Engineering the coordination architecture of cobalt single-atom catalysts (Co-SACs) represents a promising strategy to activate peroxymonosulfate (PMS) for sewage purification. In this study, Co single atoms were bonded to a 2,2′-bipyridine-bridged covalent heptazine framework (Bpy-CHF). The obtained Bpy-CHF-Co_0.6 catalyst contained highly homogeneous Co-N active sites and succeeded in achieving efficient generation of ¹O₂. Density functional theory (DFT) calculations showed that the Co sites tended to adsorb the terminal oxygen of PMS, which facilitated the oxidation of PMS to generate SO₅^•− and achieved efficient generation of ¹O₂, accompanied by the formation of Co(IV)=O. Furthermore, the catalyst demonstrated durability against a variety of environmental conditions, indicating potential for practical applications, and we fixed it on a PVDF microfiltration membrane to establish a continuous flow system. This study proposes innovative concepts for the advancement of catalysts that facilitate efficient and selective degradation of pollutants, as well as new insights into the selective generation of ¹O₂ and the formation of Co(IV)=O.

X-ray detection is essential in a wide range of fields, including medical diagnostics, industrial nondestructive testing, and homeland security. Among the materials used for X-ray detection, metal-free perovskites (MFPs) have recently emerged as promising class materials. They not only retain the excellent optoelectronic properties of conventional perovskites but also offer advantages typical of organic materials, such as flexibility, light weight, and chemical diversity. Importantly, MFPs are nontoxic and water degradable, with a density similar to that of human tissues, making them effective tissue-equivalent materials. Owing to these unique attributes, MFPs have garnered attention for their potential in low-cost, environmentally friendly X-ray detection technologies. In this review, we provide a comprehensive overview of MFPs, focusing on their crystal structures, compositional design, and physical characteristics. We then highlight recent advancements in their application as X-ray detectors, emphasizing material optimization, device performance, and practical implementation. Finally, we discuss the current challenges in this field and offer perspectives on future directions for MFPs as competitive materials for X-ray detection.

Aqueous zinc-halogen batteries (AZHBs) are considered as a potential contender for energy storage fields due to their inherent safety, multi-electron redox pathways, high capacity, and superior redox potentials. Although significant progress has been achieved in AZHBs, their relatively low conversion efficiency and slow kinetics have hindered their further practical application. Based on this, this review focuses on fundamental aspects of halogen conversion electrochemistry based on different redox routes to deepen systematic attention and understanding for improved AZHBs. Herein, the conversion chemistry and relative issues of AZHBs including two-electron, four-electron, and multi-electron redox routes are thoroughly summarized first. Subsequently, understanding the challenges of thermodynamics and kinetics challenges of different halogen-based cathodes of AZHBs are discussed and explored in depth. Importantly, we provide improvement strategies for constructing halogen cathodes with two-electron transfer, multi-electron transfer, and achieving synergistic effects with other redox couple. Finally, further explorations in intercalation-conversion dual-energy storage mechanisms, anode protection, and electrolyte regulations are considered as valuable directions for the future development of high-performance AZHBs.

Continuous active lithium loss in lithium-ion batteries (LIBs) systems remains a major challenge for a long calendar life, particularly the severe initial capacity loss of high-capacity anode materials. In response to this critical issue, lithium replenishment technologies, encompassing both pre-lithiation and continuous lithium compensation strategies, have emerged as focal points of intensive research. This review provides a comprehensive and critical summary of recent advancements in these areas. The discussion commences with an in-depth analysis of mechanisms underlying active lithium loss associated with anode materials including graphite and other high capacity materials. A variety of pre-lithiation strategies, involving both anode-side and cathode-side techniques, are systematically categorized, compared, and evaluated in terms of their effectiveness, limitations, and implementation challenges. This work represents the systematic compilation and analysis of contemporary continuous lithium compensation strategies, highlighting their potential as innovative and promising solutions to mitigate lithium loss throughout the entire lifespan of LIBs.

Flexible supercapacitors based on hydrogels have developed rapidly, although they still face issues such as low voltage window and easy freezing of gel at low temperatures. Herein, the biological zwitterionic betaine is utilized to lock water molecular for widening the voltage window and improving anti-freezing performances of PAM/PEG/CS/Betaine-composited hydrogels (named as PPCBx, x denotes the amount of betaine). By optimizing the betaine contents, the PPCB_0.03 hydrogel reaches the stress limit of 102.04 KPa at the tensile strain limit of 400%, with a high ionic conductivity of 2.87 S m⁻¹. The ionic conductivity remains at 0.45 and 0.15 S m⁻¹ even at −30 and −50°C. The assembled supercapacitor can endow a high voltage window reaching 2.4 V. The specific area capacity of the device is 585.45 mF cm⁻² at the current density of 2 mA cm⁻² and maintains 82% after 9000 cycles. The specific capacity can still remain 191.24 mF cm⁻² even at −50°C, demonstrating its remarkable anti-freezing feature. Assembled with solar cells, the device can be successfully utilized for energy harvesting.

The rapid advancement in wearable, portable, and foldable electronic devices has underscored inherent deficiencies in conventional energy storage technologies, particularly with respect to mechanical compliance and device miniaturization. Overcoming these limitations demands energy storage solutions that integrate high electrochemical performance with mechanical resilience and scalability. In this context, MXenes, two-dimensional (2D) transition metal carbides, nitrides, or carbonitrides, have emerged as promising candidates due to their outstanding electrical conductivity, tunable surface chemistry, and intrinsic flexibility. Unlike previous reviews that focus primarily on MXene synthesis or individual device performance, this work provides a synergistic and cross-disciplinary perspective on the structural design of MXene architectures for flexible energy storage systems. It critically correlates hierarchical structural engineering (such as composite integration, dimensional hybridization, and interface modulation) with the mechanical and electrochemical behaviors of MXenes in various device configurations, including flexible batteries and supercapacitors (SCs). Particular attention is given to mechanical-electrochemical coupling mechanisms that govern flexibility retention, strain accommodation, and charge transport dynamics. Furthermore, this review offers a comparative discussion across multiple chemistries, encompassing Li-, Na-, Zn-, and K-ion batteries and SCs, thereby providing an integrative understanding of MXene functionality beyond single-system studies. Finally, this review outlines emerging design principles, fabrication strategies, and research directions aimed at achieving scalable, durable, and high-performance MXene-based flexible energy storage technologies. This synergistic perspective bridges the gap between mechanical engineering and electrochemical optimization, offering new insights for the next generation of flexible and wearable power systems.

With the intensification of the global energy and environmental crises, organic phase change energy storage materials (OPCM) are widely used in energy efficient buildings. However, conventional OPCM are easily flammable and prone to leak, which restricts their applications in emerging fields. Herein, a novel intrinsic flame retardant OPCM (bis (polyethylene glycol) methyl phosphonate, BPMP) was successfully synthesized by the nucleophilic substitution reaction of polyethylene glycol (PEG) and methyl phosphorus dichloride. Compared with conventional OPCM, BPMP is almost incapable of being ignited and maintains a phase change latent heat (153.57 J/g) similar to that of PEG. Subsequently, flame-retardant energy-storage transparent wood (FOPTW) was prepared by vacuum pressure impregnation of BPMP into the delignified cellulose frame. Due to the capillary action and intermolecular hydrogen bonding of wood stencil, FOPTW exhibited excellent leak resistance and reinforcement properties. The enthalpy of FOPTW was up to 77.23 J/g with only minor changes after 50 cycles. Meanwhile, FOPTW can realize the immediate extinguishment effect from fire, and its rate and total amount of heat release are 17% and 50.7% lower than those of OPTW. It is attributed to the gas-phase radical trapping and condensed-phase catalytic charring effect of BPMP in FOPTW. Meanwhile, the phase transition latent heat process of FOPTW is used to embed temperature sensors inside it and construct thermal runaway warning devices, thus realizing active and repetitive high temperature warnings for OPCM. This bio-based energy storage material with multiple fire safety protection systems provides a novel design idea for creating intelligent, green, and safe buildings in the 21st century.

Solar-driven CO₂ reduction faces major limitations due to insufficient photoabsorption, delayed electron-hole separation, and a significant CO₂ activation barrier. Defect engineering was used to optimize these vital processes. As a prototype, typical nontoxic ternary sulfide CaIn₂S₄ (CIS) nanoflowers were designed, and abundant sulfur vacancies were deliberately created on their surfaces. The charge delocalization around the sulfur vacancies contributes to CO₂ conversion into the *COOH intermediate, which was confirmed by in situ Fourier-transform infrared spectroscopy. Ultrafast transient absorption spectroscopy manifests the sulfur vacancy that allows for a ∼1.3-fold increase in average recovery lifetime, confirmed by photoelectrochemical analysis and DFT calculations, which ensure promoted carrier separation rates. Consequently, the CISv demonstrates a CO rate of 10.95 μmol g⁻¹ h⁻¹, which is about 6.5 times greater than the pristine CIS nanoflowers, and its photocatalytic activity remains almost unchanged after 120 h of photocatalysis. Our findings will stimulate further research on vacancy-containing catalyst design for CO₂ reduction to hydrocarbons.

The regulation of oxygen vacancies in metal oxide matrices is crucial for achieving efficient supported catalysts, albeit posing significant challenges. In this work, we propose a facile thermal shock method as an alternative to the conventional prolonged calcination process for synthesizing highly dispersed Pt nanoparticles supported on a TiO₂ substrate with abundant oxygen vacancies (referred to as Pt@O_v-TiO₂), which is achieved by utilizing a movable hot bed that shuttled between a high temperature heating zone and a liquid nitrogen cooling zone. A sudden heating-to-cooling pyrolytic conversion process spanning not only endows substrates with abundant oxygen vacancies but also yields small and well-dispersed noble metal nanoparticles. The Pt@O_v–TiO₂ catalyst demonstrates exceptional electrocatalytic hydrogen evolution reaction (HER) performance in acidic media, achieving a current density of 10 mA cm⁻² at a low potential of 39.9 mV. Furthermore, it exhibits superior mass activity and remarkable stability compared to commercial Pt/C catalysts. Density functional theory (DFT) calculations demonstrate the introduction of oxygen vacancies contributes to a stronger interaction between TiO₂ substrate and Pt, optimizing the free energy of hydrogen adsorption on the electron-rich Pt species, thereby enhancing the electrocatalytic HER performance. This finding provides a pathway for understanding the synergistic modulation of support defects and noble metal particles, thereby optimizing the interaction between the support and metal in substrate-supported metal electrocatalysts for highly efficient hydrogen production.

Molten salt synthesis has emerged as a versatile platform for the structural engineering of electrocatalysts, offering distinct advantages in controlling phase composition, morphology, and defect chemistry under thermodynamically and kinetically favorable conditions. However, critical challenges remain in elucidating the underlying mechanisms of molten salt-mediated transformations, particularly regarding the influence of salt composition, redox activity, and thermal behavior on structural evolution and catalytic properties. This review provides a materials-centered analysis of molten salt synthesis, emphasizing its structural modulation capabilities relative to conventional approaches. It systematically discusses six major classes of electrocatalysts: carbon-based materials, metals and alloys, metal oxides, metal carbides and nitrides, metal sulfides and phosphides, and hybrid composites. The unique advantages of molten salt environments are highlighted in enabling controlled nanoscale architecture, tunable porosity, precise crystallographic orientation, and effective surface/interface engineering. These features facilitate the formation of metastable phases, high-index facets, hierarchical porosity, and active defect sites, collectively enhancing charge transfer, active site exposure, and durability of catalysts. By correlating molten salt-induced structural features with improved performance in water splitting, oxygen reduction, and carbon dioxide reduction, this review establishes a unified framework for catalyst design and offers mechanistic insights to guide future development of high-efficiency electrocatalysts via molten salt strategies.

Achieving sustainable energy generation without causing environmental pollution is one of modern society's grand challenges. Photocatalytic overall water splitting (OWS) presents a sustainable option for producing the green energy vector H₂ while eliminating the need for sacrificial agents. However, the selection of appropriate catalysts is essential for the practical viability of this approach. Among various photocatalytic materials, layered perovskites have attracted significant attention due to their compositional flexibility and attractive hybrid electronic band structure. Moreover, their intrinsic layered architecture promotes charge separation, which further enhances photocatalytic performance. Therefore, layered perovskites are considered promising candidates for photocatalytic OWS. Herein, this review classifies and summarizes the research progress of (100)-, (110)-, and (111)-type layered perovskite photocatalysts for OWS. We first introduce the basic principle of photocatalytic OWS, followed by a discussion of the advantages and challenges of employing layered perovskites as OWS photocatalysts. The relevant properties of layered perovskite photocatalysts that influence OWS performance are analyzed. Furthermore, experimental strategies such as doping, composite structure construction, and morphology modulation are comprehensively reviewed to highlight their roles in enhancing photocatalytic efficiency. Finally, current limitations and future research directions for layered perovskite-based OWS are outlined to guide further developments in this field.

The traditional noble metal and transition metal catalysts encounter challenges due to the high cost and potential environmental pollution in the electrocatalytic 5-hydroxymethylfurfural oxidation reaction (HMFOR). The construction of the Co-N bond not only can reduce the excessive use of metals but also effectively enhances the electrocatalytic performance by increasing the electron transfer rate and promoting the adsorption of key intermediates. In this work, low-content Co-modified carbon nitride (CN) with a Co-N bond (1% Co-CN/NF) was constructed as an electrocatalytic catalyst for HMFOR, and excellent FDCA production yield could be achieved in both low-concentration (10 mM) and high-concentration HMF (100 mM). In situ/ex situ characterization combined with DFT calculation confirmed that the formation of the Co-N bond enhanced the electron transport rate during the HMFOR process, reduced the adsorption potential of HMF on the electrode, and promoted the adsorption of HMF; thus, the HMFOR performance was effectively improved. Subsequently, based on its potential application prospects, the experimental conditions were optimized by the XGBoost model of machine learning (ML) to achieve obvious performance improvement (achieving 100% of HMF conversion, 99.04% of FDCA yield, 98.86% of FE, and 24 cycles of stability) in 10 mM HMF, and the results were higher than those of currently reported organic electrocatalysts and even most Co-based electrocatalysts. It was exciting that superior FDCA productivity yield and recovery yield were obtained in a photovoltaic electrocatalysis (PVEC) system with 100 mM HMF. This work is expected to provide precise and detailed insights into the further construction of a novel low-budget, environmentally friendly, efficient, and stable HMFOR system.

The development of efficient, stable, and earth-abundant electrocatalysts is critical for advancing electrochemical water splitting as a sustainable hydrogen production technology. Among non-precious candidates, cobalt-based materials have garnered significant attention due to their structural versatility and tunable electronic properties. This review comprehensively examines recent progress in cobalt-based catalysts for the hydrogen and oxygen evolution reactions. We discuss key optimization strategies, including nanostructuring, heteroatom doping, and defect/interface engineering, that enhance activity and stability by increasing active site density, improving conductivity, and optimizing intermediate adsorption energetics. A particular focus is placed on the dynamic reconstruction of pre-catalysts into active (oxy)hydroxide phases under operational conditions, a crucial consideration for rational design. By integrating mechanistic insights from advanced in situ characterization and theoretical calculations, we elucidate structure-activity relationships and reaction pathways. Finally, we outline persistent challenges and future directions, emphasizing the need for standardized evaluation and the design of durable catalysts capable of operating at industrial-scale current densities to bridge the gap between laboratory research and practical application.

As the global energy shortage challenge and transition continues, greater attention is being drawn to natural hydrogen, a clean and high-potential energy source. This review aims to provide an overview about the formation mechanism, exploration technology, research status of revolutionary natural hydrogen, as well as its key role and potential impact in achieving a sustainable future for energy. Natural hydrogen is produced primarily through serpentinization, a process in which water reacts with iron-rich ultrabasic rocks and is hypothesized to have the potential for forming gas accumulations in certain suitable regions of the world. Although natural hydrogen reserves are presently unclear, it is a promising solution to accelerate the decarbonization of energy-intensive industries. Until now, numerous studies have been conducted in many countries and regions, leading to multiple ambitious projects (currently under construction or implementation) and demonstrating the feasibility of using existing technologies for the safe exploration of natural hydrogen. With the development of natural hydrogen, it is believed that more resources will be certainly found and the remaining issues could be resolved in the future. This work could offer important insights for the development of natural hydrogen that is a key toward a sustainable future of energy.