₄-MgH₂ [276]. Additionally, nanosized lithiated titanium oxide (Li_xTiO₂) was prepared and the existence of Li_xTiO₂ can reduce the time required for the first dehydrogenation [277]. Ni/TiO₂ nanocomposite synthesized via solvothermal method enhanced the reversible hydrogen storage properties of Mg-based materials [95].

In nutshell, the TiO_x have many positive effects on the hydrogen storage of Mg-based materials. Through the rational design of the Ti-based materials, we can develop the materials in the field of hydrogen storage system. However, there are many works that should be done in order to research the catalytic structure, catalytic performance and catalytic mechanism. Therefore, the investigation of high-efficiency materials is significant for the development of the field of various fields.

Titanium-carbon composites (TiC_x) have been used in hydrogen storage systems. MXenes as a TiC_x composites have been used as high-efficiency catalysts for MgH₂-based hydrogen storage material [278,279]. The preparation of MXenes needs certain amount of HF to etch out the Al layers from the transition metal aluminum carbides or nitrides (MAX) phases and these may have effect on environment [280,281]. Ti₃AlCN MAX was applied directly to enhance kinetics and cycling stability of MgH₂. With addition of Ti₃AlCN, the onset dehydrogenation temperature of MgH₂ has an obvious decrease [282]. The phase composition and dehydrogenation performance of the composites are investigated based on Mg/MAX. The MAX-phase reduces the dehydrogenation temperature of MgH₂ [283]. Additionally, a MAX-phase carbide (Ti₃AlC₂) was prepared and the reaction effects of the as-prepared Ti₃AlC₂ on the hydrogen storage performance of MgH₂ were studied [284]. From the above-mentioned results, the MAX-phase carbide presents excellent performance for the hydrogen storage system. However, the etching of Al layer has the ability to convey another effect on hydrogen storage performance. Some other transitional metal carbides, such as, Ti₃C₂ [285,286], Ni₃C [287], Mo₂C [288,289], and NbC [290,291] were synthesized to improve hydrogen storage behaviors of MgH₂-based materials. MgH₂-Ti₃C₂ shows optimized hydrogen storage performance (Fig. 14a, 14b) [292]. The surface Ti atoms on prepared Ti₂C MXene with multivalence can serve as intermediate for electrons shifting between H⁺ and Mg²⁺, thus improving the hydrogen release temperature, activation energy and the overall changes on aspects of enthalpy [293]. Dispersed MgH₂ NPs anchored on 3D Ti₃C₂Tx (Ti-MX) was synthesized and the nano-size effect generated by nano-confinement and multiphasic interfaces between MgH₂ (Mg) and Ti-MX were responsible for superior hydrogen sorption performances [40] (Fig. 14c, 14d). A 2D Ti₃C₂ precursor presents superior catalytic performance towards the hydrogen storage reaction of MgH₂ [294]. MgH₂/5TiC/5Fe12Cr have superior hy/de-hydrogenation characteristics, following by a lower value of the activation energy. The enhanced catalytic performance is attribute to the synergistic effect of TiC/FeCr [295]. Furthermore, Ti₃C₂-supported praseodymium (III) fluoride (PrF₃) NPs (PrF₃/Ti₃C₂) exhibited excellent hydrogen storage performance toward MgH₂. The onset temperature of dehydrogenation and the activate energy have an improvement during the process of the hydrogen storage system. The experimental findings indicate that the hydrogen storage characteristics of MgH₂ are attributed to electron transfer mechanisms within Ti-based species and the synergistic coupling effects between Ti-species and PrF₃ [92]. TiC_X decorated on Mg NPs is designed and shown enhanced hydrogen storage kinetics of the nanocomposite because of synergistic effects of carbon confinement nanostructure [296]. In nutshell, TiC_x-based composites convey excellent performance on the hydrogen release of MgH₂. There are many works remains to be done for the enhancement of the catalytic performance.

5.3 Designs aimed at creating synergistic effects

Polymetallic Ti-based compounds also exhibited excellent performance in hydrogen storage materials. Ti−Cr−V alloys were synthesized and Mg-20 wt % Ti_0.16Cr_0.24V_0.6 possess the lowest hydrogen desorption temperature [297]. Ni/Ti₃C₂T_x composites were also prepared and presented excellent performance of MgH₂ [298]. Ultrafine bimetal NbTi nanocrystals were formed in situ following the ball milling of NbTiC MXene with MgH₂. The sample starts releasing hydrogen from 195 ℃. DFT analyses elucidate that Ti-to-Nb charge redistribution within NbTi clusters significantly enhances the hydrogen storage reactivity of MgH₂ [299] (Fig. 15a-15d). The TiMn₂ intermetallic phase was strategically incorporated as a catalytic additive into MgH₂, with the 10 wt% composite configuration demonstrating superior hydrogen sorption kinetics through enhanced interfacial charge transfer mechanisms [300] (Fig. 15e, 15f). TiFe as an additive was obtained and then doped into MgH₂ through ball milling, then used to improve the de/re-hydrogenation properties of MgH₂. The results confirm that the addition of TiFe boosted the hydrogen storage properties of MgH₂ because of the existence of TiFe and CNTs [135]. Mg-TiFe_0.8Mn_0.2-graphite [301] and metallic glassy Ti₂Ni are also used for enhancing the hydrogenation/dehydrogenation kinetics of MgH₂ [302]. V or Ti-V-Cr alloy [303,304]; Ti, Zr, Al and C (Mg-Al-Ti-Zr-C powders) [305]; Zr_0.4Ti_0.6Co nanosheets and carbon nanotubes [306], nano-Ti [307], improved hydrogen storage performance of Mg-based materials. Additionally, the other Ti-based additives such as transition metal sulfides (MgH₂-TiS₂) [308] and TiB₂ [309] also improved the reversible dehydrogenation properties of MgH₂. Thus, it is significant for the development of materials with high-efficiency catalytic performance based on polymetallic Ti-based compounds.

The support as the framework of the active substance in catalysts has the advantages of supporting active components, dispersing active ingredients, and increasing the strength of the catalyst [310-313]. The designed catalysts with supports have promising in balancing the high dispersion and high efficiency [139,314]. In the fields of hydrogen storage, the supports have many applications. Ni/Ti₃C₂ with interfacial differences were synthesized by wet chemical method and the electron transfers in multiple valence Ti and unique structure of Ni/Ti₃C₂ enhanced the hydrogen storage performance [98]. Ni@C materials supported on Ti₃C₂ MXene as a catalyst boosted the hydrogen desorption of MgH₂. The excellent performance is assigned to the formed Mg₂NiH₄ and metallic Ti NPs [139]. The remarkable catalytic effects of Ti₃C₂ MXene-based materials (Ni@Ti-MX) and the core−shell nanostructured MgH₂@Mg₂NiH₄, the above-mentioned demonstrated that the interfacial coupling effects from different interfaces of catalyst-matrix boosted the hydrogen storage performance (Fig. 16a, 16b) [315]. MOF-derived Ni NPs dispersed on MXene was used for improving hydrogen storage kinetics of MgH₂ and corresponding mechanism are also studied [101]. Effect of few-layer (FL) Ti₃C₂T_x supported nano-Ni on hydrogen storage performance of MgH₂ was researched. FL-Ti₃C₂T_x acts as a supporting material and self-assembles with Ni²⁺ assisting in the reduction of nano-Ni. The combined effects of nano-Ni on FL-Ti₃C₂T_x, large specific area of FL-Ti₃C₂T_x, multiple-valence Ti, and electronic interaction between Ni and FL-Ti₃C₂T_x greatly facilitated the hydrogen storage performance of Mg-based materials [316] (Fig. 16c, 16d). TiO₂/MXene heterostructures were obtained through one-step self-assembly. Abundant electrons from multiple valence Ti effectively enhance the reversible reaction of MgH₂ [97]. A sandwich like Ti₃C₂/TiO₂(A)-C prepared through gas-solid strategy was introduced into MgH₂ through the operation of ball milling and conveyed excellent catalytic effect on hydrogen storage of MgH₂, the enhancement of hydrogen storage performance was due to the synergistic catalysis between Ti₃C₂ and TiO₂(A)-C [317]. Graphene-supported FeOOH nanodots (FeOOH NDs@G) were prepared through a simple hydrothermal strategy and then introduced into MgH₂, which decrease the dehydrogenation and hydrogenation performance of MgH₂. The excellent hydrogen storage performance of FeOOH NDs@G towards MgH₂ is responsible for the synergistic effect between graphene nanosheets and the in situ generated Fe (Fig. 16e, 16f) [318].

To sum up, from the above-mentioned research, the Ti-based metals as the additives are summarized and the corresponding catalytic performance are also studied. However, the disadvantages of stable thermodynamics and poor kinetics limit the practical application of MgH₂. Therefore, the rational design strategy, such as, optimization of crystal structure, control of grain size and introduction of doping elements to improve the thermodynamics and dynamics is of significance for the performance of Mg-based hydrogen storage materials. Based on the experimental-theoretical results, the real reaction mechanism can be obtained and provide the guidance for the future design for the next-generation of hydrogen storage materials.

5.4 Designs aimed at destabilizing thermodynamics

Titanium fluoride compound (TiF_x, x=4, 3, and 2) has been used to study the performance of hydrogen storage materials, such as MgH₂, Mg(BH₄)₂, and Mg(AlH₄)₂ [319]. MgH₂+TiF₄ composites were prepared and the characterized for their structural, morphological and thermal properties were studied [320]. A mixture of Mg-Al-Ti-F-doped MgH₂ is designed and prepared through high-energy ball milling [321]. The corresponding results show that TiF₄ as an additive presented lower onset desorption temperature compare to pure MgH₂. The addition of NbF₅ or TiF₄ to Ca(BH₄)₂+MgH₂ was conducted to harvest a full reversible system [322]. The synergetic catalytic effect of TiF₃ and Nb₂O₅ was also investigated [323]. Additionally, TiFx composites were used in mixed hydrogen storage system. The addition of K₂TiF₆ was introduced into hydrogen storage properties of MgH₂+NaAlH₄ and presented excellent hydrogen storage properties compared to undoped composites [324]. K₂TiF₆ composites were used in enhancing the hydrogen storage properties of 4MgH₂-Li₃AlH₆ composite [325]. TiF₃ was used as an additive to improve the hydrogen storage properties of ternary-hydride system of NaAlH₄-MgH₂-LiBH₄ [326], destabilized MgH₂-Sn system [327], Mg₉₀Al₁₀ system [328], 4MgH₂-Na₃AlH₆ system [329]. Additionally, the combination of TiF_x and carbon species were operated to boost the hydrogen storage performance. The composites of high-energy ball milling with multi-wall carbon nanotubes (MWCNTs) and TiF₃ [330], multi-wall carbon nanotubes supported nano-nickel and TiF₃ addition [331], TiF₄ and MWCNTs [332] were synthesized and significantly decreases the dehydrogenation temperature of MgH₂. The Ni-decorated multi-walled carbon nanotubes (Ni/MWCNTs) demonstrating enhanced catalytic functionality when incorporated into MgH₂ through a combined process of hydriding combustion synthesis and mechanical milling. Subsequent introduction of TiF₃ into the Mg-Ni/MWCNTs composite system demonstrated markedly enhanced hydrogen sorption kinetics.

In a nutshell, the effect of Ti-F derivatives, such as, TiF₄, TiF₃ and TiF₂, on hydrogen storage performance was studied to elucidate the effect of F for the catalytic reaction. The F^- anion plays a key role in improving the dehydrogenation properties. The strong chemical interaction between TiF_x and MgH₂ has the ability to boost the formation of TiH₂ and Ti-Mg-F species and thus enhances the hydrogen storage kinetics of MgH₂.

Additionally, Ti derivatives based on metals have aroused much attention because of their unique physical and chemical properties. The titanium derivatives based on metals have also been shown to have a positive effect on hydrogen storage materials. Hamamelis-like structure of K₂Ti₆O₁₃ is synthesized by alkali treatment of MXene, which exhibits excellent catalytic performance for hydrogen storage from MgH₂. MgH₂ reacts with K₂Ti₆O₁₃ during ball milling and produces KMgH₃, TiO, and Ti. In addition, O or Ti deficiencies in TiO boosts the hydrogen storage properties of MgH₂ [333] (Fig. 17a-17c). Ultrathin K₂Ti₈O₁₇ was obtained using TiO₂ and KOH as resources and conveyed an excellent hydrogen storage of MgH₂ [91]. Na₂Ti₃O₇ nanotubes (NTs) and Na₂Ti₃O₇ nanorods (NRs) is prepared via hydrothermal and solid-state strategies, respectively. Comparing with bulk MgH₂ and MgH₂-Na₂Ti₃O₇ NRs composite, MgH₂-Na₂Ti₃O₇ NTs has an excellent performance in hydrogen storage system [334]. Na₂Ti₃O₇ with rich oxygen vacancies (Na₂Ti₃O₇-O_v) was designed from Ti₃C₂ MXene, and confirm an enhancement to the hydrogen storage performance of MgH₂. Both experimental and theoretical calculations results verified that oxygen vacancies in Na₂Ti₃O₇-O_v reduce the activation energy during MgH₂ hydrogen storage and convey an excellent hydrogen storage kinetics [90] (Fig. 17d, 17e). A bimetallic Ti-Nb oxide of TiNb₂O₇ with high surface area was synthesized and shown excellent catalytic effect for MgH₂ hydrogen storage [335] (Fig. 17f, 17g). TiVO_3.5 as an active catalytic precursor presents excellent performance for improving hydrogen storage properties of MgH₂ [71]. Research on Mg₂TiO₄, MgTiO₃ and TiO₂ additives incorporated MgH₂ were operated to investigate the corresponding performance. These results confirmed that in situ generation of reduced Ti containing active species play an important role in the hydrogen storage performance of MgH₂ [336]. BaTiO₃ plays an effective role in the hydrogen storage process of MgH₂ [337,338]. TMTiO₃ (TM = Ni and Co) are synthesized and introduced into MgH₂ system and the corresponding TMTiO₃ exhibited perfect reaction effect on the hydrogen desorption performance of MgH₂ [99]. NiTiO₃ materials with different mole ratio of Ni to Ti were reported and doped into Mg to enhance its hydrogen storage properties. Mg-NiTiO₃/TiO₂, the nanosizing and catalyst doping led to a synergistic effect on the enhanced hydrogen storage performance of Mg-NiTiO₃-C [134]. Additionally, MgH₂ doped with Li₂TiO₃ also convey excellent performance in hydrogen storage system and started to release hydrogen at 170 ℃, which is lower than that of the as-milled MgH₂ [339]. Table 3 was the performance comparison based on different Ti-based materials.

5.5 Conclusion and reflection of Ti-based materials

The investigation on design of Ti-based additives, such as, metallic Ti-based materials, titanium oxides-based materials, titanium-carbon composites, titanium hydrides, titanium fluoride compounds, titanium derivatives, polymetallic Ti-based compounds, and materials supported on Ti-based additives was summarized. (1) Catalysts design based on “hydrogen pump” effect, such as, metal Ti NPs, TiH_x, and some Ti-carbon composites, the core effect of these catalysts is to provide efficient hydrogen dissociation/interfaces and fast hydrogen atom diffusion channels to improve the kinetics. (2) Catalytic designs using “multiple valence titanium mechanism”, such as titanium oxide, titanium fluoride, and other titanium derivatives. The Ti ions in these compounds have the potential to change valence in the reaction, which can promote the heterocleavage and dissociation of hydrogen atom and boost kinetics. (3) The design of Ti-carbon composites and supported materials have the ability to limit the growth of Mg particles, disperse Ti-based catalyst and prevents agglomeration, thus significantly improving kinetics and cycle life. (4) The introduction of synergistic effect is important for the design of materials. Such as, polymetallic Ti-based compounds, the introduction of second or more metal elements will generate a synergistic catalysis effect with Ti element, which is significance to reduce reaction barriers and improve reaction kinetics. In conclusion, the comprehensive improvement on dynamic performance and cycle life is an important direction for large-scale application in the field of hydrogen storage in the future. The detailed reflection was as follows,

(1) Summary on Ti-based materials. The above-mentioned Ti-based materials presented excellent hydrogen storage performance of MgH₂. The special electronic structure and crystal structure of materials has the ability to boost the adsorption, dissociation and recombination of hydrogen molecules, and accelerate the progress of hydrogen absorption and release reactions. Moreover, the introduction of Ti-based materials will have promised in refining the grains and introducing lattice defects, promoting the diffusion and reaction of hydrogen atoms in the material, and improving their kinetic properties. Additionally, Ti-based additives have excellent chemical and thermal stability in the process of hydrogen absorption and release, and can maintain the relative stability of the structure and properties, and thus ensure the long-term effectiveness of the additives.

(2) Future research direction. Developing new Ti-based additives with higher catalytic activity and selectivity is an important role in the hydrogen storage system. Currently, preparation strategies have problems such as complex process, high cost and low output, which limit their large-scale application. By optimizing the process through the introduction of high entropy catalysts, flash firing method and mechano-chemical synthesis method to obtain the additives, and improve their feasibility in the field of actual hydrogen storage. Additionally, although there is certain understanding of the action mechanism of Ti-based additives in hydrogen storage, further research is still needed. The advanced characterization techniques, such as in situ X-ray diffraction, high-resolution transmission electron microscopy, DFT calculations, and so on, have been promising in revealing the interaction mechanism between additives at the atomic and electronic levels, and providing a more solid theoretical basis for the optimal design of additives.

(3) Inspiration for researchers. The application of Ti-based additives in hydrogen storage involves materials science, chemistry, and physics. On the basis of in-depth study of the action mechanism of Ti-based additives, translating the results of basic research into practically usable hydrogen storage materials and technologies. Additionally, a systematic research approach is required when studying the performance of Ti-based additives in hydrogen storage. Considering the influence of multiple factors such as type, content, preparation process of additives on the hydrogen absorption and release conditions on the performance of the system is significance to provide comprehensive and accurate reference for follow-up research.

6. Final summary and future outlook

The hydrogen storage materials based on MgH₂ have promising in hydrogen station, hydrogen-electric energy storage station, hydrogen chemical industry, hydrogen power/hydrogen energy storage power generation system and so on [340,341]. This review summarized advanced insights into Ti-based materials for MgH₂ hydrogen storage, which consists of design paradigms, activity evaluation and mechanism elucidation. Many works should be done in improving the dynamic and thermodynamic catalytic performance of Mg-based hydrogen storage materials. And challenges still remain in the further research of Mg-based composites system. With the rapid development of new generation of information technology and intelligent manufacturing, high quality and high activity for Mg-based materials are the dominating development direction. Based on this review, the rational suggestions for design paradigms, activity evaluation and mechanism elucidation are proposed as follows (Fig. 18),

6.1 Innovative design of Ti-based additives

Currently, Ti-based additives have many researches in the field of hydrogen storage. Upcoming studies aim to eliminate sizable particles and incorporate high-efficiency catalysts into synthesis, thereby improving the kinetics of absorption and desorption for practical use. Developing novel synthetic strategy to realize the accurate position control of additives on the surfaces of MgH₂ hydrogen storage materials and thus maximizing the catalytic effect of the additives under the optimal hydrogen storage capacity of Mg-based hydrogen storage system is crucial for developing hydrogen storage system. Moreover, noble-metal-based materials as co-additives to boost the catalytic performance of hydrogen storage system and the corresponding mechanism can be also investigated. Such as, (1) SACs, when it in contact with MgH₂, these sites can dissociate extremely efficiently hydrogen molecules, significantly reducing the reaction energy barrier [342]. DFT simulations confirmed that single atoms can significantly change the local electronic structure and weaken the Mg-H bond, thereby improving the thermodynamic stability [343,344]. The challenge is to controllably synthesize high-load SACs with high dispersion on a large scale. (2) High-entropy alloy catalysts (HEAs) have the advantage of high entropy effect and lattice distortion [345,346]. HEAs can change the components, and electronic structure of catalysts, thereby optimizing its interaction strength with hydrogen, which allows HEAs to maintain the stability of phase structure and catalytic activity [347-350]. However, the multi-component making it difficult to clarify the specific role of each element, and elucidate catalytic mechanism.

6.2 Characterizations of MgH₂ composites in hydrogen storage system

The characterizations of MgH₂-based composites in hydrogen storage system are necessary to study their materials structures, thermal and structural stability, chemical compositions environment and the others. The results achieved from methods such as XRD, XPS, SEM, TEM and so on are common strategy to achieve the materials [351]. For materials, the common characterizations still have some challenge in the development of the investigation of performance and mechanism. The hydrogen absorption and release process is a dynamic, non-equilibrium process, conventional characterization is mostly performed before and after the reaction, which can provide a static snapshot. This will lead to the loss of key information during reaction process. Mg and MgH₂ are very reactive and highly susceptible to air oxidation to form a magnesium oxide (MgO) surface layer, which can seriously interfere with the analysis of real surfaces. The characterization of HRTEM also has the possible to alter material structure. The type and reactivity of the phase structure present on the surface of materials can determine the macroscopic reaction performance of the hydrogen storage materials. Thus, in situ/Operando characterization is the most important direction to observe dynamic processes in real time. Additionally, the application of multi-technology combination (integrates spatial, temporal and energy information), the combination of theory and experiment, and the others is necessary for the analysis of hydrogen storage field. Thus, the excavation of in situ or Operando spectroscopy analyses technologies have promising in leading to unprecedented advantages on the solid-state hydrogen storage system.

6.3 Investigation on structure-activity relationship of hydrogen storage system

Development of efficient and stable Ti-based metal materials is the key to analyzing the microscopic reaction kinetics in hydrogenation/dehydrogenation reaction and the dynamically evolving behavior during the environment. Through the rational regulation of hydrogen storage materials on the structures to generate more active substances and increase abundant active sites is of significance for enhancing hydrogen storage performance of Ti-based materials. Combining relevant spectroscopic characterizations, the relationship between species configuration and reactive properties of hydrogen storage materials can be harvested from the atomic level. The investigation on structure-activity relationship of hydrogen storage system provides the theoretical guidance for excavating high-efficiency materials. However, developing efficient hydrogen storage materials urgently requires understanding the active source of active sites in hydrogen storage system due to the uncertainty of structure-activity relationship and complex and changeable influencing factors of hydrogen storage system. Thus, the identification of reactive sites to establish a clear relationship between atomic structure and catalytic performance is helpful for rational improvements and design of hydrogen storage materials. Illustratively, it is necessary to combine the characterization and performance testing, and seen them as an interlocking chain of evidence that collectively points to a scientific conclusion. Finally, with strict logical language and theoretical calculations to reveal the structure-effect relationship.

6.4 Construction of diversified hydrogen storage system

With the development of technology and application, solid-state hydrogen storage system plays an important position in the diversified hydrogen energy storage and transportation system in future. In particular, the hybrid hydrogen storage system is a new research direction and development of hydrogen storage materials in the future. The hybrid hydrogen storage system has the ability to develop safe and efficient composite hydrogen storage materials as premise to achieve large-scale preparation and recycling of hydrogen storage materials, such as hybrid hydrogen storage system derived from LiBH₄, NaAlH₄, KSiH₃, NaMgH₃, LiNH₂-LiH and so on. Additionally, investigation on Mg-based hydrogen storage device plays an important role in the hydrogen energy industry chain [352]. However, the limitations of Mg-based hydrogen storage technology in the construction of diversified hydrogen storage systems mainly stem from its own technical characteristics and application. The introduction of Mg-based hydrogen storage technology requires the renovation of existing infrastructure or the construction of new dedicated facilities, which incurs huge initial investment costs and conversion costs. Therefore, it is still a challenge to design hydrogen storage materials for specific purposes, which should be strengthened in future.

6.5 Development strategy of hydrogen storage technology

Creating materials for solid-state hydrogen storage, characterized by dense hydrogen storage and reduced dehydrogenation temperatures, represents a crucial path in advancing large-scale hydrogen storage and transportation technologies. Advancements in extensive hydrogen storage and transport technology are crucial for attaining the “carbon neutrality” objective and fostering energy transformation, a key factor in enhancing energy security. Within this framework, investigating new compositions of Ti-based compounds offers a hopeful avenue for enhancing solid-state storage efficiency. It is significance to employ sophisticated in-situ/operando characterization methods like synchrotron X-ray diffraction, neutron scattering, and Raman spectroscopy to clarify reaction routes and corresponding mechanistic discussions. Additionally, it is crucial to thoroughly assess the expandability and financial feasibility of synthesizing Ti-based catalytic substances to enhance their industrial incorporation into commercial hydrogen storage systems.

CRediT author statement

Huanhuan Zhang: writing - original draft, writing - review & editing, formal analysis. Yanping Fan: writing - review & editing, formal analysis. Shuyan Guan: formal analysis. Wen-Gang Cui: formal analysis. Mingchang Zhang: formal analysis. Zhenglong Li: formal analysis. Yuhai Dou: formal analysis. Jiarui Yang: formal analysis. Zechao Zhuang: formal analysis. Zhenluo Yuan: formal analysis. Shiqian Zhao: formal analysis. Dingsheng Wang: visualization, formal analysis, supervision, conceptualization. Baozhong Liu: project administration, visualization, formal analysis, supervision. Hongge Pan: visualization, formal analysis, supervision, conceptualization. All authors have given approval to the final version of the manuscript.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this article. Dingsheng Wang is an Editorial Board Member of this journal and he was not involved in the editorial review or the decision to publish this article.

References

[1] Zhang Xiaofei, Huang Wenhuan, Yu Le, García-Melchor Max, Wang Dingsheng, Zhi Linjie, Zhang Huabin. Enabling heterogeneous catalysis to achieve carbon neutrality: directional catalytic conversion of CO₂ into carboxylic acids, Carbon Energy 2024, 6, e362. https://doi.org/10.1002/cey2.362.

[2] Li Neng, Yang Yufei, Shi Zuhao, Lan Zhigao, Arramel, Zhang Peng, Ong Wee-Jun, Jiang Jizhou, Lu Jianfeng. Shedding light on the energy applications of emerging 2D hybrid organic-inorganic halide perovskites, Iscience 2022, 25, 103753. https://doi.org/10.1016/j.isci.2022.103753.

[3] Zhou Cheng. Mostafa Torka Beydokhti, Fatima Rammal, Parveen Kumar, Maxime Lacroix, Walter Vermeiren, Michiel Dusselier, Yuhe Liao, Bert F. Sels. Proximity-independent acid-base synergy in a solid ZrO_xH_y catalyst for amine regeneration in post-combustion CO₂ capture, Nature Catalysis 2025, 8, 270-281. https://doi.org/10.1038/s41929-025-01307-8

[4] Li Jing, Liu Xiang, Xu Si-Min, Xu Ming, Wang Yunlong, Lyu Yizheng, Li An-Zhen, Wang Ye, Wang Xi, Zhou Tiancong, Zhou Hua, Peng Yue, Li Xuning, Zheng Lirong, Duan Haohong. Sustainable oxime production via the electrosynthesis of hydroxylamine in a free state, Nature Synthesis 2025, 4, 1598-1609. https://doi.org/10.1038/s44160-025-00879-4.

[5] Shen Ji, Tang Minhao, Shi Zuhao, Guan Shuyan, Shi Yijie, Zhuang Zechao, Li Runze, Yang Jiarui, He Daping, Liu Baozhong, Dou Yuhai, Wang Dingsheng. Efficient generation of negative hydrogen with bimetallic-ternary-structured catalysts for nitrobenzene hydrogenation, Angewandte Chemie International Edition 2025, e202423626. https://doi.org/10.1002/anie.202423626.

[6] Zhang Jiahao, Fu Xianbiao, Kwon Soonho, Chen Kaifeng, Liu Xiaozhi, Yang Jin, Sun Haoran, Wang Yanchang, Uchiyama Tomoki, Uchimoto Yoshiharu, Li Shaofeng, Li Yan, Fan Xiaolong, Chen Gong, Xia Fanjie, Wu Jinsong, Li Yanbo, Yue Qin, Qiao Liang, Su Dong, Zhou Hua, A William, Goddard, Kang Yijin. Tantalum-stabilized ruthenium oxide electrocatalysts for industrial water electrolysis, Science 2025, 387, 48-55. https://doi.org/10.1126/science.ado9938.

[7] Zhao Xinru, Liu Yanyan, Yuan Huiyu, Wen Hao, Zhang Huanhuan, Ashraf Saima, Guan Shuyan, Liu Tao, Mehdi Sehrish, Shen Ruofan, Guo Xianji, Fan Yanping, Liu Baozhong, Li Baojun. Coupling atom ensemble and electron transfer in PdCu for superior catalytic kinetics in hydrogen generation, Nano Research 2023, 16, 9012-9021. https://doi.org/10.1007/s12274-023-5667-1.

[8] Lu Zhiwen, Sun Wei, Cai Pingwei, Fan Linfeng, Chen Kai, Gao Jiyuan, Zhang Hao, Chen Junxiang, Wen Zhenhai. High-entropy alloy catalysts for advanced hydrogen-production zinc-based batteries, Energy & Environmental Science 2025, 18, 2918-2930. https://doi.org/10.1039/D4EE05500D.

[9] Zhang Zhuohan, Yu Zhichao, Liu Zhaoyang, Ma Lixiang, Wang Jing, Li Yuan, Zhang Lu, Han Shumin. Dual-functional Nb/Sm₃H₇ interface for enhanced hydrogen storage performance in Mg/MgH₂ system, Chemical Engineering Journal 2025, 526, 171131. https://doi.org/10.1016/j.cej.2025.171131.

[10] Zheng Yijuan, Xing Zhenyu, Xiao Sutong, Ye Daoping, Kong Yuxuan, Zhang Shuxin, Ma Tian, Cheng Chong, Li Shuang, Zhao Changsheng. Lattice-matched iridium on vanadium nitride as efficient hydrogen electrocatalyst, Advanced Materials 2025, 37, 2508994. https://doi.org/10.1002/adma.202508994.

[11] Kang Naixin, Wei Xiaorong, Shen Ruofan, Li Baojun, Cal Eduardo Guisasola, Moya Sergio, Salmon Lionel, Wang Changlong, Coy Emerson, Berlande Murielle, Pozzo Jean-Luc, Astruc Didier. Fast Au-Ni@ZIF-8-catalyzed ammonia borane hydrolysis boosted by dramatic volcano-type synergy and plasmonic acceleration, Applied Catalysis B: Environmental 2023, 320, 121957. https://doi.org/10.1016/j.apcatb.2022.121957.

[12] Gong Cheng, Li Weixin, Du Xing, He Xuan, Wang Daheng, Chen Hui, Fang Wei, Zhao Lei, Chai Yang. Manipulating spin polarization by in-situ reconstructed amorphous/crystalline CoFe-LDH for efficient electrocatalytic water splitting, Nano Research 2025, 18, 94907668. https://doi.org/10.26599/NR.2025.94907668.

[13] Zhu Anquan, Qiao Lulu, Liu Kai, Gan Guoqiang, Luan Chuhao, Lin Dewu, Zhou Yin, Bu Shuyu, Zhang Tian, Liu Kunlun, Song Tianyi, Liu Heng, Li Hao, Hong Guo, Zhang Wenjun. Rational design of precatalysts and controlled evolution of catalyst-electrolyte interface for efficient hydrogen production, Nature Communications 2025, 16, 1880. https://doi.org/10.1038/s41467-025-57056-6.

[14] Chen Zhigang, Zeng Hangyun, Zhang Chunyu, Cai Hang, Jiang Yaping, Hu Jiangyan, Wang Hongyu, Wang Juan, Cui Yi. Ru-Mo solid-solution catalyst for hydrogen evolution in alkaline electrolyte, Nano Research 2025, 18, 94907346. https://doi.org/10.26599/NR.2025.94907346.

[15] Chen Yue, Kong Xiao, Yang Chengsheng, Liao Yuhe, Gao Ge, Ma Rui, Peng Mi, Shao Weipeng, Zheng Heng, Zhang Hui, Pan Xin, Yang Fan, Zhu Yulei, Liu Zhi, Cao Yong, Ma Ding, Bao Xinhe, Zhu Yifeng. A catalytic cycle that enables crude hydrogen separation, storage and transportation, Nature Energy 2025, 10, 971-980. https://doi.org/10.1038/s41560-025-01806-9.

[16] Zhang Huanhuan, Liu Yanyan, Liu Shuling, Guan Shuyan, Shen Ruofan, Wen Hao, Cao Xiaoyu, Liu Baozhong, Jiang Jianchun, Li Baojun. Progress and perspective on heterogeneous catalysis of liquid formic acid dehydrogenation: coordination structure design, activity improvement, and mechanism insights, Advanced Materials 2025, 37, e09068. https://doi.org/10.1002/adma.202509068.

[17] Kumar Niraj, Lee Seul-Yi, Park Soo-Jin. Advancements in hydrogen storage technologies: a comprehensive review of materials, methods, and economic policy, Nano Today 2024, 56, 102302. https://doi.org/10.1016/j.nantod.2024.102302.

[18] Guan Shuyan, Shen Shijie, Dou Yuhai, Chen Wenwen, Shen Ji, Ye Bochao, Cui Wen-Gang, Zhong Wenwu, Li Zhenglong, Pan Hongge, Wang Dingsheng. Progress and perspectives on hydrogen storage and release in negative hydrogen medium, Energy & Environmental Science, 2025, 18, 9324-9372. https://doi.org/10.1039/D5EE04149J.

[19] Chu Chenyang, Wu Kai, Luo Bingbing, Cao Qi, Zhang Huiyan. Hydrogen storage by liquid organic hydrogen carriers: catalyst, renewable carrier, and technology-a review, Carbon Resources Conversion 2023, 6, 334-351. https://doi.org/10.1016/j.crcon.2023.03.007.

[20] Deng Jiayi, Li Yun, Ning Hua, Qing Peilin, Huang Xiantun, Luo Hui, Zhang Liang, Li Guangxu, Huang Cunke, Lan Zhiqiang, Zhou Wenzheng, Guo Jin, Wang Xinhua, Liu Haizhen. MXenes as catalysts for lightweight hydrogen storage materials: a review, Materials Today Catalysis 2024, 7, 100073. https://doi.org/10.1016/j.mtcata.2024.100073.

[21] Li Dongze, Liu Zhentao, Qiao Liang, Kong Xiaoyang, Wang Enhua, Li Haidong, Jin Lili, Wang Chunya, Xu Chunming, Wang Xilong. One-pot template-free green synthesis of mesoporous amorphous silica-alumina for enhanced hydrogen storage in naphthalene, Journal of Catalysis 2025, 452, 116411. https://doi.org/10.1016/j.jcat.2025.116411.

[22] Hou Gang, Zhang Bofeng, Xia Liming, Song Mingxia, Liu Guozhu. Structural modulation of Pt nanoparticles anchored by NiO_x on silica for enhanced methylcyclohexane dehydrogenation, ACS Catalysis 2025, 15, 19489-19502. https://doi.org/10.1021/acscatal.5c03362.

[23] Wei Duo, Shi Xinzhe, Qu Ruiyang, Junge Kathrin, Junge Henrik, Beller Matthias. Toward a hydrogen economy: development of heterogeneous catalysts for chemical hydrogen storage and release reactions, ACS Energy Letters 2022, 7, 3734-3752. https://doi.org/10.1021/acsenergylett.2c01850.

[24] Khan Darvaish, Ong Wee-Jun. Tailoring hydrogen storage materials kinetics and thermodynamics through nanostructuring, and nanoconfinement with In-situ catalysis, Interdisciplinary Materials 2025, 4, 249-283. https://doi.org/10.1002/idm2.12234.

[25] Zhang Chunmin, Liang Long, Zhao Shaolei, Wu Zhijian, Wang Shaohua, Yin Dongming, Wang Qingshuang, Wang Limin, Wang Chunli, Cheng Yong. Dehydrogenation behavior and mechanism of LiAlH₄ adding nano-CeO₂ with different morphologies, Nano Research 2023, 16, 9426-9434. https://doi.org/10.1007/s12274-023-5636-8.

[26] Li Yuting, Ding Zhao, Jiang Han, Lin Guo, Li Shaoyuan, Du Wenjia, Chen Yu’an, L. Shaw Leon, Pan Fusheng. Spatially programmed confinement catalysis enables high-performance magnesium hydrogen storage, Nano Lett. 2025, 25, 16801-16808. https://doi.org/10.1021/acs.nanolett.5c04450.

[27] Guan Haotian, Liu Jiang, Sun Xuan, Lu Yangfan, Wang Hongyuan, Luo Qun, Li Qian, Pan Fusheng. Titanium-nickel dual active sites enabled reversible hydrogen storage of magnesium at 180°C with exceptional cycle stability, Advanced Materials 2025, 37, 2500178. https://doi.org/10.1002/adma.202500178.

[28] Wang Renyuan, Yang Xijia, Chen Xunfeng, Zhang Xia, Chi Yaowei, Zhang Dan, Chu Shaohua, Zhou Pei. A critical review for hydrogen application in agriculture: Recent advances and perspectives, Critical Reviews in Environmental Science and Technology 2024, 54, 222-238. https://doi.org/10.1080/10643389.2023.2232253.

[29] Yang Hang, Ding Zhao, Li Yu-Ting, Li Shao-Yuan, Wu Ping-Keng, Hou Quan-Hui, Zheng Yang, Gao Biao, Huo Kai-Fu, Du Wen-Jia, L. Shaw Leon. Recent advances in kinetic and thermodynamic regulation of magnesium hydride for hydrogen storage, Rare Metals 2023, 42, 2906-2927. https://doi.org/10.1007/s12598-023-02306-z.

[30] Zhang Lingchao, Wang Ke, Liu Yongfeng, Zhang Xin, Hu Jianjiang, Gao Mingxia, Pan Hongge. Highly active multivalent multielement catalysts derived from hierarchical porous TiNb₂O₇ nanospheres for the reversible hydrogen storage of MgH₂, Nano Research 2021, 14, 148-156. https://doi.org/10.1007/s12274-020-3058-4.

[31] Zhang Qiuyu, Li Yinghui, Sun Fengzhan, Lin Xi, Hu Zhigang, Yang Haiyan, Zou Jianxin. Boosting hydrogen storage performances of MgH₂ by using a Ni-MOF derived Ni/NiO@C composite containing Ni/NiO nanoheterojunctions, Chemical Engineering Journal 2025, 525, 169631. https://doi.org/10.1016/j.cej.2025.169631.

[32] Huang Tianping. Enhancing hydrogen storage properties of MgH₂ through addition of Ni/CoMoO₄ nanorods, Materials Today Energy 2021, 19, 100613. https://doi.org/10.1016/.mtener.2020.100613.

[33] Ali Wajid, Li Xinyang, Yang Yuxiao, Li Na, Huang Bo, Wu Chengzhang, Ding Shujiang. in situ formed Ti/Nb nanocatalysts within a bimetal 3D MXene nanostructure realizing long cyclic lifetime and faster kinetic rates of MgH₂, ACS Applied Materials & Interfaces 2023, 15, 36167-36178. https://doi.org/10.1021/acsami.3c05308.

[34] Lan Zhiqiang, Fu Hong, Zhao Ruolin, Liu Haizhen, Zhou Wenzheng, Ning Hua, Guo Jin. Roles of in situ-formed NbN and Nb₂O₅ from N-doped Nb₂C MXene in regulating the re/hydrogenation and cycling performance of magnesium hydride, Chemical Engineering Journal 2022, 431, 133985. https://doi.org/10.1016/j.cej.2021.133985.

[35] Qin Yuanlong, Yu Kedi, Wang Guo, Zhuang Zechao, Dou Yuhai, Wang Dingsheng, Chen Zhengbo. Adjacent-ligand tuning of atomically precise Cu-Pd sites enables efficient methanol electrooxidation with a CO-free pathway, Angewandte Chemie International Edition 2025, 64, e202420817. https://doi.org/10.1002/anie.202420817.

[36] Wang Yao, Ma Fengya, Zhang Guoqing, Zhang Jiawei, Zhao Hui, Dong Yuming, Wang Dingsheng. Precise synthesis of dual atom sites for electrocatalysis, Nano Research 2024, 17, 9397-9427. https://doi.org/10.1007/s12274-024-6940-7.

[37] Chen Hao, Ma Yongbing, Wu Qilong, Xu Hanshuai, Zhang Lubo, Wang Xin, Lyu Xiao, Chen Jun, Jia Yi. Electrocatalysis for liquid chemical hydrogen storage, Coordination Chemistry Reviews 2025, 534, 216562. https://doi.org/10.1016/j.ccr. 2025.216562.

[38] Ding Xin, Chen Ruirun, Chen Xiaoyu, Fang Hongze, Wang Qi, Su Yanqing, Guo Jingjie. A novel method towards improving the hydrogen storage properties of hypoeutectic Mg-Ni alloy via ultrasonic treatment, Journal of Magnesium and Alloys 2023, 11, 903-915. https://doi.org/10.1016/j.jma. 2021.06.003.

[39] Ren Li, Li Yinghui, Zhang Ning, Li Zi, Lin Xi, Zhu Wen, Lu Chong, Ding Wenjiang, Zou Jianxin. Nanostructuring of Mg-based hydrogen storage materials: recent advances for promoting key applications, Nano-Micro Letters 2023, 15, 93. https://doi.org/10.1007/s40820-023-01041-5.

[40] Zhu Wen, Ren Li, Lu Chong, Xu Hao, Sun Fengzhan, Ma Zhewen, Zou Jianxin. Nanoconfined and in situ catalyzed MgH₂ self-assembled on 3D Ti₃C₂ MXene folded nanosheets with enhanced hydrogen sorption performances, ACS Nano 2021, 15, 18494-18504. https://doi.org/10.1021/acsnano. 1c08343.

[41] Liu Pei, Lian Jiajia, Chen Haipeng, Liu Xiaojing, Chen Yuanli, Zhang Tonghuan, Yu Hao, Lu Guojian, Zhou Shixue. In-situ synthesis of Mg₂Ni-Ce₆O₁₁ catalyst for improvement of hydrogen storage in magnesium, Chemical Engineering Journal 2020, 385, 123448. https://doi.org/10.1016/j.cej.2019. 123448.

[42] Zhou Dongsheng, Zheng Chunling, Zhang Yanghuan, Sun Hanfeng, Sheng Peng, Zhang Xin, Li Jun, Guo Shihai, Zhao Dongliang. An overview of RE-Mg-based alloys for hydrogen storage: structure, properties, progresses and perspectives, Journal of Magnesium and Alloys 2025, 13, 41-70. https://doi.org/10.1016/j.jma.2024.12.020.

[43] Halpren Ethan, Yao Xue, Wen Chen Zhi, Veer Singh Chandra. Machine learning assisted design of BCC high entropy alloys for room temperature hydrogen storage, Acta Materialia 2024, 270, 119841. https://doi.org/10.1016/ j.actamat.2024.119841.

[44] Zhao Xianzheng, Wang Hongyuan, Liu Jiang, Lu Yangfan, Guo Zhilin, Guan Haotian, Ding Zhao, Tan Jun, Li Qian, Wu Jiazhen, Pan Fusheng. Tunable metal-hydrogen bonding in Cu-Ru catalysts enables selective hydrogen storage reactions in Mg-based composite, Advanced Functional Materials 2025, 35, 2505352. https://doi.org/10.1002/adfm.202505352.

[45] Xia Guanglin, Zhang Lijun, Chen Xiaowei, Huang Yuqin, Sun Dalin, Fang Fang, Guo Zaiping, Yu Xuebin. Carbon hollow nanobubbles on porous carbon nanofibers: an ideal host for high-performance sodium-sulfur batteries and hydrogen storage, Energy Storage Materials 2018, 14, 314-323. https://doi.org/10.1016/j.ensm.2018.05.008.

[46] Zhang Jiguang, Zhu Yunfeng, Lin Huaijun, Liu Yana, Zhang Yao, Li Shenyang, Ma Zhongliang, Li Liquan. Metal hydride nanoparticles with ultrahigh structural stability and hydrogen storage activity derived from microencapsulated nanoconfinement, Advanced Materials 2017, 29, 1700760. https://doi.org/10.1002/adma.201700760.

[47] Zhao Yuan, Wang Qingshuang, Yin Dongming, Wang Xiaoli, Li Shouliang, Wang Chunli, Liang Long, Zhao Shaolei, Wang Limin, Cheng Yong. Hollow structured Fe@C nanorods for boosting dehydrogenation properties of α-AlH₃, Nano Research 2024, 17, 8184-8191. https://doi.org/10.1007/ s12274-024-6867-z.

[48] Zhao Duode, Hou Xiaojiang, Ge Yu, Sun Dongfeng, Li Danting, Wang Chenlu, Xie Xinlei, Zhu Peixuan, Ye Xiaohui, Suo Guoquan, Yang Yanling. Nanosizing enhancement of hydrogen storage performance and mechanism in Mg-based materials: nano-substrate modulation, nano-catalyst construction, and nano-catalytic mechanisms, Journal of Energy Chemistry 2025, 109, 609-636. https://doi.org/10.1016/j.jechem.2025.06.005.

[49] Liu Yu-Kun, Pang Yu-Chen, Li Chao-Qun, Zhang Xiao-Yue, Hu Xue-Chun, Chen Wei, Yu Xue-Bin, Xia Guang-Lin. Amorphous VB₂ nanoparticles for stable hydrogen storage of 2LiBH₄-MgH₂, Rare Metals 2025, 44, 5544-5553. https://doi.org/10.1007/s12598-025-03327-6..

[50] Lang Chengguang, Yao Xiangdong. Enhancing hydrogen storage performance of magnesium-based materials: a review on nanostructuring and catalytic modification, Journal of Magnesium and Alloys 2025, 13, 510-538. https://doi.org/10.1016/j.jma.2025.01.015.

[51] Mohammed Faraj Saeid B. A., M Abdulkadir H.D. Ismail, Setiabudi. Enhanced hydrogen storage properties of MgH₂ through doping with titanium-based catalyst materials: a review and bibliometric analysis, Materials Science in Semiconductor Processing 2025, 200, 109931. https://doi.org/10.1016/j.mssp.2025.109931.

[52] Ding Zhao, Li Yuting, Yang Hang, Lu Yangfan, Tan Jun, Li Jianbo, Li Qian, Chen Yu’an, L. Shaw Leon, Pan Fusheng. Tailoring MgH₂ for hydrogen storage through nanoengineering and catalysis, Journal of Magnesium and Alloys 2022, 10, 2946-2967. https://doi.org/10.1016/j.jma. 2022.09.028.

[53] Zhang Linlin, Xiong Liang, Gao Bingyang, Shi Qingyun, Wang Ying, Han Zhiya, Zhang Zhenhua, Wang Chunli, Wang Limin, Cheng Yong. Tuning microstructures of Mg-Ce-Ni hydrogen storage alloys via Cu and carbon nanotube additions, Nano Research 2024, 17, 7203-7211. https://doi.org/10.1007/s12274-024-6713-y.

[54] Chen Shuling, Jiang Wenbin, Liu Mili, Shen Shaoyang, Jiang Lin, Wang Hui, Ouyang Liuzhang. Fe-doping strategy enhances reversible hydrogen capacity and cycle stability of V-Ti-Cr solid solution alloy, Journal of Alloys and Compounds 2025, 1045, 184362. https://doi.org/10.1016/ j.jallcom.2025.184362.

[55] Yuan Zhenluo, Zhang Xiuxiu, Wu Yitian, Guan Shuyan, Zhao Shiqian, Ji Liqiang, Peng Qiuming, Han Shumin, Fan Yanping, Liu Baozhong. Effectively enhanced catalytic effect of sulfur doped Ti₃C₂ on the kinetics and cyclic stability of hydrogen storage in MgH₂, Journal of Magnesium and Alloys 2025, 13, 1843-1853. https://doi.org/10.1016/j.jma.2024.06. 016.

[56] Wu Yitian, Yuan Zhenluo, Zhang Yaojie, Peng Qiuming, Han Shumin, Fan Yanping, Liu Baozhong. Unleashing superior hydrogen storage of magnesium hydride via vanadium-doped bimetallic MXene, Inorganic Chemistry 2025, 64, 7607-7618. https://doi.org/10.1021/acs.inorgchem.5c00604.

[57] Zhao Yingyan, Zhu Yunfeng, Shi Rui, Jia Zhen, Zhang Jiguang, Liu Yana, Cheng Honghui, Tang Qinke, Ba Zhixin, Hu Xiaohui, Li Liquan. Structural inhomogeneity: a potential strategy to improve the hydrogen storage performance of metal hydrides, Journal of Materials Chemistry A 2023, 11, 13255-13265. https://doi.org/10.1039/D3TA02114A.

[58] Xiao Li-Rong, Chen Chen, Wang Shuo, Dai Zi-Yin, Kimura Hideo, Ni Cui, Hou Chuan-Xin, Sun Xue-Qin, Guo Si-Jie, Du Wei, Xie Xiu-Bo. Effects of Ti- and Nb-based transition element from single to multiple compound oxides and carbon-based composite additives on Mg-MgH₂ hydrogen storage material, Tungsten 2025, 7, 32-49. https://doi.org/10.1007/ s42864-024-00287-9.

[59] Li Can, Cheng Fujian, Liu Meijia, Long Zhi, Zhang Jiwei, Zhang Suhai, Ma Yujia, Zhang Tengyu, Kong Fangong, Novel. magnéli phase Ti₄O₇ with multi-valent titanium: superior catalytic mechanism on MgH₂ with enhanced hydrogen absorption/desorption, Chemical Engineering Journal 2025, 519, 165648. https://doi.org/10.1016/j.cej.2025. 165648.

[60] Zhu Shi-Cheng, Xiao Fang-Xing. Transition metal chalcogenides quantum dots: emerging building blocks toward solar-to-hydrogen conversion, ACS Catalysis 2023, 13, 7269-7309. https://doi.org/10.1021/acscatal.2c05401.

[61] Zhou Yu, Wang Weikang, Li Jinhe, Ren Wei, Wang Lele, Liu Qinqin. Transition metal sulfide cocatalysts: applications and challenges in photocatalytic hydrogen production, Chemical Research in Chinese Universities 2025, 41, 687-703. https://doi.org/10.1007/s40242-025-5103-z.

[62] Na Shengnan, Shi Xugen, Chai Dong-Feng, Guo Dongxuan, Li Jinlong. Synergistic hybridization between third-period and fifth-period transition metal orbitals in entropy-stabilized layered double hydroxides for long-term oxygen evolution catalysis, Journal of Colloid and Interface Science 2025, 693, 137641. https://doi.org/10.1016/j.jcis.2025.137641.

[63] Pu Chen, Wu Suqin, Deng Daijie, He Ren, Cabot Andreu, Xu Li, Li Henan, Yan Cheng. Transition metal alloy-based catalysts for zinc-air batteries: a comprehensive review, Coordination Chemistry Reviews 2026, 546, 217045. https://doi.org/10.1016/j.ccr.2025.217045.

[64] Luo Qun, Li Jianding, Li Bo, Liu Bin, Shao Huaiyu, Li Qian. Kinetics in Mg-based hydrogen storage materials: enhancement and mechanism, Journal of Magnesium and Alloys 2019, 7, 58-71. https://doi.org/10.1016/j.jma.2018.12.001.

[65] Ren Zhuanghe, Zhang Xin, Li Hai-Wen, Huang Zhenguo, Hu Jianjiang, Gao Mingxia, Pan Hongge, Liu Yongfeng.Titanium hydride nanoplates enable 5 wt% of reversible hydrogen storage by sodium alanate below 80°C, Research 2021. https://doi.org/10.34133/2021/9819176.

[66] Cao Shusheng, Li Yinghui, Wang Bolun, Rao Wentao, Wang Yanyue, Du Hao, Wang Dong, Zhang Jiaqi, Lin Xi, Zou Jianxin.Low temperature thermolysis and hydrolysis of MgH₂ generated from a titanium-mediated hydrogenation of Mg₂Si, Journal of Magnesium and Alloys 2025. https://doi.org/10.1016/j.jma.2025.07.002.

[67] Zhou Xiang, Li Jianbo, Guan Haotian, Liu Jiang, Lu Heng, Zhao Yingxiang, Chen Yu’an, Wang Jingfeng, Li Qian, Lu Yangfan, Pan Fusheng. Enhanced de/hydrogenation kinetics and cycle stability of Mg/MgH₂ by the MnO_x-coated Ti₂CT_x catalyst with optimized Ti-H bond stability, Journal of Physical Chemistry Letters 2024, 15, 8773-8780. https://doi.org/10.1021/acs.jpclett.4c01835.

[68] S.N. Madhu Yadav. Dolia, Chhagan Lal. Optimizing hydrogen storage properties: MXene (MX)-VCl₃ assisted kinetics in magnesium/magnesium hydride for sustainable energy, Journal of the Indian Chemical Society 2025, 102, 101878. https://doi.org/10.1016/j.jics.2025.101878.

[69] Ma Zhongliang, Tang Qinke, Ni Jinlian, Zhu Yunfeng, Zhang Yao, Li Hai-Wen, Zhang Jiguang, Liu Yana, Ba Zhixin, Li Liquan. Synergistic effect of TiH₂ and air exposure on enhancing hydrogen storage performance of Mg₂NiH₄, Chemical Engineering Journal 2022, 433, 134489. https://doi.org/10.1016/j.cej.2021.134489.

[70] Dong Yanfeng, Wu Zhong-Shuai, Zheng Shuanghao, Wang Xiaohui, Qin Jieqiong, Wang Sen, Shi Xiaoyu, Bao Xinhe. Ti₃C₂ MXene-derived sodium/potassium titanate nanoribbons for high-performance sodium/potassium ion batteries with enhanced capacities, ACS Nano 2017, 11, 4792-4800. https://doi.org/10.1021/acsnano.7b01165.

[71] Zhou Chengshang, Zhang Jingxi, C Robert, Jr. Bowman, Zak Fang Zhigang. Roles of Ti-based catalysts on magnesium hydride and its hydrogen storage properties, Inorganics 2021, 9, 36. https://doi.org/10.3390/inorganics9050036.

[72] Zhang Meng, Xiao Xuezhang, Wang Xinwei, Chen Man, Lu Yunhao, Liu Meijia, Chen Lixin. Excellent catalysis of TiO₂ nanosheets with high-surface-energy {001} facets on the hydrogen storage properties of MgH₂, Nanoscale 2019, 11, 7465-7473. https://doi.org/10.1039/C8NR10275A.

[73] Huang Jimei, Meng Ruijin, Zu Lianhai, Wang Zhijun, Feng Nan, Yang Ziyi, Yu Yan, Yang Jinhu. Sandwich-like Na_{0. 23}TiO₂ nanobelt/Ti₃C₂ MXene composites from a scalable in situ transformation reaction for long-life high-rate lithium/sodium-ion batteries, Nano Energy 2018, 46, 20-28. https://doi.org/10.1016/j.nanoen.2018.01.030.

[74] Wu Xin-xing, Hu Wei. First-principles study of Pd single-atom catalysis to hydrogen desorption reactions on MgH₂(110) surface, Chinese Journal of Chemical Physics 2019, 32, 319-326. https://doi.org/10.1063/1674-0068/cjcp1809209.

[75] Wang Chenlu, Hou Xiaojiang, Liu Hu, Sun Dongfeng, Li Fuping, Ge Yu, Zhao Duode, Li Danting, Xie Xinlei, Zhu Peixuan, Ye Xiaohui, Suo Guoquan, Yang Guang, Yang Yanling. Catalytic modifications to enhance the hydrogen storage behavior of Mg-based materials: single-component, multi-component single-phase and multiphase interfacial composite catalytic, Journal of Energy Chemistry 2025, 110, 393-426. https://doi.org/10.1016/j.jechem.2025.06.071.

[76] Li Yinghui, Zhang Qiuyu, Ren Li, Li Zi, Lin Xi, Ma Zhewen, Yang Haiyan, Hu Zhigang, Zou Jianxin. Core-shell nanostructured magnesium-based hydrogen storage materials: a critical review, Industrial Chemistry & Materials 2023, 1, 282-298. https://doi.org/10.1039/D3IM00061C.

[77] Chen Kang, Lau Mei Yi, Luo Xinyuan, Huang Jiani, Ouyang Liuzhang, Yang Xu-Sheng. Research progress in solid-state hydrogen storage alloys: a review, Journal of Materials Science and Technology 2026, 246, 256-289. https://doi.org/10.1016/j.jmst.2025.05.037.

[78] Wang Hongyuan, Li Jie, Wei Xinlin, Zheng Yan, Yang Shenglan, Lu Yangfan, Ding Zhao, Luo Qun, Li Qian, Pan Fusheng. Thermodynamic and kinetic regulation for Mg-based hydrogen storage materials: challenges, strategies, and perspectives, Advanced Functional Materials 2024, 34, 2406639. https://doi.org/10.1002/adfm.202406639.

[79] Yang Lin, Zeng Wen, Li Yanqiong. Advancements in the modification of magnesium-based hydrogen storage materials, Progress in Natural Science: Materials International 2024, 34, 540-554. https://doi.org/10.1016/j.pnsc.2024.05.001.

[80] Lu Heng, Li Jianbo, Zhang Ruilin, Nie Kunyan, Li Qian, Chen Yu’an, Pan Fusheng. Advances and perspectives of two-dimensional materials MXenes: efficient catalysts for magnesium hydride, Renewable and Sustainable Energy Reviews 2025, 217, 115759. https://doi.org/10.1016/j.rser.2025.115759.

[81] Jia Kai, Wu Yake, Wang Xiuzhen, Wu Fuying, Shang Danhong, Li Hong, Zhang Liuting. A review on 2LiBH₄-MgH₂ reactive hydride composite for hydrogen storage: performance optimization and perspectives, Journal of Energy Storage 2025, 134, 118160. https://doi.org/10.1016/j.est.2025.118160.

[82] Hirose Takashi, Matsui Naoki, Itoh Takashi, Hinuma Yoyo, Ikeda Kazutaka, Gotoh Kazuma, Jiang Guangzhong, Suzuki Kota, Hirayama Masaaki, Kanno Ryoji. High-capacity, reversible hydrogen storage using H^--conducting solid electrolytes, Science 2025, 389, 1252-1255. https://doi.org/10.1126/science.adw1996.

[83] Li Chaoqun, Ding Ying, Zhang Xiaoyue, Hu Xuechun, Yu Xuebin, Sun Dalin, Xia Guanglin. Hydrogen storage in magnesium hydride at room temperature enabled by graphene-stabilized multivalent niobium oxides, Advanced Materials 2025, 37, e11759. https://doi.org/10.1002/adma.202511759.

[84] Duan Xingqing, Liang Shuo, He Shixuan, Chen Jinting, Zhang Zeyu, Liu Bogu, Li Yawei, Huang Haixiang, Wu Ying. Mechanistic insights into the enhancement of MgH₂ hydrogen storage performance by ultra-stable bimetallic Mo₂V₂C₃ MXene, Journal of Energy Chemistry 2025, 108, 724-735. https://doi.org/10.1016/j.jechem.2025.05.020.

[85] Shao Longfei, Lin Xi, Bian Liansen, Wang Yanyue, Hu Shouyi, Han Yaobin, Huang Ke, Zhang Ning, Zhang Jiaqi, Zou Jianxin. Engineering control strategy of hydrogen gas direct-heating type Mg-based solid state hydrogen storage tanks: A simulation investigation, Applied Energy 2024, 375, 124134. https://doi.org/10.1016/j.apenergy.2024.124134.

[86] Ma Zhenxuan, Zheng Jiaguang, Xia Ao, Zhang Qingbo, Lv Meiling, Li Cong, Zhou Panpan. Enhanced hydrogen storage performance of Mg(BH₄)₂ with in-situ generated TiO₂ and TiH₂ catalysts, Chemical Engineering Journal 2025, 512, 162488. https://doi.org/10.1016/j.cej.2025.162488.

[87] Liu Shiyuan, Zhang Yue, Zhu Fangzhou, Liu Jieyuan, Wan Xin, Liu Ruonan, Liu Xiaofang, Shang Jia-Xiang, Yu Ronghai, Feng Qiang, Wang Zili, Shui Jianglan. Mg-MOF-74 derived defective framework for hydrogen storage at above-ambient temperature assisted by Pt catalyst, Advanced Science 2024, 11, 2401868. https://doi.org/10.1002/advs.202401868.

[88] Zhang Xin, Liu Yongfeng, Wang Ke, Gao Mingxia, Pan Hongge. Remarkably improved hydrogen storage properties of nanocrystalline TiO₂-modified NaAlH₄ and evolution of Ti-containing species during dehydrogenation/hydrogenation, Nano Research 2015, 8, 533-545. https://doi.org/10.1007/s12274-014-0667-9.

[89] Yuan Zhenluo, Zhang Dafeng, Fan Guangxin, Chen Yumei, Fan Yanping, Liu Baozhong. Synergistic effect of CeF₃ nanoparticles supported on Ti₃C₂ MXene for catalyzing hydrogen storage of NaAlH₄, ACS Applied Energy Materials 2021, 4, 2820-2827. https://doi.org/10.1021/acsaem.1c00122.

[90] Zhang Huanhuan, Kong Qianqian, Hu Song, Zhang Dafeng, Chen Haipeng, Xu Chunbao Charles, Li Baojun, Fan Yanping, Liu Baozhong. Engineering the oxygen vacancies in Na₂Ti₃O₇ for boosting its catalytic performance in MgH₂ hydrogen storage, ACS Sustainable Chemistry&Engineering 2021, 10, 363-371. https://doi.org/10.1021/acssuschemeng.1c06444.

[91] Zhu Jiajing, Wang Hui, Zhai Yuqi, Huang Liangjun, Cui Jie, Ouyang Liuzhang, Zhu Min, Huot Jacques. Cr-doped TiO₂ catalyzing fast hydrogen absorption of MgH₂ at subzero temperatures, ACS Applied Energy Materials 2024, 7, 6667-6676. https://doi.org/10.1021/acsaem.4c01283.

[92] Wang Yuhang, Fan Guangxin, Zhang Dafeng, Fan Yanping, Liu Baozhong. Striking enhanced effect of PrF₃ particles on Ti₃C₂ MXene for hydrogen storage properties of MgH₂, Journal of Alloys and Compounds 2022, 914, 165291. https://doi.org/10.1016/j.jallcom.2022.165291.

[93] Ren Li. Oxygen vacancy-rich 2D TiO₂ nanosheets: a bridge toward high stability and rapid hydrogen storage kinetics of nano-confined MgH₂, Nano-Micro Letters 2022, 14, 144. https://doi.org/10.1007/s40820-022-00891-9.

[94] Jain Ankur, Agarwal Shivani, Kumar Sanjay, Yamaguchi Shotaro, Miyaoka Hiroki, Kojima Yoshitsugu, Ichikawa Takayuki. How does TiF₄ affect the decomposition of MgH₂ and its complex variants? -An XPS investigation, Journal of Materials Chemistry A 2017, 5, 15543-15551. https://doi.org/10.1039/C7TA03081A.

[95] Chen Man, Xiao Xuezhang, Zhang Meng, Liu Meijia, Huang Xu, Zheng Jiaguang, Zhang Yiwen, Jiang Lijun, Chen Lixin. Excellent synergistic catalytic mechanism of in-situ formed nanosized Mg₂Ni and multiple valence titanium for improved hydrogen desorption properties of magnesium hydride, International Journal of Hydrogen Energy 2019, 44, 1750-1759. https://doi.org/10.1016/j.ijhydene.2018.11.118.

[96] Zhang Meng, Xiao Xuezhang, Luo Bosang, Liu Meijia, Chen Man, Chen Lixin. Superior de/hydrogenation performances of MgH₂ catalyzed by 3D flower-like TiO₂@C nanostructures, Journal of Energy Chemistry 2020, 46, 191-198. https://doi.org/10.1016/j.jechem.2019.11.010.

[97] Gao Haiguang, Shi Rui, Shao Yuting, Liu Yana, Zhu Yunfeng, Zhang Jiguang, Hu Xiaohui, Li Liquan, Ba Zhixin. One-step self-assembly of TiO₂/MXene heterostructures for improving the hydrogen storage performance of magnesium hydride, Journal of Alloys and Compounds 2022, 895, 162635. https://doi.org/10.1016/j.jallcom.2021.162635.

[98] Gao Haiguang, Shi Rui, Zhu Jinglian, Liu Yana, Shao Yuting, Zhu Yunfeng, Zhang Jiguang, Li Liquan, Hu Xiaohui. Interface effect in sandwich like Ni/Ti₃C₂ catalysts on hydrogen storage performance of MgH₂, Applied Surface Science 2021, 564, 150302. https://doi.org/10.1016/j.apsusc.2021.150302

[99] Huang Xu, Xiao Xuezhang, Wang Xuancheng, Wang Chuntao, Fan Xiulin, Tang Zhichu, Wang Caiyun, Wang Qidong, Chen Lixin. Synergistic catalytic activity of porous rod-like TMTiO₃ (TM = Ni and Co) for reversible hydrogen storage of magnesium hydride, The Journal of Physical Chemistry C 2018, 122, 27973-27982. https://doi.org/10.1021/acs.jpcc.8b10387.

[100] Zhang Meng, Xiao Xuezhang, Hang Zhouming, Chen Man, Wang Xuancheng, Zhang Nan, Chen Lixin. Superior catalysis of NbN nanoparticles with intrinsic multiple valence on reversible hydrogen storage properties of magnesium hydride, International Journal of Hydrogen Energy 2021, 46, 814-822. https://doi.org/10.1016/j.ijhydene.2020.09.173.

[101] Huang Tianping, Huang Xu, Hu Chuanzhu, Wang Jie, Liu Huabing, Xu Hao, Sun Fengzhan, Ma Zhewen, Zou Jianxin, Ding Wenjiang. MOF-derived Ni nanoparticles dispersed on monolayer MXene as catalyst for improved hydrogen storage kinetics of MgH, Chemical Engineering Journal 2021, 421, 127851. https://doi.org/10.1016/j.cej.2020.127851.

[102] Lu Chong, Ma Yanling, Li Fan, Zhu Hong, Zeng Xiaoqin, Ding Wenjiang, Deng Tao, Wu Jianbo, Zou Jianxin. Visualization of fast “hydrogen pump” in core-shell nanostructured Mg@Pt through hydrogen-stabilized Mg₃Pt, Journal of Materials Chemistry A 2019, 7, 14629-14637. https://doi.org/10.1039/C9TA03038G.

[103] Wu Yali, Meng Yuqin, Ma Li, Zhao Junmiao, Tang Jianling, Chen Hongshan. How does Ti-doping affect hydrogen storage properties of MgH₂ at nanosize? Russian Journal of Physical Chemistry A 2021, 95, 1424-1431. https://doi.org/10.1134/S0036024421070293.

[104] Chen Man, Xiao Xuezhang, Zhang Meng, Zheng Jiaguang, Liu Meijia, Wang Xuancheng, Jiang Lijun, Chen Lixin. Highly dispersed metal nanoparticles on TiO₂ acted as nano redox reactor and its synergistic catalysis on the hydrogen storage properties of magnesium hydride, International Journal of Hydrogen Energy 2019, 44, 15100-15109. https://doi.org/10.1016/j.ijhydene.2019.04.047.

[105] Wang Qingqing, Kong Xianggang, Han Huilei, Sang Ge, Zhang Guanghui, Gao Tao. The performance of adsorption, dissociation and diffusion mechanism of hydrogen on the Ti-doped ZrCo(110) surface, Physical Chemistry Chemical Physics 2019, 21, 12597-12605. https://doi.org/10.1039/C9CP02491C.

[106] Gong Xu, Shao Xiaohong, Stability. electronic structure, and dehydrogenation properties of pristine and doped 2D MgH₂ by the first principles study, Metals 2018, 8, 482. https://doi.org/10.3390/met8070482.

[107] Erkisi Aytac, Gökoglu Gökhan. First principles investigation of Mg₇XH₁₆ (X = Ti, Zn, Pd, and Cd) ternary hydrides for hydrogen storage applications, Materials Research Express 2018, 5, 065517. https://doi.org/10.1088/2053-1591/aacbb6.

[108] Wang Lei, Zhao Baozhou, Liu Jiangchuan, Yuan Jianguang, Zhu Yunfeng, Liu Bogu, Wu Ying, Li Liquan.Yong Cheng, S. X. Zhou. Effect of Ti-EG-Ni dual-metal organic crystal-derived TiO₂/C/Ni on the hydrogen storage performance of MgH₂, ACS Applied Materials & Interfaces 2025, 17, 15274-15286. https://doi.org/10.1021/acsami.4c18239.

[109] Wang Zhao-Yi. Role of metal impurity in hydrogen diffusion from surface into bulk magnesium: a theoretical study, Physics Letters A 2017, 381, 3696-3700. https://doi.org/10.1016/j.physleta.2017.09.035.

[110] Dai J.H., Jiang X.W., Song Y.. Stability and hydrogen adsorption properties of Mg/TiMn₂ interface by first principles calculation, Surface Science 2016, 653, 22-26. https://doi.org/10.1016/j.susc.2016.05.006.

[111] Huang Zhuonan, Wang Yuqi, Zhang Meiguang. Excellent catalytic activity of two-dimensional Ti₂C and Ti₂CT₂ (T = O, F, OH) monolayers on hydrogen storage of MgH₂: first-principles calculations, International Journal of Hydrogen Energy 2021, 46 (66), 33176-33185. https://doi.org/10.1016/j.ijhydene.2021.07.168.

[112] Pan Yong, Chen Shuang. Exploring the novel structure, transportable capacity and thermodynamic properties of TiH₂ hydrogen storage material, International Journal of Energy Research 2020, 44, 11. https://doi.org/10.1002/er.5260.

[113] Mohammed Faraj Saeid B. A., M Abdulkadir H.D. Ismail, Setiabudi. Hydrogen storage in MgH₂ catalyzed by Fe nanoparticles and hollow silica spheres, Fuel 2025, 400, 135635. https://doi.org/10.1016/j.fuel.2025.135635.

[114] Hu Chunyan, Mo Xiaohua, Zhou Haojie, Li Xiulan, Zuo Xiaoli, Ma Yu, Jiang Weiqing. Insight into enhanced dehydrogenation of LiBH₄ modified by Ti and O from first-principles calculations, Computational & Theoretical Chemistry 2024, 1238, 114718. https://doi.org/10.1016/j.comptc.2024.114718.

[115] Yang Huimin, Sun Xuan, Luo Qun, Lu Yangfan, Li Qian, Pan Fusheng. Superior hydrogen storage kinetics of MgH₂ by in-situ generated α-Fe from the Fe-zeolitic imidazolate framework, Scripta Materialia 2024, 239, 115782. https://doi.org/10.1016/j.scriptamat.2023.115782.

[116] Han Bo,Jia Yuxiao, Wang Jianchuan, Xiao Xuezhang, Chen Lixin, Sun Lixian, Du Yong, structural The. energetic and dehydrogenation properties of pure and Ti-doped Mg(0001)/MgH₂(110) interfaces, Journal of Materials Chemistry A 2023, 11, 26602-26616. https://doi.org/10.1039/D3TA06177A.

[117] Zhang J., Sun L.Q., P Y.C. Zhou,. Peng Dehydrogenation thermodynamics of magnesium hydride doped with transition metals: Experimental and theoretical studies, Computational Materials Science 2015, 98, 211-219. https://doi.org/10.1016/j.commatsci.2014.11.016.

[118] Ren Kaixiang, Ding Xiaoli, Cheng Yuwen, Li Hai-Wen, Li Yongtao. in situ hydrogenolysis-engineered Ti_xC MXenes synergistically enhance hydrogen storage in magnesium, Journal of Colloid and Interface Science 2025, 699, 138204. https://doi.org/10.1016/j.jcis.2025.138204.

[119] Wang Ying, Li Li, An Cuihua, Wang Yijing, Chen Chengcheng, Jiao Lifang, Yuan Huatang. Facile synthesis of TiN decorated graphene and its enhanced catalytic effects on dehydrogenation performance of magnesium hydride, Nanoscale 2014, 6, 6684-6691. https://doi.org/10.1039/C4NR00474D.

[120] Baran Agata, R Torben, Jensen, Polański Marek. High-temperature high-pressure reactive ball milling synthesis of Mg-Ni-based solid-state hydrogen storage materials, Journal of Energy Storage 2024, 103, 114271. https://doi.org/10.1016/j.est.2024.114271.

[121] Zhang Rui-Lin, Li Jian-Bo, Lu Heng, Nie Kun-Yan, Li Hong-Yi, Zhang Er-Ni, Qiang Zhen-Hui, Liu Bo-Yu, Chen Yu-An, Pan Fu-Sheng. Synergistic enhancement of hydrogen storage thermodynamic and kinetic performances in Mg-La-Ce alloys via Ti particle doping, Rare Metals 2025. https://doi.org/10.1007/s12598-025-03580-9.

[122] Xu Yaohui, Li Yuting, Hou Quanhui, Hao Yechen, Ding Zhao. Ball milling innovations advance Mg-based hydrogen storage materials towards practical applications, Materials 2024, 17, 2510. https://doi.org/10.3390/ma17112510.

[123] El-Eskandarany M. Sherif. Superior catalytic effect of nanocrystalline big-cube Zr₂Ni metastable phase for improving the hydrogen sorption/desorption kinetics and cyclability of MgH₂ powders, Energy 2015, 91, 274-282. https://doi.org/10.1016/j.energy.2015.07.135.

[124] Hong Haoliang R.P. Alexander, Harrison, Nie Binjian. Linking the microstructure of ball-milled Mg-Ni hydrogen storage materials to reactive properties and techno-economic feasibility, Energy & Fuels 2025, 39, 13789-13800. https://doi.org/10.1021/acs.energyfuels.5c01986.

[125] Viktor N. Kudiyarov R. Elman Roman. Nikita E. Kurdyumov. The effect of high-energy ball milling conditions on microstructure and hydrogen desorption properties of magnesium hydride and single-walled carbon nanotubes, Metals 2021, 11, 1409. https://doi.org/10.3390/met11091409.

[126] Gao Ge, Xie Jia-Xing, Zhang Liu-Ting, Lv Chun-Ju, Li Chao, Fan Mei-Qiang, Yao Zhen-Dong. Improvement on hydrogen storage performance of MgH₂ by THF-promoted nano-crystallization under low-speed ball milling, Rare Metals 2025, 44, 6366-6374. https://doi.org/10.1007/s12598-025-03330-x.

[127] Huang Yike, An Cuihua, Zhang Qiuyu, Zang Lei, Shao Huaxu, Liu Yafei, Zhang Yan, Yuan Huatang, Wang Caiyun, Wang Yijing. Cost-effective mechanochemical synthesis of highly dispersed supported transition metal catalysts for hydrogen storage, Nano Energy 2021, 80, 105535. https://doi.org/10.1016/j.nanoen.2020.105535.

[128] Hou Xiaojiang, Zhao Duode, Cao Qianhong, Wang Chenlu, Li Danting, Xie Xinlei, Zhu Peixuan, Ye Xiaohui, Suo Guoquan, Yang Guang, Yang Yanling. Optimizing Ti₃C₂T_x to activate passivated Mg for direct and widespread application in hydrogen storage, Renewable Energy 2026, 256, 124302. https://doi.org/10.1016/j.renene.2025.124302.

[129] Jiang Yi, Si Nan, Wang Zan, Zhang Hui, Jiang Wei. Improved hydrogen storage kinetic properties of MgH₂ with NiO/NiCo(Fe)₂O₄/(Ni), Energy & Fuels 2024, 38, 23804-23814. https://doi.org/10.1021/acs.energyfuels.4c04640.

[130] Nurmalita Malahayati. Ismail M. N. Machmud Z. Jalil. Sorption behavior of MgH₂-Ti for Hydrogen storage material prepared by high pressure milling, Journal of Physics: Conference Series 2021, 1882, 012005. https://doi.org/10.1088/1742-6596/1882/1/012005.

[131] Sun Lei, Sun Rong, Liu Jianjun, Zhu Mengzhou, Zhang Xiaoqin, Guo Dongliang, Yin Kangyong, Zhuang Zhiyun, Zhu Xueqiong, Xiao Peng. Coupling of two-dimensional MXenes and graphene for boosting the hydrogen storage performance of MgH₂, Nanoscale 2024, 16, 19873-19880. https://doi.org/10.1039/D4NR02868F.

[132] Zhang Guorong, Liang Taigen, Xu Fen, Sun Lixian, Wei Sheng, Liu Jiaxi, Qin Lina, Lin Xia, Xia Yongpeng.Structural and defect engineering of Pt-loaded MAX fibers with oxygen vacancies for enhanced hydrogen storage properties of MgH₂, Journal of Magnesium and Alloys 2025. https://doi.org/10.1016/j.jma.2025.08.024.

[133] Yuan Zhenluo, Wang Yuhang, Zhang Xiuxiu, Guan Shuyan, Wang Xiaojiao, Ji Liqiang, Peng Qiuming, Han Shumin, Fan Yanping, Liu Baozhong. Catalytic effects of V- and O-species derived from PrF₃/V₂C for efficient hydrogen storage in MgH₂, Nano Research 2024, 17, 7117-7125. https://doi.org/10.1007/s12274-024-6550-4.

[134] Yan Nianhua, Lu Xiong, Lu Zhiyu, Yu Haijie, Wu Fuying, Zheng Jiaguang, Wang Xiuzhen, Zhang Liuting. Enhanced hydrogen storage properties of Mg by the synergistic effect of grain refinement and NiTiO₃ nanoparticles, Journal of Magnesium and Alloys 2022, 10, 3542-3552. https://doi.org/10.1016/j.jma.2021.03.014.

[135] Lu Xiong. Achieving superior hydrogen storage properties of MgH₂ by the effect of TiFe and carbon nanotubes, Chemical Engineering Journal 2021, 422, 130101. https://doi.org/10.1016/j.cej.2021.130101.

[136] Zhang Yanghuan, Wei Xin, Zhang Wei, Yuan Zeming, Gao Jinliang, Ren Huiping. Catalytic effect comparison of TiO₂ and La₂O₃ on hydrogen storage thermodynamics and kinetics of the as-milled La-Sm-Mg-Ni-based alloy, Journal of Magnesium and Alloys 2021, 9, 2063-2077. https://doi.org/10.1016/j.jma.2021.03.006.

[137] Lu Zhi-Yu. Two-dimensional vanadium nanosheets as a remarkably effective catalyst for hydrogen storage in MgH₂, Rare Met. 2021, 40, 10. https://doi.org/10.1007/s12598-021-01764-7.

[138] Xu Nuo, Wang Kaiwen, Zhu Yunfeng, Zhang Yao. PdNi biatomic clusters from metallene unlock record‐low onset dehydrogenation temperature for bulk‐MgH₂, Advanced Materials 2023, 35 (38), 2303173. https://doi.org/10.1002/adma.202303173.

[139] Peng Cong, Yang Cuizhen, Zhang Qingan. Few-layer MXene Ti₃C₂T_x supported Ni@C nanoflakes as a catalyst for hydrogen desorption of MgH₂, Journal of Materials Chemistry A 2022, 10, 12409-12417. https://doi.org/10.1039/D2TA02958H.

[140] Wang Zexuan, Tian Zhihui, Yao Pufan, Zhao Huimin, Xia Chaoqun, Yang Tai. Improved hydrogen storage kinetic properties of magnesium-based materials by adding Ni₂P, Renewable Energy 2022, 189, 559-569. https://doi.org/10.1016/j.renene.2022.03.001.

[141] Xu Yaohui, Zhou Yang, Li Yuting, Hao Yechen, Wu Pingkeng, Ding Zhao. Recent advances in the preparation methods of magnesium-based hydrogen storage materials, Molecules 2024, 29, 2451. https://doi.org/10.3390/molecules 29112451.

[142] S Sumanth Dongre, R Shwetharani. Chandan Hunsur Ravikumar, Lavanya C, R. Geetha Balakrishna. Review on 2D arsenene and antimonene: emerging materials for energy, electronic and biological applications, Advanced Materials Interfaces 2022, 9, 2200442. https://doi.org/10.1002/admi.202200442.

[143] Ouyang Liuzhang, Cao Zhijie, Wang Hui, Hu Renzhong, Zhu Min. Application of dielectric barrier discharge plasma-assisted milling in energy storage materials-A review, Journal of Alloys and Compounds 2017, 691, 422-435. https://doi.org/10.1016/j.jallcom.2016.08.179.

[144] Ouyang L.Z., Cao Z.J., Wang H., Liu J.W., Sun D.L., Zhang Q.A., Zhu M.. Enhanced dehydriding thermodynamics and kinetics in Mg(In)-MgF₂ composite directly synthesized by plasma milling, Journal of Alloys and Compounds 2014, 586, 113-117. https://doi.org/10.1016/j.jallcom.2013.10.029.

[145] Wang Hui, Zeng Meiqin, Liu Jiangwen, Lu Zhongcheng, Shi Zhenhua, Ouyang Liuzhang, Zhu Min. One-step synthesis of ultrafine WC-10Co hardmetals with VC/V₂O₅ addition by plasma assisted milling, International Journal of Refractory Metals and Hard Materials 2015, 48, 97-101. https://doi.org/10.1016/j.ijrmhm.2014.07.035.

[146] Cao Zhijie, Ouyang Liuzhang, Wu Yuyu, Wang Hui, Liu Jiangwen, Fang Fang, Sun Dalin, Zhang Qingan, Zhu Min. Dual-tuning effects of In, Al, and Ti on the thermodynamics and kinetics of Mg₈₅In₅Al₅Ti₅ alloy synthesized by plasma milling, Journal of Alloys and Compounds 2015, 623, 354-358. https://doi.org/10.1016/j.jallcom.2014.10.200.

[147] Yang Bo, Zou Jianxin, Huang Tianping, Mao Jianfeng, Zeng Xiaoqin, Ding Wenjiang. Enhanced hydrogenation and hydrolysis properties of core-shell structured Mg-MO_x (M = Al, Ti and Fe) nanocomposites prepared by arc plasma method, Chemical Engineering Journal 2019, 371, 233-243. https://doi.org/10.1016/j.cej.2019.04.046.

[148] Zhang Xin,Liu Yongfeng, Ren Zhuanghe, Zhang Xuelian, Hu Jianjiang, Huang Zhenguo, Lu Yunhao, Gao Mingxia, Pan Hongge. Realizing 6. 7 wt% reversible storage of hydrogen at ambient temperature with non-confined ultrafine magnesium hydrides, Energy & Environmental Science 2021, 14, 2302-2313. https://doi.org/10.1039/D0EE03160G.

[149] Chen Shenghua, Zheng Xiaobo, Zhu Peng, Li Yapeng, Zhuang Zechao, Wu Hangjuan, Zhu Jiexin, Xiao Chunhui, Chen Mingzhao, Wang Pingshan, Wang Dingsheng, He Ya-Ling. Copper atom pairs stabilize *OCCO dipole toward highly selective CO₂ electroreduction to C₂H₄, Angewandte Chemie International Edition 2024, 63, e202411591. https://doi.org/10.1002/anie.202411591.

[150] Zhao Zeyu, Chen Ting, Ding Bing, Zhang Shengliang, Chen Duo, Chen Gao, Zhu Yanping, Zhang Xiaogang. Reaction route innovates design of metal supported single atom electrocatalysts for hydrogen evolution: a review, Chemical Engineering Journal 2025, 523, 168834. https://doi.org/10.1016/j.cej.2025.168834.

[151] Guan Shuyan, Yuan Zhenluo, Zhao Shiqian, Zhuang Zechao, Zhang Huanhuan, Shen Ruofan, Fan Yanping, Li Baojun, Wang Dingsheng, Liu Baozhong. Efficient hydrogen generation from ammonia borane hydrolysis on a tandem ruthenium-platinum-titanium catalyst, Angewandte Chemie International Edition 2024, 63, e202408193. https://doi.org/10.1002/anie.202408193.

[152] Ye Bo-Chao, Li Wen-Hao, Zhang Xia, Chen Jian, Gao Yong, Wang Dingsheng, Pan Hongge. Advancing heterogeneous organic synthesis with coordination chemistry-empowered single-atom catalysts, Advanced Materials 2024, 36, 2402747. https://doi.org/10.1002/adma.202402747.

[153] Wang Xin-Yu, Wei Wan-Jie, Zhou Si-Yu, Pan Yong-Zhou, Yang Jiarui, Gan Tao, Zhuang Zechao, Li Wen-Hao, Zhang Xia, Pan Ying-Ming, Tang Hai-Tao, Wang Dingsheng. Phosphorus-doped single atom copper catalyst as a redox mediator in the cathodic reduction of quinazolinones, Angewandte Chemie International Edition 2025, 64, e202505085. https://doi.org/10.1002/anie.202505085.

[154] Yu Luo, Ning Minghui, Wang Yu, Yuan Chuqing, Ren Zhifeng. Direct seawater electrolysis for hydrogen production, Nature Reviews Materials 2025, 10, 857-873. https://doi.org/10.1038/s41578-025-00826-x.

[155] Tang Bing, Ji Qianqian, Zhang Xilin, Shi Runchuan, Ma Jin, Zhuang Zechao, Sun Mei, Wang Huijuan, Liu Ruiqi, Liu Hengjie, Wang Chao, Guo Zhiying, Lu Lanlu, Jiang Peng, Wang Dingsheng, Yan Wensheng. Symmetry breaking of FeN₄ moiety via edge defects for acidic oxygen reduction reaction, Angewandte Chemie International Edition 2025, 64, e202424135. https://doi.org/10.1002/anie.202424135.

[156] Shen Ji, Chen Jian, Qian Yuping, Wang Xinqiang, Wang Dingsheng, Pan Hongge, Wang Yuguang. Atomic engineering of single-atom nanozymes for biomedical applications, Advanced Materials 2024, 36, 2313406. https://doi.org/10.1002/adma.202313406.

[157] Zhou Hanghang, Ye Wenqiang, Jiang Jizhou, Wang Zheng. Recent advances on surface modification of non-oxide photocatalysts towards efficient CO₂ conversion, Carbon Letters 2024, 34, 1569-1591. https://doi.org/10.1007/s42823-024-00748-8.

[158] Wang Ligang, Wang Dingsheng, Li Yadong. Single-atom catalysis for carbon neutrality, Carbon Energy 2022, 4, 1021-1079. https://doi.org/10.1002/cey2.194.

[159] Zhuang Jiahao, Wang Dingsheng. Recent advances of single-atom alloy catalyst: properties, synthetic methods and electrocatalytic applications, Materials Today Catalysis 2023, 2, 100009. https://doi.org/10.1016/j.mtcata.2023.100009.

[160] Duan Congwen, Tian Yating, Wang Xinya, Wu Jinhui, Liu Bogu, Fu Dong, Zhang Yuling, Lv Wei, Hu Lianxi, Wang Fei, Zhang Xu, Wu Ying. Anchoring Mo single atoms on N-CNTs synchronizes hydrogenation/dehydrogenation property of Mg/MgH₂, Nano Energy 2023, 113, 108536. https://doi.org/10.1016/j.nanoen.2023.108536.

[161] Huang Haixiang, Xu Tingting, Chen Jinting, Yuan Jianguang, Yang Weijie, Liu Bogu, Zhang Bao, Wu Ying. Enhanced catalysis of Pd single atoms on Sc₂O₃ nanoparticles for hydrogen storage of MgH₂, Chemical Engineering Journal 2024, 483, 149434. https://doi.org/10.1016/j.cej.2024.149434.

[162] Miao Yi, Zheng Shuzhe, Qi Jiaqi, Xiao Mingyi, Tan Mingwu, Hu Zhongting, Li Xiaonian, Tian Jinshu, Zhu Yihan. Deactivation mechanisms and mitigation strategies for nickel-based acetylene semi-hydrogenation catalysts, Catalysis Science & Technology 2025. https://doi.org/10.1039/D5CY00098J.

[163] Lang Zhiquan, Wang Xixi, Jabeen Sobia, Cheng Yuanyuan, Liu Naiyun, Liu Zhenhui, Gan Tao, Zhuang Zechao, Li Haitao, Wang Dingsheng. Destabilization of single-atom catalysts: characterization, mechanisms, and regeneration strategies, Advanced Materials 2025, 37, 2418942. https://doi.org/10.1002/adma.202418942.

[164] Sun Xuejiao, Chen Cai, Xiong Can, Zhang Congmin, Zheng Xusheng, Wang Jin, Gao Xiaoping, Yu Zhen-Qiang, Wu Yuen. Surface modification of MoS₂ nanosheets by single Ni atom for ultrasensitive dopamine detection, Nano Research 2023, 16, 917-924. https://doi.org/10.1007/s12274-022-4802-8.

[165] Bai Jirong, Lian Yuebin, Deng Yaoyao, Xiang Mei, Xu Peng, Zhou Quanfa, Tang Yawen, Su Yaqiong. Simultaneous integration of Fe clusters and NiFe dual single atoms in nitrogen-doped carbon for oxygen reduction reaction, Nano Research 2024, 17, 2291-2297. https://doi.org/10.1007/s12274-023-6038-7.

[166] Wang Xin-Yu, Pan Yong-Zhou, Yang Jiarui, Li Wen-Hao, Gan Tao, Pan Ying-Ming, Tang Hai-Tao, Wang Dingsheng. Single-atom iron catalyst as an advanced redox mediator for anodic oxidation of organic electrosynthesis, Angewandte Chemie International Edition 2024, 63, e202404295. https://doi.org/10.1002/anie.202404295.

[167] Liu Tianhao, Guo Jingyi, Wu Aiping, Shen Di, Fan Yuying, Fu Yu, Liang Zhijian, Wang Dongxu, Xie Ying, Tian Chungui. Single-atom Ru confined in self-supported mesoporous carbon films for efficient and stable acidic oxygen evolution, Chemical Engineering Journal 2025, 512, 162387. https://doi.org/10.1016/j.cej.2025.162387.

[168] Q. Mu Xueqin, L. Liu Suli, Y Mengyang, Zhang, C Zechao, Zhuang, Chen Ding, R. Liao Yuru, Y. Zhao Hongyu, C. Mu Shichun, S. Wang Dingsheng, H. Dai. Zhihui. Symmetry-broken Ru nanoparticles with parasitic Ru-Co dual-single atoms overcome the volmer step of alkaline hydrogen oxidation, Angewandte Chemie International Edition 2024, 63, e202319618. https://doi.org/10.1002/anie.202319618.

[169] Li Shuying, Zhang Gong, Ma Xiao, Gao Hui, Fu Donglong, Wang Tuo, Zeng Jianrong, Zhao Zhi-Jian, Zhang Peng, Gong Jinlong. Atomically isolated pd sites promote electrochemical CO reduction to acetate through a protonation-regulated mechanism, Journal of the American Chemical Society 2024, 146, 31927-31934. https://doi.org/10.1021/jacs.4c11276.

[170] Tang Minhao, Shen Ji, Zhang Fengtao, Zhao Yanfei, Gan Tao, Zeng Wei, Li Rongxiang, Wang Dingsheng, Han Buxing, Liu Zhimin. Upcycling of polyamide wastes to tertiary amines using Mo single atoms and Rh nanoparticles, Angewandte Chemie International Edition 2025, 64, e202416436. https://doi.org/10.1002/anie.202416436.

[171] Xia Junkai, Xu Jiawei, Yu Bing, Liang Xiao, Qiu Zhen, Li Hao, Feng Huajun, Li Yongfu, Cai Yanjiang, Wei Haiyan, Li Haitao, Xiang Hai, Zhuang Zechao, Wang Dingsheng. A metal-sulfur-carbon catalyst mimicking the two-component architecture of nitrogenase, Angewandte Chemie International Edition 2024, 63, e202412740. https://doi.org/10.1002/anie.202412740.

[172] C. Gerber Iann, Serp Philippe. A theory/experience description of support effects in carbon-supported catalysts, Chemical Reviews 2020, 120, 1250-1349. https://doi.org/10.1021/acs.chemrev.9b00209.

[173] Yang Hongcen, Lu Niandi, Zhang Juntao, Wang Rui, Tian Shuhao, Wang Mengjun, Wang Zhixia, Tao Kun, Ma Fei, Peng Shanglong. Ultra-low single-atom Pt on g-C₃N₄ for electrochemical hydrogen peroxide production, Carbon Energy 2023, 5, e337. https://doi.org/10.1002/cey2.337.

[174] Dong Shuai, Liu Hao, Liu Xinyuan, Li Chaoqun, Gao Zhengyang, Liu Bogu, Yang Weijie, Wu Ying. Facile dehydrogenation of MgH₂ enabled by γ-graphyne based single-atom catalyst, Journal of Energy Storage 2023, 74, 109484. https://doi.org/10.1016/j.est.2023.109484.

[175] Lv Liyang, Tan Hao, Kong Yuan, Tang Bing, Ji Qianqian, Liu Yuying, Wang Chao, Zhuang Zechao, Wang Huijuan, Ge Min, Fan Minghui, Wang Dingsheng, Yan Wensheng. Breaking the scaling relationship in C-N coupling via the doping effects for efficient urea electrosynthesis, Angewandte Chemie International Edition 2024, 63, e202401943. https://doi.org/10.1002/anie.202401943.

[176] Cui Xinkang, Liu Kaiwei, Han Yajing, Wang Liqiang. Rational design of single-atom catalysts for efficient hydrogenation of nitro compounds, Chemical Synthesis 2025, 5, 79. https://doi.org/10.20517/cs.2025.71.

[177] Ma Fengya, Zhang Pengfang, Zheng Xiaobo, Chen Liang, Li Yunrui, Zhuang Zechao, Fan Yameng, Jiang Peng, Zhao Hui, Zhang Jiawei, Dong Yuming, Zhu Yongfa, Wang Dingsheng, Wang Yao. Steering the site distance of atomic Cu-Cu pairs by first-shell halogen coordination boosts CO₂-to-C₂ selectivity, Angewandte Chemie International Edition 2024, 63, e202412785. https://doi.org/10.1002/anie.202412785.

[178] Dong Shuai, Li Chaoqun, Lv Erfei, Wang Jinhui, Liu Hao, Gao Zhengyang, Xiong Wei, Ding Zhao, Yang Weijie, Li Hao. MgH₂/single-atom heterojunctions: effective hydrogen storage materials with facile dehydrogenation, Journal of Materials Chemistry A 2022, 10, 19839-19851. https://doi.org/10.1039/D2TA02111K.

[179] Yang Jiarui, Zhu Chenxi, Li Wen-Hao, Zheng Xusheng, Wang Dingsheng. Organocatalyst supported by a single-atom support accelerates both electrodes used in the chlor-alkali industry via modification of non-covalent interactions, Angewandte Chemie International Edition 2024, 63, e202314382. https://doi.org/10.1002/anie.202314382.

[180] Liu Kaiyuan, Chen Pengwan, Sun Zhiyi, Chen Wenxing, Zhou Qiang, Gao Xin. The atomic interface effect of single atom catalysts for electrochemical hydrogen peroxide production, Nano Research 2023, 16, 10724-10741. https://doi.org/10.1007/s12274-023-5823-7.

[181] Israr Muhammad, Humayun Muhammad, Zhang Jiaqi, Shah Khadim, Tan Xin, Chen Chen, Li Yadong. Ir single atoms on NiFeZn-LDH matrix for exceptional oxygen evolution reaction, Nano Research 2024, 17, 7039-7044. https://doi.org/10.1007/s12274-024-6749-4.

[182] Li Mingyao, Hu Weilin, Wang Boyu, Li Yusen, Jian Wenyuan, Hao Jie, Chen Long, Jia Chuancheng, Guo Xuefeng. Mechanism of hydrogen generation catalyzed by a single atom and its spin regulation, Journal of the American Chemical Society 2025, 147, 6193-6202. https://doi.org/10.1021/jacs.4c17722.

[183] Liu Hao, Chen Lin, Zhu Hao, Sun Qing-Qing, Ding Shi-Jin, Zhou Peng, Wei Zhang David. Atomic layer deposited 2D MoS₂ atomic crystals: from material to circuit, Nano Research 2020, 13, 1644-1650. https://doi.org/10.1007/s12274-020-2787-8.

[184] Qiu Weibin, Qin Shimei, Li Yibao, Cao Ning, Cui Weirong, Zhang Zedong, Zhuang Zechao, Wang Dingsheng, Zhang Yong. Overcoming electrostatic interaction via pulsed electroreduction for boosting the electrocatalytic urea synthesis, Angewandte Chemie International Edition 2024, 63, e202402684. https://doi.org/10.1002/anie.202402684.

[185] Deng Fengxia, Jiang Jizhou, Sirés Ignasi. State-of-the-art review and bibliometric analysis on electro-fenton process, Carbon Letters 2023, 33, 17-34. https://doi.org/10.1007/s42823-022-00420-z.

[186] Xu Nuo, Zhou Haoran, Zhang Mingqiang, Ye Yuchuan, Wang Kaiwen, Zhou Yingtang, Zhu Yunfeng, Zhang Yao. Synergistic effect of Pd single atoms and clusters on the de/re-hydrogenation performance of MgH₂, Journal of Materials Science and Technology 2024, 191, 49-62. https://doi.org/10.1016/j.jmst.2024.01.009.

[187] Lu Tiantian, Wang Huan. Graphdiyne-supported metal electrocatalysts: from nanoparticles and cluster to single atoms, Nano Research 2022, 15, 9764-9778. https://doi.org/10.1007/s12274-022-4157-1.

[188] Zhang Feixiang, Wang Panshuo, Zhu Yandi, Shi Jinlei, Pang Rui, Ren Xiaoyan, Li Shunfang. Highly enhanced room-temperature single-atom catalysis of two-dimensional organic-inorganic multiferroics Cr(half-fluoropyrazine)2 for CO oxidation, Nature Communications 2025, 16, 1580. https://doi.org/10.1038/s41467-025-56863-1.

[189] Pei Shangkun, Wang Sheng, Lu Yuxin, Li Xiang, Wang Bo. Application of metal-based catalysts for fenton reaction: from homogeneous to heterogeneous, from nanocrystals to single atom, Nano Research 2024, 17, 9446-9471. https://doi.org/10.1007/s12274-024-6973-y.

[190] Zou Ren. Joshua Adedeji Bolarin, Gangtie Lei, Wenbo Gao, Zhi Li, Hujun Cao, Ping Chen. Microwave-assisted reduction of Ti species in MgH₂-TiO₂ composite and its effect on hydrogen storage, Chemical Engineering Journal 2022, 450, 138072. https://doi.org/10.1016/j.cej.2022.138072.

[191] Iliescu I., Skryabina N., Fruchart D., Bes A., Lacoste A.. Morphology and microstructure of Mg-Ti-H films deposited by microwave plasma-assisted co-sputtering, Journal of Alloys and Compounds 2017, 708, 489-499. https://doi.org/10.1016/j.jallcom.2017.03.044.

[192] Ren Li, Zhu Wen, Zhang Qiuyu, Lu Chong, Sun Fengzhan, Lin Xi, Zou Jianxin. MgH₂ confinement in MOF-derived N-doped porous carbon nanofibers for enhanced hydrogen storage, Chemical Engineering Journal 2022, 434, 134701. https://doi.org/10.1016/j.cej.2022.134701.

[193] Calizzi M., Venturi F., Ponthieu M., Cuevas F., Morandi V., Perkisas T., Bals S., Pasquini L.. Gas-phase synthesis of Mg-Ti nanoparticles for solid-state hydrogen storage, Physical Chemistry Chemical Physics 2015, 18, 141-148.

[194] Zhang X.L., Liu Y.F., Zhang X., Hu J.J., Gao M.X., Pan H.G.. Empowering hydrogen storage performance of MgH₂ by nanoengineering and nanocatalysis, Materials Today Nano 2020, 9, 100064. https://doi.org/10.1016/j.mtnano.2019.100064.

[195] Hou Quanhui, Yang Xinglin, Zhang Jiaqi. Review on hydrogen storage performance of MgH₂: development and trends, Chemistryselect 2021, 6, 1589-1606. https://doi.org/10.1002/slct.202004476.

[196] Xing Xiaofei, Liu Yijin, Zhang Zhao, Liu Tong. Hierarchical structure carbon-coated CoNi nanocatalysts derived from flower-like bimetal MOFs: enhancing the hydrogen storage performance of MgH₂ under mild conditions, ACS Sustainable Chemistry & Engineering 2023, 11, 4825-4837. https://doi.org/10.1021/acssuschemeng.2c07740.

[197] Sun Yahui, Zhang Xiaoyue, Chen Wei, Ye Jikai, Ju Shunlong, Aguey-Zinsou Kondo-Francois, Xia Guanglin, Sun Dalin, Yu Xuebin. Light-driven reversible hydrogen storage in light-weight metal hydrides enabled by photothermal effect, Small 2022, 18, 2202978. https://doi.org/10.1002/smll.202202978.

[198] Li Zeng-Yi, Sun Li-Xian, Xu Fen, Luo Yu-Mei, Xia Yong-Peng, Wei Sheng, Zhang Chen-Chen, Cheng Ri-Guang, Ye Chao-Feng, Liu Meng-Yuan, Zeng Ju-Lan, Cao Zhong, Pan Hong-Ge. Modulated noble metal/2D MOF heterostructures for improved hydrogen storage of MgH₂, Rare Metals 2024, 43, 1672-1685. https://doi.org/10.1007/s12598-023-02496-6.

[199] Xie Jiaxing, Yao Zhendong, Qi Jiacheng, Gao Ge, Lv Chunju, Li Chao, Fan Meiqiang, Xiao Xuezhang, Chen Lixin. H^-/e^- cooperative transport mechanism for carbon supported nano hydrogen pump in MgH₂, Renewable Energy 2026, 256, 124713. https://doi.org/10.1016/j.renene.2025.124713.

[200] Zhang Haihua, Cao Zhijie, Zhang Meng, Ma Ling, Wang Xiaomeng. Critical role of TiB₂@C on facilitating the dehydrogenation of alanates, Applied Surface Science 2025, 711, 164022. https://doi.org/10.1016/j.apsusc.2025.164022.

[201] Ismail M., Yahya M.S., Sazelee N.A., Ali N.A., Yap F.A. Halim, Mustafa N.S.. The effect of K₂SiF₆ on the MgH₂ hydrogen storage properties, Journal of Magnesium and Alloys 2020, 8, 832-840. https://doi.org/10.1016/j.jma.2020.04.002.

[202] Cai Jianghao, Wang Haobo, Tang Xiaotian, Miao Ziwei, Yao Tongao, Liu Yuxuan, Wang Hongtao, Gao Zhengyang, Yang Weijie. Data-driven evidence for the burst effect in MgH₂ dehydrogenation via analysis of experimental kinetic curves, Journal of Energy Storage 2025, 136, 118450. https://doi.org/10.1016/j.est.2025.118450.

[203] Wang Li, Wu Fuying, Chen Daifen, Bian Ting, Senin Petr, Zhang Liuting. Amorphous scaly high-entropy borides with electron traps for efficient catalysis in solid-state hydrogen storage, International Journal of Minerals, Metallurgy, and Materials 2025, 32, 2713-2722. https://doi.org/10.1007/s12613-024-3033-2.

[204] Fu Yaokun, Zhang Lu, Li Yuan, Guo Sanyang, Yu Han, Wang Wenfeng, Ren Kailiang, Zhang Wei, Han Shumin. Effect of ternary transition metal sulfide FeNi₂S₄ on hydrogen storage performance of MgH₂, Journal of Magnesium and Alloys 2023, 11, 2927-2938. https://doi.org/10.1016/j.jma.2021.11.033.

[205] Qin Yang, Hu Jia, Yang Zimeng, Han Chao, Long Shiteng, Zhang Dingfei, Chen Yu’an, Pan Fusheng. Constructing VO/V₂O₃ interface to enhance hydrogen storage performance of MgH₂, Journal of Magnesium and Alloys 2024, 12, 4877-4886. https://doi.org/10.1016/j.jma.2024.02.012.

[206] Zhu Xueqin, Yang Minjian, Yue Ruiting, Zhang Dasheng, Li Faguo, Wang Danna, Ma Liqiang. Effect of co-doping graphene and anthracite on hydrogen storage of Mg/MgH₂, Solid State Sciences 2024, 147, 107385. https://doi.org/10.1016/j.solidstatesciences.2023.107385.

[207] Yang Zhicheng, Sun Weiqi, Bu Yiting, Zhang Ruoyang, Yang Zexuan, Li Bin, Sun Lixian, Xu Fen, Yu Ting, Guo Wenwei, Liu Yi, Liang Zhengyi. MOF-derived TiO₂ nanosheets loaded with Nb₂O₅ for enhanced catalytic hydrogenation of MgH₂, Chemical Engineering Journal 2025, 522, 167955. https://doi.org/10.1016/j.cej.2025.167955.

[208] Shi Weitao, Hong Feifan, Li Renhuan, Zhao Ruolin, Ding Sizhi, Liu Ziqi, Qing Peilin, Fan Yi, Liu Haizhen, Guo Jin, Lan Zhiqiang. Improved hydrogen storage properties of MgH₂ by mxene (Ti₃C₂) supported MnO₂, Journal of Energy Storage 2023, 72, 108738. https://doi.org/10.1016/j.est.2023.108738.

[209] Wan Haiyi, Yang Xiu, Zhou Shiming, Ran Lei, Lu Yangfan, Chen Yu’an, Wang Jingfeng, Pan Fusheng. Enhancing hydrogen storage properties of MgH₂ using FeCoNiCrMn high entropy alloy catalysts, Journal of Materials Science and Technology 2023, 149, 88-98. https://doi.org/10.1016/j.jmst.2022.11.033.

[210] Jiang Yi, Si Nan, Jiang Wei, Wang Zan, Zhang Hui. FeNiCu-based composite catalyst for hydrogen storage in MgH₂, Chemical Engineering Journal 2024, 499, 156449. https://doi.org/10.1016/j.cej.2024.156449.

[211] Liu Chenxu, Yuan Zeming, Li Xiaoming, Sun Yize, Zhai Tingting, Han Zhonggang, Zhang Liwen, Li Tao. Review on improved hydrogen storage properties of MgH₂ by adding new catalyst, Journal of Energy Storage 2024, 97, 112786. https://doi.org/10.1016/j.est.2024.112786.

[212] Bu Fanqi, Wang Zhenyu, Wajid Ali, Zhai Rui, Liu Ting, Li Yaohua, Ji Xin, Liu Xin, Ding Shujiang, Cheng Yonghong, Zhang Jinying. Solid-state hydrogen storage materials with excellent selective hydrogen adsorption in the presence of alkanes, oxygen, and carbon dioxide by atomic layer amorphous Al₂O₃ encapsulation, Nano-Micro Letters 2025, 18, 78.. https://doi.org/10.1007/s40820-025-01934-7.

[213] Wu Ping, Xiao Lirong, Jiang Manfu, Liu Li, Ni Cui, Hou Chuanxin, Liu Hu, Du Wei, Xie Xiubo. Facile fabrication of hollow cubic NiCo₂O₄ loaded NiS towards hydrogen storage performances improvement of MgH₂, Applied Surface Science 2025, 714, 164496. https://doi.org/10.1016/j.apsusc.2025.164496.

[214] Jangir Mukesh P. Jain Indra. Daniele Mirabile Gattia. Effect of Ti-based additives on the hydrogen storage properties of MgH₂: a review, Hydrogen 2023, 4, 523-541. https://doi.org/10.3390/hydrogen4030034.

[215] Yao Pengyang, Jiang Ying, Liu Yang, Wu Chengzhang, Chou Kuo-Chih, Lyu Tao, Li Qian. Catalytic effect of Ni@rGO on the hydrogen storage properties of MgH₂, Journal of Magnesium and Alloys 2020, 8, 461-471. https://doi.org/10.1016/j.jma.2019.06.006.

[216] Xue Xuebing, Sheng Peng, Feng Dianchen, Sun Wei, Li Jun, Cao Zheng, Zhang Yanghuan. Thermodynamic and kinetic assessment of Ni-substituted Mg-based alloys for hydrogen storage, Energy Technology 2025, e202501076. https://doi.org/10.1002/ente.202501076.

[217] Qi Yichen, Zhang Zeyang, Tang Qinke, Liu Jiangchuan, Shi Rui, Zhang Jiguang, Liu Yana, Wang Jun, Zhang Jiankun, Chen Shihao, Zhu Yunfeng. Synergistic effect of the hydrogen pump and heterostructure enables superior hydrogen storage performance of MgH₂, Chemistry of Materials 2024, 36, 6288-6298. https://doi.org/10.1021/acs.chemmater.4c01234.

[218] Long Shiteng, Qin Yang, Fu Huafeng, Hu Jia, Xue Hansong, Chen Yu’an, Pan Fusheng. Hydrogen storage properties of MgH₂ modified by efficient Co₃V₂O₈ catalyst, Separation and Purification Technology 2024, 341, 126901. https://doi.org/10.1016/j.seppur.2024.126901.

[219] Dan Liang, Wang Hui, Yang Xiaobao, Liu Jiangwen, Ouyang Liuzhang, Zhu Min. Low-temperature solid-state hydrogen storage via efficiently catalyzed MgH₂, Renewable Energy 2024, 231, 121009. https://doi.org/10.1016/j.renene.2024.121009.

[220] Rahwanto A., Ismail I., Nurmalita N., Mustanir, Jalil Z.. Nanoscale Ni as a catalyst in MgH₂ for hydrogen storage material, Journal of Physics: Conference Series 2021, 1882, 12010. https://doi.org/10.1088/1742-6596/1882/1/012010.

[221] Zhang Tianyu, Wang Dingsheng, Liu Junfeng. Periodic single-metal site catalysts: creating homogeneous and ordered atomic-precision structures, Advanced Materials 2024, 36, 2408259. https://doi.org/10.1002/adma.202408259.

[222] Yang Hongchen, Duan Pengfei, Zhuang Zechao, Luo Yaowu, Shen Ji, Xiong Yuli, Liu Xiangwen, Wang Dingsheng. Understanding the dynamic evolution of active sites among single atoms, clusters, and nanoparticles, Advanced Materials 2025, 37, 2415265. https://doi.org/10.1002/adma.202415265.

[223] Zhao Jian, Zhang Yuxiao, Zhuang Zechao, Deng Yating, Gao Ge, Li Jiayi, Meng Alan, Li Guicun, Wang Lei, Li Zhenjiang, Wang Dingsheng. Tailoring d-p orbital hybridization to decipher the essential effects of heteroatom substitution on redox kinetics, Angewandte Chemie International Edition 2024, 63, e202404968. https://doi.org/10.1002/anie.202404968.

[224] Li Qian, Lu Yangfan, Luo Qun, Yang Xiaohua, Yang Yan, Tan Jun, Dong Zhihua, Dang Jie, Li Jianbo, Chen Yuan, Jiang Bin, Sun Shuhui, Pan Fusheng. Thermodynamics and kinetics of hydriding and dehydriding reactions in Mg-based hydrogen storage materials, Journal of Magnesium and Alloys 2021, 9, 1922-1941. https://doi.org/10.1016/j.jma.2021.10.002.

[225] Liu Haizhen, Lu Chenglin, Wang Xinchun, Xu Li, Huang Xiantun, Wang Xinhua, Ning Hua, Lan Zhiqiang, Guo Jin. Combinations of V₂C and Ti₃C₂ MXenes for boosting the hydrogen storage performances of MgH₂, ACS Applied Materials & Interfaces 2021, 13, 13235-13247. https://doi.org/10.1021/acsami.0c23150.

[226] Chi Dinh Linh, Dinh Doan Phuong, Lai Duy Van, Van Nguyen Toan, Thi Pham Trang. Van Thi Hong Phung, Matteo Tonezzer, Duong Duc La, Tung Thanh Nguyen, Trung Bao Tran. Efficient hydrogen storage with nanocrystalline Mg-Ni alloy: enhanced absorption and kinetics via mechanochemical synthesis, Journal of Materials Science 2025, 60, 21457-21472. https://doi.org/10.1007/s10853-025-11628-5.

[227] Yang Xinglin, Li Wenxuan, Zhang Jiaqi, Hou Quanhui. Hydrogen storage performance of Mg/MgH₂ and its improvement measures: research progress and trends, Materials 2023, 16, 1587. https://doi.org/10.3390/ma16041587.

[228] Thongtan Puttimate, Thiangviriya Sophida, Utke Oliver, Utke Rapee. MgH₂-based hydrogen storage tank: kinetics, reversibility, and MWCNTs content, Journal of Physics and Chemistry of Solids 2022, 163, 110578. https://doi.org/10.1016/j.jpcs.2022.110578.

[229] Zhou Chengshang, Li Ke, Huang Tongwen, Sun Pei, Wang Li, Lu Yanshan, Zak Fang Zhigang. in situ formation of nanocrystalline MgH₂ through room temperature hydrogenation, Materials & Design 2022, 218, 110729. https://doi.org/10.1016/j.matdes.2022.110729.

[230] Han Jin, Xu Maowen, Niu Yubin, Li Guan-Nan, Wang Minqiang, Zhang Yan, Jia Min, Li Chang ming. Exploration of K₂Ti₈O₁₇ as an anode material for potassium-ion batteries, Chemical Communications 2016, 52, 11274-11276. https://doi.org/10.1039/C6CC05102B.

[231] Liu Ziqi, Zhao Ruolin, Hong Feifan, Ding Sizhi, Yang Jiakun, Li Renhuan, Fan Yi, Liu Haizhen, Guo Jin, Lan Zhiqiang. Carbon-supported TiN composites serve as catalysts to enhance the (de)hydrogenation kinetics of MgH₂, Journal of Energy Storage 2024, 83, 110760. https://doi.org/10.1016/j.est.2024.110760.

[232] Liu Fang, Wang Jiali, Chen Wei, Zhang Xiaoying, Li Shengting, Li Jinping, Song Yu-Fei, Chu Jinfeng, Liu Guang. In-situ formed Ti/TiH₂ from exfoliated few-layered Ti₃C₂T_x as hydrogen pump enhances the hydrogen storage properties of MgH₂, Journal of Colloid and Interface Science 2025, 700, 138335. https://doi.org/10.1016/j.jcis.2025.138335.

[233] Wan Haiyi, Zhou Shiming, Wei Dan, Qiu Junqi, Ding Zhao, Chen Yu’an, Wang Jingfeng, Pan Fusheng. Enhancing hydrogen storage properties of MgH₂ via reaction-induced construction of Ti/Co/Mn-based multiphase catalytic system, Separation and Purification Technology 2025, 355, 129776. https://doi.org/10.1016/j.seppur.2024.129776.

[234] Dong Chenjie, Li Guansheng, Zhu Jiajing, Cui Jie, Huang Liangjun, Wang Hui. Achieving superior hydrogen sorption kinetics of MgH₂ by addition of Ni-doped TiO₂ catalysts, Journal of Alloys and Compounds 2025, 1010, 177104. https://doi.org/10.1016/j.jallcom.2024.177104.

[235] Shi Qingyun, Gao Yuxing, Zhao Shaolei, Zhang Chunmin, Liu Cong, Wang Chunli, Wang Shaohua, Li Yongzhi, Yin Dongming, Wang Limin, Cheng Yong. Interfacial engineering of fluorinated TiO₂ nanosheets with abundant oxygen vacancies for boosting the hydrogen storage performance of MgH₂, Small 2024, 20, 2307965. https://doi.org/10.1002/smll.202307965.

[236] Sun Wei, Zhang Xin, Li Jun, Cao Zheng, Feng Dianchen, Peng Jun, Qi Yan, Zhao Dongliang, Zhang Yanghuan. Catalytic effect of TiF₃ on hydrogenation and dehydrogenation of Mg-based hydrogen storage alloy prepared by milling, Journal of Physics and Chemistry of Solids 2025, 201, 112626. https://doi.org/10.1016/j.jpcs.2025.112626.

[237] Yong Hui, Chen Yiwan, Ji Yanquan, Wang Shuai, Ma Jiangwei, Liu Baosheng, Hu Jifan, Zhang Yanghuan. In-situ influence of TiF₃ catalyst on the hydrogen storage behavior of Mg-Ni-Y based alloy, Journal of Energy Storage 2024, 77, 110022. https://doi.org/10.1016/j.est.2023.110022.

[238] Lu Heng, Li Jianbo, Xie Tianyu, Zhou Xiang, Ding Zhao, Lu Yangfan, Chen Yu’an, Liu Zhongqing, Li Qian, Pan Fusheng. Synergistic catalytic effects of AlH₃-TiF₃ composites on the hydrogen storage performance of MgH₂, Journal of Physical Chemistry C 2023, 127, 92-98. https://doi.org/10.1021/acs.jpcc.2c07370.

[239] Chen Yongpeng, Zhou Panpan, Bi Jiapeng, Zhu Liuhui, Zhang Lingchao, Yan Chengguo, Jia Yuxiao, Xiao Xuezhang, Wang Xinhua, Chen Lixin. Different poisoning behaviors of impurity gases on AB2-type Ti-based hydrogen storage alloys and their mechanisms, Journal of Energy Chemistry 2026, 114, 350-361. https://doi.org/10.1016/j.jechem.2025.10.033.

[240] Ping Jiehong, Wang Shuai, Shen Xinlong, Yang Guo, Zhang Caiyi, Li Yejun, Leng Haiyan, Han Xingbo. Effect of La doping on tritium storage properties of Ti-based alloys, Progress in Natural Science: Materials International 2025, 35, 934-943. https://doi.org/10.1016/j.pnsc.2025.07.005.

[241] Shen Shaoyang, Li Yongan, Ouyang Liuzhang, Zhang Lan, Zhu Min, Liu Zongwen. V-Ti-based solid solution alloys for solid-state hydrogen storage, Nano-Micro Letters 2025, 17, 175. https://doi.org/10.1007/s40820-025-01672-w.

[242] Youp Song Myoung, Choi Eunho. Effects of milling in hydrogen on magnesium hydride with a hydride-forming titanium additive, Materials Science 2021, 27, 184-191. https://doi.org/10.5755/j02.ms.25056.

[243] Choi Eunho, Youp Song Myoung. Hydriding and dehydriding features of a titanium-added magnesium hydride composite, Materials Science 2020, 26, 6. https://doi.org/10.5755/j01.ms.26.2.22299.

[244] Patelli Nicola, Migliori Andrea, Pasquini Luca. Reversible metal-hydride transformation in Mg-Ti-H nanoparticles at remarkably low temperatures, ChemPhysChem 2019, 20, 1325-1333. https://doi.org/10.1002/cphc.201801186.

[245] Yu Fang, Xu Fen, Sun Li Xian, Fei Zhang Xiang, Wang Lin, Fan Ming Hui. The effect of AlCl₃ and Ti on hydrogen storage performance of 4MgH₂-Li₃AlH₆ system, Materials Science Forum 2016, 852, 876-882. https://doi.org/10.4028/www.scientific.net/MSF.852.876.

[246] Asano Kohta, J Ruud, Westerwaal, Anastasopol Anca, P.A. Lennard, Mooij, Boelsma Christiaan, Ngene Peter, Schreuders Herman, W.H. Eijt Stephan, Dam Bernard. Destabilization of Mg hydride by self-organized nanoclusters in the immiscible Mg-Ti system, The Journal of Physical Chemistry C 2015, 119, 12157-12164. https://doi.org/10.1021/acs.jpcc.5b02275.

[247] Khodaparast V., Rajabi M.. Hydrogen desorption properties of MgH₂-5 Wt% Ti-Mn-Cr composite via combined melt spinning and mechanical alloying, Procedia Materials Science 2015, 11, 611-615. https://doi.org/10.1016/j.mspro.2015.11.092.

[248] Kitabayashi Kouki, Edalati Kaveh, Li Hai‐Wen, Akiba Etsuo, Horita Zenji. Phase transformations in MgH₂-TiH₂ hydrogen storage system by high‐pressure torsion process, Advanced Engineering Materials 2020, 22, 1900027. https://doi.org/10.1002/adem.201900027.

[249] Patelli Nicola, Migliori Andrea, Morandi Vittorio, Pasquini Luca. Interfaces within biphasic nanoparticles give a boost to magnesium-based hydrogen storage, Nano Energy 2020, 72, 104654. https://doi.org/10.1016/j.nanoen.2020.104654.

[250] Pukazhselvan D.. Karakkadparambil Sankaran Sandhya, Devaraj Ramasamy, Aliaksandr Shaula, Duncan Paul Fagg. Transformation of metallic Ti to TiH₂ phase in the Ti/MgH₂ composite and its influence on the hydrogen storage behavior of MgH₂, ChemPhysChem 2020, 21, 1195-1201. https://doi.org/10.1002/cphc.202000031.

[251] Rizo-Acosta Pavel, Cuevas Fermin, Latroche Michel. Hydrides of early transition metals as catalysts and grain growth inhibitors for enhanced reversible hydrogen storage in nanostructured magnesium, Journal of Materials Chemistry A 2019, 7, 23064-23075. https://doi.org/10.1039/c9ta05440e.

[252] Patelli Nicola, Calizzi Marco, Migliori Andrea, Morandi Vittorio, Pasquini Luca. Hydrogen desorption below 150 °C in MgH₂-TiH₂ composite nanoparticles: equilibrium and kinetic properties, The Journal of Physical Chemistry C 2017, 121, 11166-11177. https://doi.org/10.1021/acs.jpcc.7b03169.

[253] Hu Xuechun, Chen Xiaowei, Zhang Xiaoyue, Meng Yang, Xia Guanglin, Yu Xuebin, Sun Dalin, Fang Fang. in situ construction of interface with photothermal and mutual catalytic effect for efficient solar-driven reversible hydrogen storage of MgH₂, Advanced Science 2024, 11, 2400274. https://doi.org/10.1002/advs.202400274.

[254] Jangir Mukesh, Jain Ankur, Agarwal Shivani, Zhang Tengfei, Kumar Sanjay, Selvaraj Suganthamalar. Takayuki Ichikawa, I. P. Jain. The enhanced de/re-hydrogenation performance of MgH₂ with TiH₂ additive, International Journal of Energy Research 2018, 42, 1139-1147. https://doi.org/10.1002/er.3911.

[255] Sun Wenpei. The hydrogen storage performance of a 4MgH₂LiAlH₄TiH₂ composite system, Journal of Alloys and Compounds 2016, 676, 557-564. https://doi.org/10.1016/j.jallcom.2016.03.194.

[256] Lotoskyy Mykhaylo, Denys Roman, A Volodymyr, Yartys, Eriksen Jon, Goh Jonathan. Serge Nyallang Nyamsi, Cordellia Sita, Franscious Cummings. An outstanding effect of graphite in nano-MgH₂-TiH₂ on hydrogen storage performance, Journal of Materials Chemistry A 2018, 6, 10740-10754. https://doi.org/10.1039/C8TA02969E.

[257] Zhou Chengshang, Zak Fang Zhigang, C Robert, Bowman. Stability of catalyzed magnesium hydride nanocrystalline during hydrogen cycling. part I: kinetic analysis, The Journal of Physical Chemistry C 2015, 119, 22261-22271. https://doi.org/10.1021/acs.jpcc.5b06190.

[258] Zhang Liuting, Lu Xiong, Ji Liang, Yan Nianhua, Sun Ze, Zhu Xinqiao. Catalytic effect of facile synthesized TiH_{1. 971} nanoparticles on the hydrogen storage properties of MgH₂, Nanomaterials 2019, 9, 1370. https://doi.org/10.3390/nano9101370.

[259] Pan Yong. Theoretical discovery of high capacity hydrogen storage metal tetrahydrides, International Journal of Hydrogen Energy 2019, 44, 18153-18158. https://doi.org/10.1016/j.ijhydene.2019.05.145.

[260] Zhang Yao, Zhuang Xiangyang, Zhu Yunfeng, Wan Neng, Li Liquan, Dong Jun. Synergistic effects of TiH₂ and Pd on hydrogen desorption performances of MgH₂, International Journal of Hydrogen Energy 2015, 40, 16338-16346. https://doi.org/10.1016/j.ijhydene.2015.09.029.

[261] Zhang Liuting. Excellent catalysis of Mn₃O₄ nanoparticles on the hydrogen storage properties of MgH₂: an experimental and theoretical study, Nanoscale Advances 2020, 2, 1666-1675. https://doi.org/10.1039/D0NA00137F.

[262] Liu Meichen, Lei Zhiping, Ke Qingping, Cui Peixin, Wang Jiancheng, Yan Jingchong, Li Zhanku, Shui Hengfu, Ren Shibiao, Wang Zhicai, Kong Ying, Kang Shigang. Regulation of hydrogen evolution performance of titanium oxide-carbon composites at high current density with a Ti-O hybrid orbital, Carbon Energy 2022, 4, 480-490. https://doi.org/10.1002/cey2.162.

[263] Chen Man, Xiao Xuezhang, Zhang Meng, Mao Jianfeng, Zheng Jiaguang, Liu Meijia, Wang Xuancheng, Chen Lixin. Insights into 2D graphene-like TiO₂ (B) nanosheets as highly efficient catalyst for improved low-temperature hydrogen storage properties of MgH₂, Materials Today Energy 2020, 16, 100411. https://doi.org/10.1016/j.mtener.2020.100411.

[264] Jardim P.M., Conceição M.O.T. da, Brum M.C., Santos D.S. dos. Hydrogen sorption kinetics of ball-milled MgH₂-TiO₂ based 1D nanomaterials with different morphologies, International Journal of Hydrogen Energy 2015, 40, 17110-17117. https://doi.org/10.1016/j.ijhydene.2015.06.172.

[265] Shao Yuting, Gao Haiguang, Tang Qinke, Liu Yana, Liu Jiangchuan, Zhu Yunfeng, Zhang Jiguang, Li Liquan, Hu Xiaohui, Ba Zhixin. Ultra-fine TiO₂ nanoparticles supported on three-dimensionally ordered macroporous structure for improving the hydrogen storage performance of MgH₂, Applied Surface Science 2022, 585, 152561. https://doi.org/10.1016/j.apsusc.2022.152561.

[266] Pukazhselvan D.. Narendar Nasani, Pedro Correia, Enrique Carbó-Argibay, Gonzalo Otero-Irurueta, Daniel G. Stroppa, Duncan Paul Fagg. Evolution of reduced Ti containing phase(s) in MgH₂/TiO₂ system and its effect on the hydrogen storage behavior of MgH₂, Journal of Power Sources 2017, 362, 174-183. https://doi.org/10.1016/j.jpowsour.2017.07.032.

[267] Pukazhselvan D.. Role of chemical interaction between MgH₂ and TiO₂ additive on the hydrogen storage behavior of MgH₂, Applied Surface Science 2017, 420, 6. https://doi.org/10.1016/j.apsusc.2017.05.182.

[268] Dai Min. Joshua Adedeji Bolarin, Gangtie Lei, Zhi Li, Teng He, Hujun Cao, Ping Chen. Potassium hydride reduced black TiO_2-x for boosting the hydrogenation of magnesium at room temperature, Journal of Alloys and Compounds 2022, 897, 162750. https://doi.org/10.1016/j.jallcom.2021.162750.

[269] Vujasin Radojka, Mraković Ana, Kurko Sandra, Novaković Nikola, Matović Ljiljana. Jasmina Grbović Novaković Sanja Milošević. Catalytic activity of titania polymorphs towards desorption reaction of MgH₂, International Journal of Hydrogen Energy 2016, 41, 4703-4711. https://doi.org/10.1016/j.ijhydene.2016.01.095.

[270] Kumar Sanjay. Tailoring the hydrogen absorption desorption’s dynamics of Mg-MgH₂ system by titanium suboxide doping, International Journal of Hydrogen Energy 2017, 42, 8. https://doi.org/10.1016/j.ijhydene.2017.07.128.

[271] Sun Ze, Lu Xiong. Farai Michael Nyahuma, Nianhua Yan, Jiankun Xiao, Shichuan Su, Liuting Zhang. Enhancing hydrogen storage properties of MgH₂ by transition metals and carbon materials: a brief review, Frontiers in Chemistry 2020, 8, 552. https://doi.org/10.3389/fchem.2020.00552.

[272] Xing Xiaofei, Wei Mingxing, Cao Boyuan, Zhang Zhao, Liu Tong. Simultaneously nanoconfining Mg and loading multiple metal single atoms catalysts with N-doped carbon to achieve room-temperature dehydrogenation, Small 2025, 21 (47), e08519. https://doi.org/10.1002/smll.202508519.

[273] Lu Xiaohui, Yang Xinglin, Liang Xiaoxu, Hou Quanhui, Kong Jie, Su Jianye. TiO₂_ZnTiO₃ with carbon nanotubes catalytically improve the hydrogen storage characteristics of MgH₂, Journal of Power Sources 2024, 623, 235455. https://doi.org/10.1016/j.jpowsour.2024.235455.

[274] Zhang Xin, Leng Zihan, Gao Mingxia, Hu Jianjiang, Du Fang, Yao Jianhua, Pan Hongge, Liu Yongfeng. Enhanced hydrogen storage properties of MgH₂ catalyzed with carbon-supported nanocrystalline TiO₂, Journal of Power Sources 2018, 398, 183-192. https://doi.org/10.1016/j.jpowsour.2018.07.072.

[275] Zhang Meng. Synergistic catalysis in monodispersed transition metal oxide nanoparticles anchored on amorphous carbon for excellent low-temperature dehydrogenation of magnesium hydride, Materials Today Energy 2019, 12, 146-154. https://doi.org/10.1016/j.mtener.2019.01.001.

[276] Plerdsranoy Praphatsorn, Chanthee Songwuit, Utke Rapee. Compaction of LiBH₄-MgH₂ doped with MWCNTs-TiO₂ for reversible hydrogen storage, International Journal of Hydrogen Energy 2017, 42, 978-986. https://doi.org/10.1016/j.ijhydene.2016.11.066.

[277] Puszkiel J.A., Riglos M.V. Castro, Karimi F., Santoru A., Pistidda C., Klassen T., Colbe J.M. Bellosta von, Dornheim M.. Changing the dehydrogenation pathway of LiBH₄-MgH₂ via nanosized lithiated TiO₂, Physical Chemistry Chemical Physics 2017, 19, 7455-7460. https://doi.org/10.1039/C6CP08278E.

[278] Yuan Hongxin, Hua Jianxin, Wei Wei, Zhang Miao, Hao Yue, Chang Jingjing. Progress and prospect of flexible MXene-based energy storage, Carbon Energy 2025, 7, e639. https://doi.org/10.1002/cey2.639.

[279] Fei Ling, Lei Lei, Xu Hui, Guo Xinghua, Chen Bo, Han Xu, Chen Xun, Huang Qing, Wang Degao. Ion transport behaviors in MXenes for electrochemical energy storage and conversion, Carbon Energy 2025, e678. https://doi.org/10.1002/cey2.678.

[280] Deng Yanli, Chen Yaqing, Liu Wei, Wu Lili, Wang Zhou, Xiao Dan, Meng Decheng, Jiang Xingguo, Liu Jiurong, Zeng Zhihui, Wu Na, Energy Carbon. Transparent electromagnetic interference shielding materials using MXene, 2024, 6, e593. https://doi.org/10.1002/cey2.593.

[281] Cai Yanqing, Chen Xinggang, Xu Ying, Zhang Yalin, Liu Huijun, Zhang Hongjuan, Tang Jing. Ti₃C₂T MXene/carbon composites for advanced supercapacitors: Synthesis, progress, and perspectives, Carbon Energy 2024, 6, e501. https://doi.org/10.1002/cey2.501.

[282] Duan Xing-Qing, Li Guang-Xu, Zhang Wen-Hui, Luo Hui, Tang Hai-Mei, Xu Li, Sheng Peng, Wang Xin-Hua, Huang Xian-Tun, Huang Cun-Ke, Lan Zhi-Qiang, Zhou Wen-Zheng, Guo Jin, Bin Ismail Mohammd, Liu Hai-Zhen. Ti₃AlCN MAX for tailoring MgH₂ hydrogen storage material: from performance to mechanism, Rare Metals 2023, 42, 1923-1934. https://doi.org/10.1007/s12598-022-02231-7.

[283] Lakhnik A.M., Kirian I.M., Rud A.D.. The Mg/MAX-phase composite for hydrogen storage, International Journal of Hydrogen Energy 2022, 47, 7274-7280. https://doi.org/10.1016/j.ijhydene.2021.02.081.

[284] Wang Ke, Du Hufei, Wang Zeyi, Gao Mingxia, Pan Hongge, Liu Yongfeng. Novel MAX-phase Ti₃AlC₂ catalyst for improving the reversible hydrogen storage properties of MgH₂, International Journal of Hydrogen Energy 2017, 42, 4244-4251. https://doi.org/10.1016/j.ijhydene.2016.10.073.

[285] Yang Zexuan, Wu Jiaao, Wang Yazhou, Wang Shunxiang, Zou Yongjin, Xiang Cuili, Xu Fen, Sun Lixian, Shen Chua Yong. Improved hydrogen storage performance of magnesium hydride catalyzed by two dimensional Ti₃C₂-coated NbN, Journal of Alloys and Compounds 2025, 1029, 180752. https://doi.org/10.1016/j.jallcom.2025.180752.

[286] Lu Xiaohui, Yang Xinglin, Liang Xiaoxu, Su Jianye, Kong Jie, Pan Yijiang, Hou Quanhui. MXene Ti₃C₂@NiO catalysts for improving the kinetic performance of MgH₂ hydrogen storage, Journal of Alloys and Compounds 2025, 1010, 177963. https://doi.org/10.1016/j.jallcom.2024.177963.

[287] Dai Zi-Yin, Wu Ping, Xiao Li-Rong, Kimura Hideo, Hou Chuan-Xin, Sun Xue-Qin, Guo Si-Jie, Du Wei, Xie Xiu-Bo. Non-stoichiometric Ni₃ZnC_{0. 7} carbide loading on melamine sponge-derived carbon for hydrogen storage performance improvement of MgH₂, Rare Metals 2025, 44, 515-530. https://doi.org/10.1007/s12598-024-02943-y.

[288] Duan Congwen, Su Yaohua, Zhang Ziyan, Cao Yuxuan, Huang Haixiang, Fan Yuchen, Tian Yating, Hu Lianxi, Wang Fei, Li Ming, Wu Ying. A phase-transition catalyst bidirectionally enhances the hydrogen absorption/desorption kinetics of Mg/MgH₂, Energy & Fuels 2025, 39 (23), 11437-11454. https://doi.org/10.1021/acs.energyfuels.5c01654.

[289] Wang Xiaojiao, Yuan Zhenluo, Shi Yang, Li Shangsheng, Mi Guofa, Peng Qiuming, Han Shumin, Fan Yanping, Liu Baozhong.Effective catalytic effects of Mo₂C MXene on the hydrogen storage in magnesium hydride, Journal of Magnesium and Alloys 2025. https://doi.org/10.1016/j.jma.2025.04.029.

[290] Lv Mei-Ling, Zheng Jia-Guang, Xia Ao, Zhang Qing-Bo, Ma Zhen-Xuan, Su Chao, Ge Lei. Bimetallic Ti₂NbC₂ MXene as an efficient catalyst for reversible hydrogen storage in magnesium hydride, Rare Metals 2025, 44, 2489-2501. https://doi.org/10.1007/s12598-024-03140-7.

[291] Jia Yuxiao, Wang Xuancheng, Hu Leijie, Xiao Xuezhang, Zhang Shuoqing, He Jiahuan, Qi Jiacheng, Lv Ling, Xu Fen, Sun Lixian, Chen Lixin. Carbon composite support improving catalytic effect of NbC nanoparticles on the low-temperature hydrogen storage performance of MgH₂, Journal of Materials Science and Technology 2023, 150, 65-74. https://doi.org/10.1016/j.jmst.2022.11.044.

[292] Tian Zhihui, Wang Zexuan, Yao Pufan, Xia Chaoqun, Yang Tai, Li Qiang. Hydrogen storage behaviors of magnesium hydride catalyzed by transition metal carbides, International Journal of Hydrogen Energy 2021, 46 (80), 40203-40216. https://doi.org/10.1016/j.ijhydene.2021.09.212.

[293] Li Jingxiao, Wang Shun, Du Yulei, Liao Wenhe. Catalytic effect of Ti₂C MXene on the dehydrogenation of MgH₂, International Journal of Hydrogen Energy 2019, 44 (13), 6787-6794. https://doi.org/10.1016/j.ijhydene.2019.01.189.

[294] Liu Yongfeng, Du Hufei, Zhang Xin, Yang Yaxiong, Gao Mingxia, Pan Hongge. Superior catalytic activity derived from a two-dimensional Ti₃C₂ precursor towards the hydrogen storage reaction of magnesium hydride, Chemical Communications 2016, 52 (4), 705-708. https://doi.org/10.1039/C5CC08801A.

[295] El-Eskandarany M.S.. Synergistic dosing effect of TiC/FeCr nanocatalysts on the hydrogenation/dehydrogenation kinetics of nanocrystalline MgH₂ powders, Energy 2016, 104, 158-170. https://doi.org/10.1016/j.energy.2016.03.104.

[296] Hu Miaomiao. TiC_X-decorated Mg nanoparticles confined in carbon shell: Preparation and catalytic mechanism for hydrogen storage, Journal of Alloys and Compounds 2020, 817, 152813. https://doi.org/10.1016/j.jallcom.2019.152813.

[297] Zhang Jianfeng, Li Zhinian, Wu Yuanfang, Guo Xiumei, Ye Jianhua, Yuan Baolong, Yuan Huiping, Wang Shumao, Jiang Lijun.Significant thermodynamic destabilization and superior hydrogen storage properties of nanocrystalline Mg-20 wt % Ti-Cr-V_x (x= 0. 4, 0. 6, 0. 8; Ti/Cr = 2: 3) composites synthesized by reactive ball milling, The Journal of Physical Chemistry C 2019, 123, 15963-15976. https://doi.org/10.1021/acs.jpcc.9b03161.

[298] Wang Chenlu, Hou Xiaojiang, Cao Qianhong, Zhao Duode, Li Danting, Xie Xinlei, Zhu Peixuan, Ye Xiaohui, Suo Guoquan, Yang Guang, Xu Guangsheng. Multi-component synergistic catalytic effect to enhance hydrogen storage kinetic of non-activated MgH₂-Ni/Ti₃C₂T_x composites, Journal of Energy Storage 2025, 132, 117811. https://doi.org/10.1016/j.est.2025.117811.

[299] Wang Zeyi, Zhang Xuelian, Ren Zhuanghe, Liu Yong, Hu Jianjiang, Li Haiwen, Gao Mingxia, Pan Hongge, Liu Yongfeng. in situ formed ultrafine NbTi nanocrystals from a NbTiC solid-solution MXene for hydrogen storage in MgH₂, Journal of Materials Chemistry A 2019, 7, 14244-14252. https://doi.org/10.1039/C9TA03665B.

[300] El-Eskandarany M. Sherif. Fahad Al-Ajmi, Mohammad Banyan, Ahmed Al-Duweesh. Synergetic effect of reactive ball milling and cold pressing on enhancing the hydrogen storage behavior of nanocomposite MgH₂/ 10 wt% TiMn₂ binary system, International Journal of Hydrogen Energy 2019, 44, 26428-26443. https://doi.org/10.1016/j.ijhydene.2019.08.093.

[301] Noor Aliah Abdul Majid, Maeda Naoki, Notomi Mitsuo. Improved hydrogen desorption properties of magnesium hydride with TiFe_{0. 8}Mn_{0. 2}, graphite and iron addition, International Journal of Hydrogen Energy 2019, 44, 29189-29195. https://doi.org/10.1016/j.ijhydene.2019.02.190.

[302] Mohamed Sherif El-Eskandarany. Metallic glassy Ti₂Ni grain-growth inhibitor powder for enhancing the hydrogenation/dehydrogenation kinetics of MgH₂, RSC Advances 2019, 9, 1036-1046. https://doi.org/10.1039/C8RA08200F.

[303] Zhou Chengshang, Zak Fang Zhigang, Sun Pei, Xu Lei, Liu Yong. Capturing low-pressure hydrogen using V Ti Cr catalyzed magnesium hydride, Journal of Power Sources 2019, 413, 139-147. https://doi.org/10.1016/j.jpowsour.2018.12.048.

[304] Nachev S.. Mechanical behavior of highly reactive nanostructured MgH₂, Int. J. Hydrogen Energy 2015, 40, 17065-17074. https://doi.org/10.1016/j.ijhydene.2015.05.022.

[305] Kral L., Cermak J.. Improvement of hydrogen storage properties of Mg by catalytic effect of Al-containing phases in Mg-Al-Ti-Zr-C powders, International Journal of Hydrogen Energy 2019, 44, 13561-13568. https://doi.org/10.1016/j.ijhydene.2019.03.188.

[306] Zhang Liuting. Enhanced hydrogen storage properties of MgH₂ by the synergetic catalysis of Zr_0.4Ti_0.6Co nanosheets and carbon nanotubes, Applied Surface Science 2020, 504, 144465. https://doi.org/10.1016/j.apsusc.2019.144465.

[307] Zavalii І.Yu., Berezovets’ V.V., Denys R.V.. Nanocomposites based on magnesium for hydrogen storage: achievements and prospects (a survey), Materials Science 2019, 54, 611-626. https://doi.org/10.1007/s11003-019-00226-x.

[308] Lv Haitao, Wang Liangrui, Ou Xiulong, Li Zhiming. Effect of TiS₂ on hydrogen absorption and desorption performance of mechanically ball-milled Mg₉₅Ce₅ alloy, Symmetry 2025, 17, 71. https://doi.org/10.3390/sym17010071.

[309] Zhang Xin, Zhang Xuelian, Ren Zhuanghe, Hu Jianjiang, Gao Mingxia, Pan Hongge, Liu Yongfeng. Amorphous-carbon-supported ultrasmall TiB₂ nanoparticles with high catalytic activity for reversible hydrogen storage in NaAlH₄, Front. Chem. 2020, 8. https://doi.org/10.3389/fchem.2020.00419.

[310] Dong Chunyang, Li Yinlong, Cheng Danyang, Zhang Mengtao, Liu Jinjia, Wang Yang-Gang, Xiao Dequan, Ma Ding. Supported metal clusters: fabrication and application in heterogeneous catalysis, ACS Catalysis 2020, 10, 11011-11045. https://doi.org/10.1021/acscatal.0c02818.

[311] Zhang Lina, Zhang Ke, Wang Chengming, Liu Yanyan, Wu Xianli, Peng Zhikun, Cao Huaqiang, Li Baojun, Jiang Jianchun. Advances and prospects in metal-organic frameworks as key nexus for chemocatalytic hydrogen production, Small 2021, 17, 2102201. https://doi.org/10.1002/smll.202102201.

[312] Guo Bowen, Wang Zekun, Zheng Lei, Mo Guang, Zhou Hongjun, Luo Dan. Confined cobalt single-atom catalysts with strong electronic metal-support interactions based on a biomimetic self-assembly strategy, Carbon Energy 2024, 6, e554. https://doi.org/10.1002/cey2.554.

[313] Wang Xin, Yang Xiaoli, Pei Guangxian, Yang Jifa, Liu Junzhe, Zhao Fengwang, Jin Fayi, Jiang Wei, Ben Haoxi, Zhang Lixue. Strong metal-support interaction boosts the electrocatalytic hydrogen evolution capability of Ru nanoparticles supported on titanium nitride, Carbon Energy 2024, 6, e391. https://doi.org/10.1002/cey2.391.

[314] Fan Yanping, Yuan Zhenluo, Zou Guodong, Zhang Qingrui, Liu Baozhong, Peng Qiuming. Two-dimensional MXene/A-TiO₂ composite with unprecedented catalytic activation for sodium alanate, Catal. Today 2018, 318, 167-174. https://doi.org/10.1016/j.cattod.2017.11.018.

[315] Zhu Wen, Panda Subrata, Lu Chong, Ma Zhewen, Khan Darvaish, Dong Jinjian, Sun Fengzhan, Xu Hao, Zhang Qiuyu, Zou Jianxin. Using a self-assembled two-dimensional MXene-based catalyst (2D-Ni@Ti₃C₂) to enhance hydrogen storage properties of MgH₂, ACS Applied Materials & Interfaces 2020, 12, 50333-50343. https://doi.org/10.1021/acsami.0c12767.

[316] Gao Haiguang, Shao Yuting, Shi Rui, Liu Yana, Zhu Jinglian, Liu Jiangchuan, Zhu Yunfeng, Zhang Jiguang, Li Liquan, Hu Xiaohui. Effect of few-layer Ti₃C₂T_x supported nano-Ni via self-assembly reduction on hydrogen storage performance of MgH₂, ACS Applied Materials & Interfaces 2020, 12, 47684-47694. https://doi.org/10.1021/acsami.0c15686.

[317] Gao Haiguang, Liu Yana, Zhu Yunfeng, Zhang Jiguang, Li Liquan. Catalytic effect of sandwich-like Ti₃C₂/TiO₂(A)-C on hydrogen storage performance of MgH₂, Nanotechnology 2020, 31, 115404. https://doi.org/10.1088/1361-6528/ab5979.

[318] Song Mengchen, Zhang Liuting, Zheng Jiaguang, Yu Zidong, Wang Shengnan. Constructing graphene nanosheet-supported FeOOH nanodots for hydrogen storage of MgH₂, International Journal of Minerals, Metallurgy and Materials 2022, 29, 1464-1473. https://doi.org/10.1007/s12613-021-2393-0.

[319] Wu Zhaojie, Fang Jianhua, Liu Na, Wu Jiang, Kong Linglan. The improvement in hydrogen storage performance of MgH₂ enabled by multilayer Ti₃C₂, Micromachines 2021, 12, 1190. https://doi.org/10.3390/mi12101190.

[320] Isabel Llamas Jansa. Georgios N. Kalantzopoulos, Kari Nordholm, Bjørn C. Hauback. Destabilization of NaBH₄ by transition metal fluorides, Molecules 2020, 25, 780. https://doi.org/10.3390/molecules25040780.

[321] Pang Yuepeng. in situ formation of Al₃Ti, MgF₂ and Al and their superior synergetic effects on reversible hydrogen storage of MgH₂, Catal. Today 2018, 318, 107-112. https://doi.org/10.1016/j.cattod.2017.10.035.

[322] Christian Bonatto Minella, Garroni Sebastiano, Pistidda Claudio, Dolors Baró Maria, Gutfleisch Oliver, Klassen Thomas, Dornheim Martin. Sorption properties and reversibility of Ti(IV) and Nb(V)-fluoride doped-Ca(BH₄)₂-MgH₂ system, Journal of Alloys and Compounds 2015, 622, 989-994. https://doi.org/10.1016/j.jallcom.2014.11.038.

[323] Zhang Tiebang. Non-isothermal synergetic catalytic effect of TiF₃ and Nb₂O₅ on dehydrogenation high-energy ball milled MgH₂, Materials Chemistry and Physics 2016, 183, 65-75. https://doi.org/10.1016/j.matchemphys.2016.08.002.

[324] Mustafa N.S., Ismail M.. Enhanced hydrogen storage properties of K₂TiF₆ doped Mg-Na-Al composite system, Materials Chemistry and Physics 2018, 217, 350-356. https://doi.org/10.1016/j.matchemphys.2018.06.060.

[325] Nurul Nafiqah Itam Sulaiman. Muhammad Syarifuddin Yahya, Noratiqah Sazelee, Nurul Amirah Ali, Nurul Shafikah Mustafa, Muhammad Firdaus Asyraf Abdul Halim Yap, Mohammad Ismail. An investigation on the addition of SrTiO₃ to the hydrogen storage properties of the 4MgH₂-Li₃AlH₆ composite, International Journal of Energy Research 2022, 46, 8030-8041. https://doi.org/10.1002/er.7704.

[326] Mao Jianfeng, Guo Zaiping, Leng Haiyan, Wu Zhu, Guo Yanhui, Yu Xuebin, Liu Huakun. Reversible hydrogen storage in destabilized LiAlH₄-MgH₂-LiBH₄ ternary-hydride system doped with TiF₃, Journal of Physical Chemistry C 2010, 114, 11643-11649. https://doi.org/10.1021/jp1012208.

[327] Ismail M., Yap F.A. Halim, Sulaiman N.N., Ishak M.H.I.. Hydrogen storage properties of a destabilized MgH₂Sn system with TiF₃ addition, Journal of Alloys and Compounds 2016, 678, 297-303. https://doi.org/10.1016/j.jallcom.2016.03.168.

[328] Yang Lili, Li Shujing, Chen Jiawen, Liu Jiangchuan, Zhu Yunfeng, Liu Yana, Zhang Jiguang, Qiao Yajing, Ba Zhixin, Li Liquan. Significantly improved hydrogen storage properties of Mg₉₀Al₁₀ catalyzed by TiF₃, Journal of Alloys and Compounds 2022, 908, 164581. https://doi.org/10.1016/j.jallcom.2022.164581.

[329] Mazlan N.S.C., Yap F.A. Halim, Yahya M.S., Mohamed S.B., Sazelee N.A., Ali N.A., Jusoh I., Ismail M.. Influence of TiF₃ catalyst on the enhancement of hydrogen storage properties of Mg-Na-Al-Li-B composite system, Journal of Energy Storage 2023, 71, 108097. https://doi.org/10.1016/j.est.2023.108097.

[330] Hou Xiaojiang, Hu Rui, Yang Yanling, Feng Lei. Isothermal activation, thermodynamic and hysteresis of MgH₂ hydrides catalytically modified by high-energy ball milling with MWCNTs and TiF₃, International Journal of Hydrogen Energy 2017, 42, 22953-22964. https://doi.org/10.1016/j.ijhydene.2017.07.099.

[331] Su Wei. Effect of multi-wall carbon nanotubes supported nano-nickel and TiF₃ addition on hydrogen storage properties of magnesium hydride, Journal of Alloys and Compounds 2016, 669, 8-18. https://doi.org/10.1016/j.jallcom.2016.01.253.

[332] Thiangviriya Sophida, Plerdsranoy Praphatsorn, Sitthiwet Chongsutthamani, Dansirima Palmarin, Thongtan Puttimate, Eiamlamai Priew, Utke Oliver, Utke Rapee. MgH₂-TiF₄-MWCNTs based hydrogen storage tank with central tube heat exchanger, International Journal of Hydrogen Energy 2019, 44, 20173-20182. https://doi.org/10.1016/j.ijhydene.2019.06.002.

[333] Kong Qianqian, Zhang Huanhuan, Yuan Zhenluo, Liu Jiameng, Li Lixin, Fan Yanping, Fan Guangxin, Liu Baozhong, Hamamelis-like. K₂Ti₆O₁₃ Synthesized by Alkali Treatment of Ti₃C₂ MXene: Catalysis for Hydrogen Storage in MgH₂, ACS Sustainable Chemistry & Engineering 2020, 8, 4755-4763. https://doi.org/10.1021/acssuschemeng.9b06936.

[334] Zhang Liuting, Xiao Xuezhang, Chen Lixin, Fan Xiulin, Zheng Jiaguang, Huang Xu. Correction: enhanced hydrogen storage properties of MgH₂ with numerous hydrogen diffusion channels provided by Na₂Ti₃O₇ nanotubes, Journal of Materials Chemistry A 2017, 5, 24015-24015. https://doi.org/10.1039/C7TA90253K.

[335] Xian Kaicheng, Wu Meihong, Gao Mingxia, Wang Shun, Li Zhenglong, Gao Panyu, Yao Zhihao, Liu Yongfeng, Sun Wenping, Pan Hongge. A unique nanoflake‐shape bimetallic Ti-Nb oxide of superior catalytic effect for hydrogen storage of MgH₂, Small 2022, 2107013. https://doi.org/10.1002/smll.202107013.

[336] Pukazhselvan D.. Narendar Nasani, Tao Yang, Devaraj Ramasamy, Aliaksandr Shaula, Duncan Paul Fagg. Chemically transformed additive phases in Mg₂TiO₄ and MgTiO₃ loaded hydrogen storage system MgH₂, Applied Surface Science 2019, 472, 99-104. https://doi.org/10.1016/j.apsusc.2018.04.052.

[337] Wang J.S., Zhang W., Han S.M., Qin F..Improvement in hydrogen storage properties of MgH₂ catalyzed with BaTiO₃additive, IOP Conference Series: Materials Science and Engineering 2018, 292, 012053.

[338] Joshua Adedeji Bolarin, Zhang Zhao, Cao Hujun, Li Zhi, He Teng, Chen Ping. Room temperature hydrogen absorption of Mg/MgH₂ catalyzed by BaTiO₃, Journal of Physical Chemistry C 2021, 125, 19631-19641. https://doi.org/10.1021/acs.jpcc.1c05560.

[339] Zhang Tengfei. Enhancement of hydrogen desorption kinetics in magnesium hydride by doping with lithium metatitanate, Journal of Alloys and Compounds 2017, 711, 400-405. https://doi.org/10.1016/j.jallcom.2017.03.361.

[340] Mao Yuchen, Han Mengjiao, Li Ziming, Huang Liangjun, Zhang Wei, Wang Hui, Ouyang Liuzhang, Ma Xiuliang, Zhu Min. Giant tuning on de/hydrogenation thermodynamics by constructing internal strain field in AB2 type hydrogen storage alloys, Acta Materialia 2025, 301, 121551. https://doi.org/10.1016/j.actamat.2025.121551.

[341] Song Wenjie, Ma Wenhao, He Shuai, Chen Wei, Shen Jianghua, Sun Dalin, Wei Qiuming, Yu Xuebin. TiO₂@C catalyzed hydrogen storage performance of Mg-Ni-Y alloy with LPSO and ternary eutectic structure, Journal of Magnesium and Alloys 2024, 12, 767-778. https://doi.org/10.1016/j.jma.2023.04.002.

[342] Zhang Jiyue, Wang Wenda, Chen Xiaowei, Jin Jinlong, Yan Xiaojun, Huang Jianmei. Single-atom Ni supported on TiO₂ for catalyzing hydrogen storage in MgH₂, Journal of the American Chemical Society 2024, 146, 10432-10442. https://doi.org/10.1021/jacs.3c13970.

[343] Jia Bohua, Zhang Jingjing, Chen Xiaowei, Zhang Jiyue, Han Baoxin, Wang Wentao, Yan Xiaojun, Shui Jianglan, Huang Jianmei. Electronic structure modulation of Nb₂O₅ by Ru single atoms enabling efficient hydrogen storage of magnesium hydrides, Angewandte Chemie International Edition 2025, 64, e202511139. https://doi.org/10.1002/anie.202511139.

[344] Li Yinghui, Ren Li, Yao Yingying, Zhao Yingyan, Xu Hao, Li Zhao, Li Zi, Dai Xiaohan, Tian Yuhan, Cao Shusheng, Lin Xi, Ye Chongnan, Züttel Andreas, Zou Jianxin. A single-atom interface engineering strategy to promote hydrogen sorption performances of magnesium hydride, Advanced Functional Materials 2025, 35, 2417915. https://doi.org/10.1002/adfm.202417915.

[345] Liu Yafei, Yue Mengyuan, Guo Yusang, Jiang Yaru, Sun Yu, Feng Lizhuang, Wang Yijing. Catalytic effect of carbon-supported NiCoFeCuMg high-entropy alloy nanocatalysts on hydrogen storage properties of MgH₂, Journal of Magnesium and Alloys 2025, 13, 1232-1242. https://doi.org/10.1016/j.jma.2024.04.031.

[346] Zhong Tao, Zhang Haoyu, Song Mengchen, Jiang Yiqun, Shang Danhong, Wu Fuying, Zhang Liuting. FeCoNiCrMo high entropy alloy nanosheets catalyzed magnesium hydride for solid-state hydrogen storage, International Journal of Minerals, Metallurgy, and Materials 2023, 30, 2270-2279. https://doi.org/10.1007/s12613-023-2669-7.

[347] Jia Manman, Jiang Jietao, Tian Jingyi, Wang Xizhang, Yang Lijun, Wu Qiang, Hu Zheng. Ultrasmall high-entropy alloy nanoparticles on hierarchical N-doped carbon nanocages for tremendous electrocatalytic hydrogen evolution, Nano Research 2024, 17, 9518-9524. https://doi.org/10.1007/s12274-024-6924-7.

[348] Li Yinghui, Zhao Yingyan, Cao Shusheng, Li Zi, Shen Yueqing, Kuddusi Yasemen, Lu Chong, Lin Xi, Züttel Andreas, Ye Chongnan, Zou Jianxin. Study on mechanisms of two-step hydrogen sorption in a MgH₂-TiCrMnFeZr high-entropy alloy composite, Journal of Materials Chemistry A 2025, 13, 23632-23642. https://doi.org/10.1039/D5TA03497C.

[349] Yao Yonggang, Dong Qi, Brozena Alexandra, Luo Jian, Miao Jianwei, Chi Miaofang, Wang Chao, G Ioannis, Kevrekidis, Ren Zhiyong Jason, Greeley Jeffrey, Wang Guofeng, Anapolsky Abraham, Hu Liangbing. High-entropy nanoparticles: synthesis-structure-property relationships and data-driven discovery, Science 2022, 376, eabn3103. https://doi.org/10.1126/science.abn3103.

[350] Lu Furong, Feng Guang, Qi Huimin, Li Qichang, Su Lina, Kang Zhongyang, Hou Yuying, Huang Zhiqi, Xia Dingguo. Structurally ordered high-entropy intermetallics for electrocatalysis, Advanced Energy Materials 2025, e03306. https://doi.org/10.1002/aenm.202503306.

[351] Li Fangyi, Zhu Guihua, Jiang Jizhou, Yang Lang, Deng Fengxia, Arramel, Li Xin. A review of updated S-scheme heterojunction photocatalysts, Journal of Materials Science and Technology 2024, 177, 142-180. https://doi.org/10.1016/j.jmst.2023.08.038

[352] Shao Longfei, Lin Xi, Yang Xue, Zhao Yingyan, Zhang Jiaqi, Cheng Tao, Zou Jianxin. Magnesium-based hydrogen storage tanks: a review of research, development and simulation models, Renewable and Sustainable Energy Reviews 2025, 211, 115332. https://doi.org/10.1016/j.rser.2025.115332.

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