Molybdenum disulfide (MoS₂) has garnered significant attention in the field of catalysis due to the high density of active sites in its unique two-dimensional (2D) structure, which could be developed into numerous high-performance catalysts. The synthesis of ultra-small MoS₂ particles (<10 nm) is highly desired in various experimental studies. The ultra-small structure could often lead to a distinct S–Mo coordination state and nonstoichiometric composition in MoS_x, minimizing in-plane active sites of the 2D structure and making it probable to regulate the atomic and electronic structure of its intrinsic active sites on a large extent, especially in MoS_x clusters. This article summarizes the recent progress of catalysis over ultra-small undoped MoS₂ particles for renewable fuel production. Through a systematic review of their synthesis, structural, and spectral characteristics, as well as the relationship between their catalytic performance and inherent defects, we aim to provide insights into catalysis over this matrix that may potentially enable advancement in the development of high-performance MoS₂-based catalysts for sustainable energy generation in the future.

High-entropy materials (HEMs), which are newly manufactured compounds that contain five or more metal cations, can be a platform with desired properties, including improved electrocatalytic performance owing to the inherent complexity. Here, a strain engineering methodology is proposed to design transition-metal-based HEM by Li manipulation (LiTM) with tunable lattice strain, thus tailoring the electronic structure and boosting electrocatalytic performance. As confirmed by the experiments and calculation results, tensile strain in the LiTM after Li manipulation can optimize the d-band center and increase the electrical conductivity. Accordingly, the as-prepared LiTM-25 demonstrates optimized oxygen evolution reaction and hydrogen evolution reaction activity in alkaline saline water, requiring ultralow overpotentials of 265 and 42 mV at 10 mA cm⁻², respectively. More strikingly, LiTM-25 retains 94.6% activity after 80 h of a durability test when assembled as an anion-exchange membrane water electrolyzer. Finally, in order to show the general efficacy of strain engineering, we incorporate Li into electrocatalysts with higher entropies as well.

Electrochemical C–C and C–N coupling reactions with the conversion of abundant and inexpensive small molecules, such as CO₂ and nitrogen-containing species, are considered a promising route for increasing the value of CO₂ reduction products. The development of high-performance catalysts is the key to the both electrocatalytic reactions. In this review, we present a systematic summary of the reaction systems for electrocatalytic CO₂ reduction, along with the coupling mechanisms of C–C and C–N bonds over outstanding electrocatalytic materials recently developed. The key intermediate species and reaction pathways related to the coupling as well as the catalyst-structure relationship will be also discussed, aiming to provide insights and guidance for designing efficient CO₂ reduction systems.

Solid-state supercapacitors (SSCs) are emerging as one of the promising energy storage devices due to their high safety, superior power density, and excellent cycling life. However, performance degradation and safety issues under extreme conditions are the main challenges for the practical application. With the expansion of human activities, such as space missions, polar exploration, and so on, the investigation of SSC with wide temperature tolerance, high energy density, power density, and sustainability is highly desired. In this review, the effects of temperature on SSC are systematically illustrated and clarified, including the properties of the electrolyte, ion diffusion, and reaction dynamics of the supercapacitor. Subsequently, we summarize the recent advances in wide-temperature-range SSCs from the aspect of electrolyte modification, electrode design, and interface adjustment between electrode and electrolyte, especially with critical concerns on ionic conductivity and cycling stability. In the end, a perspective is presented, expecting to promote the practical application of the SSC in harsh conditions.

For the performance optimization strategies of hard carbon, heteroatom doping is an effective way to enhance the intrinsic transfer properties of sodium ions and electrons for accelerating the reaction kinetics. However, the previous work focuses mainly on the intrinsic physicochemical property changes of the material, but little attention has been paid to the resulting interfacial regulation of the electrode surface, namely the formation of solid electrolyte interphase (SEI) film. In this work, element F, which has the highest electronegativity, was chosen as the doping source to, more effectively, tune the electronic structure of the hard carbon. The effect of F-doping on the physicochemical properties of hard carbon was not only systematically analyzed but also investigated with spectroscopy, optics, and in situ characterization techniques to further verify that appropriate F-doping plays a positive role in constructing a homogenous and inorganic-rich SEI film. The experimentally demonstrated link between the electronic structure of the electrode and the SEI film properties can reframe the doping optimization strategy as well as provide a new idea for the design of electrode materials with low reduction kinetics to the electrolyte. As a result, the optimized sample with the appropriate F-doping content exhibits the best electrochemical performance with high capacity (434.53 mA h g⁻¹ at 20 mA g⁻¹) and excellent rate capability (141 mA h g⁻¹ at 400 mA g⁻¹).

MXenes are a family of two-dimensional (2D) layered transition metal carbides/nitrides that show promising potential for energy storage applications due to their high-specific surface areas, excellent electron conductivity, good hydrophilicity, and tunable terminations. Among various types of MXenes, Ti₃C₂T_x is the most widely studied for use in capacitive energy storage applications, especially in supercapacitors (SCs). However, the stacking and oxidation of MXene sheets inevitably lead to a significant loss of electrochemically active sites. To overcome such challenges, carbon materials are frequently incorporated into MXenes to enhance their electrochemical properties. This review introduces the common strategies used for synthesizing Ti₃C₂T_x, followed by a comprehensive overview of recent developments in Ti₃C₂T_x/carbon composites as electrode materials for SCs. Ti₃C₂T_x/carbon composites are categorized based on the dimensions of carbons, including 0D carbon dots, 1D carbon nanotubes and fibers, 2D graphene, and 3D carbon materials (activated carbon, polymer-derived carbon, etc.). Finally, this review also provides a perspective on developing novel MXenes/carbon composites as electrodes for application in SCs.

The artificial photosynthesis technology has been recognized as a promising solution for CO₂ utilization. Photothermal catalysis has been proposed as a novel strategy to promote the efficiency of artificial photosynthesis by coupling both photochemistry and thermochemistry. However, strategies for maximizing the use of solar spectra with different frequencies in photothermal catalysis are urgently needed. Here, a hierarchical full-spectrum solar light utilization strategy is proposed. Based on this strategy, a Cu@hollow titanium silicalite-1 zeolite (TS-1) nanoreactor with spatially separated photo/thermal catalytic sites is designed to realize high-efficiency photothermal catalytic artificial photosynthesis. The space–time yield of alcohol products over the optimal catalyst reached 64.4 μmol g⁻¹ h⁻¹, with the selectivity of CH₃CH₂OH of 69.5%. This rationally designed hierarchical utilization strategy for solar light can be summarized as follows: (1) high-energy ultraviolet light is utilized to drive the initial and difficult CO₂ activation step on the TS-1 shell; (2) visible light can induce the localized surface plasmon resonance effect on plasmonic Cu to generate hot electrons for H₂O dissociation and subsequent reaction steps; and (3) low-energy near-infrared light is converted into heat by the simulated greenhouse effect by cavities to accelerate the carrier dynamics. This work provides some scientific and experimental bases for research on novel, highly efficient photothermal catalysts for artificial photosynthesis.

The excessive use of nonrenewable energy has brought about serious greenhouse effect. Converting CO₂ into high-value-added chemicals is undoubtedly the best choice to solve energy problems. Due to the excellent cost-effectiveness and dramatic catalytic performance, nickel-based catalysts have been considered as the most promising candidates for the electrocatalytic CO₂ reduction reaction (eCO₂RR). In this work, the electrocatalytic reduction mechanism of CO₂ over Ni-based materials is reviewed. The strategies to improve the eCO₂RR performance are emphasized. Moreover, the research on Ni-based materials for syngas generation is briefly summarized. Finally, the prospects of nickel-based materials in the eCO₂RR are provided with the hope of improving transition-metal-based electrocatalysts for eCO₂RR in the future.

Direct recycling is a novel approach to overcoming the drawbacks of conventional lithium-ion battery (LIB) recycling processes and has gained considerable attention from the academic and industrial sectors in recent years. The primary objective of directly recycling LIBs is to efficiently recover and restore the active electrode materials and other components in the solid phase while retaining electrochemical performance. This technology's advantages over traditional pyrometallurgy and hydrometallurgy are cost-effectiveness, energy efficiency, and sustainability, and it preserves the material structure and morphology and can shorten the overall recycling path. This review extensively discusses the advancements in the direct recycling of LIBs, including battery sorting, pretreatment processes, separation of cathode and anode materials, and regeneration and quality enhancement of electrode materials. It encompasses various approaches to successfully regenerate high-value electrode materials and streamlining the recovery process without compromising their electrochemical properties. Furthermore, we highlight key challenges in direct recycling when scaled from lab to industries in four perspectives: (1) battery design, (2) disassembling, (3) electrode delamination, and (4) commercialization and sustainability. Based on these challenges and changing market trends, a few strategies are discussed to aid direct recycling efforts, such as binders, electrolyte selection, and alternative battery designs; and recent transitions and technological advancements in the battery industry are presented.

Understanding the adsorption interactions between carbon materials and sulfur compounds has far-reaching impacts, in addition to their well-known important role in energy storage and conversion, such as lithium-ion batteries. In this paper, properties of intrinsic B or Si single-atom doped, and B–Si codoped graphene (GR) and graphdiyne (GDY) were investigated by using density functional theory-based calculations, in which the optimal doping configurations were explored for potential applications in adsorbing sulfur compounds. Results showed that both B or Si single-atom doping and B–Si codoping could substantially enhance the electron transport properties of GR and GDY, improving their surface activity. Notably, B and Si atoms displayed synergistic effects for the codoped configurations, where B–Si codoped GR/GDY exhibited much better performance in the adsorption of sulfur-containing chemicals than single-atom doped systems. In addition, results demonstrated that, after B–Si codoping, the adsorption energy and charge transfer amounts of GDY with sulfur compounds were much larger than those of GR, indicating that B–Si codoped GDY might be a favorable material for more effectively interacting with sulfur reagents.

Lithium–sulfur batteries (LSBs) have drawn significant attention owing to their high theoretical discharge capacity and energy density. However, the dissolution of long-chain polysulfides into the electrolyte during the charge and discharge process (“shuttle effect”) results in fast capacity fading and inferior electrochemical performance. In this study, Mn₂O₃ with an ordered mesoporous structure (OM-Mn₂O₃) was designed as a cathode host for LSBs via KIT-6 hard templating, to effectively inhibit the polysulfide shuttle effect. OM-Mn₂O₃ offers numerous pores to confine sulfur and tightly anchor the dissolved polysulfides through the combined effects of strong polar–polar interactions, polysulfides, and sulfur chain catenation. The OM-Mn₂O₃/S composite electrode delivered a discharge capacity of 561 mA h g⁻¹ after 250 cycles at 0.5 C owing to the excellent performance of OM-Mn₂O₃. Furthermore, it retained a discharge capacity of 628 mA h g⁻¹ even at a rate of 2 C, which was significantly higher than that of a pristine sulfur electrode (206 mA h g⁻¹). These findings provide a prospective strategy for designing cathode materials for high-performance LSBs.

SnO₂ has been extensively investigated as an anode material for sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) due to its high Na/K storage capacity, high abundance, and low toxicity. However, the sluggish reaction kinetics, low electronic conductivity, and large volume changes during charge and discharge hinder the practical applications of SnO₂-based electrodes for SIBs and PIBs. Engineering rational structures with fast charge/ion transfer and robust stability is important to overcoming these challenges. Herein, S-doped SnO₂ (S–SnO₂) quantum dots (QDs) (≈3 nm) encapsulated in an N, S codoped carbon fiber networks (S–SnO₂–CFN) are rationally fabricated using a sequential freeze-drying, calcination, and S-doping strategy. Experimental analysis and density functional theory calculations reveal that the integration of S–SnO₂ QDs with N, S codoped carbon fiber network remarkably decreases the adsorption energies of Na/K atoms in the interlayer of SnO₂–CFN, and the S doping can increase the conductivity of SnO₂, thereby enhancing the ion transfer kinetics. The synergistic interaction between S–SnO₂ QDs and N, S codoped carbon fiber network results in a composite with fast Na⁺/K⁺ storage and extraordinary long-term cyclability. Specifically, the S–SnO₂–CFN delivers high rate capacities of 141.0 mAh g⁻¹ at 20 A g⁻¹ in SIBs and 102.8 mAh g⁻¹ at 10 A g⁻¹ in PIBs. Impressively, it delivers ultra-stable sodium storage up to 10,000 cycles at 5 A g⁻¹ and potassium storage up to 5000 cycles at 2 A g⁻¹. This study provides insights into constructing metal oxide-based carbon fiber network structures for high-performance electrochemical energy storage and conversion devices.

Electrocatalytic water splitting seems to be an efficient strategy to deal with increasingly serious environmental problems and energy crises but still suffers from the lack of stable and efficient electrocatalysts. Designing practical electrocatalysts by introducing defect engineering, such as hybrid structure, surface vacancies, functional modification, and structural distortions, is proven to be a dependable solution for fabricating electrocatalysts with high catalytic activities, robust stability, and good practicability. This review is an overview of some relevant reports about the effects of defect engineering on the electrocatalytic water splitting performance of electrocatalysts. In detail, the types of defects, the preparation and characterization methods, and catalytic performances of electrocatalysts are presented, emphasizing the effects of the introduced defects on the electronic structures of electrocatalysts and the optimization of the intermediates' adsorption energy throughout the review. Finally, the existing challenges and personal perspectives of possible strategies for enhancing the catalytic performances of electrocatalysts are proposed. An in-depth understanding of the effects of defect engineering on the catalytic performance of electrocatalysts will light the way to design high-efficiency electrocatalysts for water splitting and other possible applications.

Metal-organic frameworks recently have been burgeoning and used as precursors to obtain various metal–nitrogen–carbon catalysts for oxygen reduction reaction (ORR). Although rarely studied, Mn–N–C is a promising catalyst for ORR due to its weak Fenton reaction activity and strong graphitization catalysis. Here, we developed a facile strategy for anchoring the atomically dispersed nitrogen-coordinated single Mn sites on carbon nanosheets (MnNCS) from an Mn-hexamine coordination framework. The atomically dispersed Mn–N₄ sites were dispersed on ultrathin carbon nanosheets with a hierarchically porous structure. The optimized MnNCS displayed an excellent ORR performance in half-cells (0.89 V vs. reversible hydrogen electrode (RHE) in base and 0.76 V vs. RHE in acid in half-wave potential) and Zn–air batteries (233 mW cm⁻² in peak power density), along with significantly enhanced stability. Density functional theory calculations further corroborated that the Mn–N₄–C₁₂ site has favorable adsorption of *OH as the rate-determining step. These findings demonstrate that the metal-hexamine coordination framework can be used as a model system for the rational design of highly active atomic metal catalysts for energy applications.

The demand for lithium-ion batteries (LIBs) is driven largely by their use in electric vehicles, which is projected to increase dramatically in the future. This great success, however, urgently calls for the efficient recycling of LIBs at the end of their life. Herein, we describe a froth flotation-based process to recycle graphite—the predominant active material for the negative electrode—from spent LIBs and investigate its reuse in newly assembled LIBs. It has been found that the structure and morphology of the recycled graphite are essentially unchanged compared to pristine commercial anode-grade graphite, and despite some minor impurities from the recycling process, the recycled graphite provides a remarkable reversible specific capacity of more than 350 mAh g⁻¹. Even more importantly, newly assembled graphite‖NMC₅₃₂ cells show excellent cycling stability with a capacity retention of 80% after 1000 cycles, that is, comparable to the performance of reference full cells comprising pristine commercial graphite.