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Abstract Anion exchange membrane (AEM) water electrolysis employing non-precious metal electrocatalysts is a promising strategy for achieving sustainable hydrogen production. However, it still suffers from many challenges, including sluggish alkaline hydrogen evolution reaction (HER) kinetics, insufficient activity and limited lifetime of non-precious metal electrocatalysts for ampere-level-current-density alkaline HER. Here, we report an efficient alkaline HER strategy at industrial-level current density wherein a flexible WS2 superstructure is designed to serve as the cathode catalyst for AEM water electrolysis. The superstructure features bond-free van der Waals interaction among the low Young’s modulus nanosheets to ensure excellent mechanical flexibility, as well as a stepped edge defect structure of nanosheets to realize high catalytic activity and a favorable reaction interface micro-environment. The unique flexible WS2 superstructure can effectively withstand the impact of high-density gas-liquid exchanges and facilitate mass transfer, endowing excellent long-term durability under industrial-scale current density. An AEM electrolyser containing this catalyst at the cathode exhibits a cell voltage of 1.70 V to deliver a constant catalytic current density of 1 A cm−2 over 1000 h with a negligible decay rate of 9.67 μV h−1.

Highlights The main effects of deformation of flexible catalytic materials on the catalytic hydrogen evolution reaction performance are discussed, and a series of novel strategies to design highly active catalysts based on the mechanical flexibility of low-dimensional nanomaterials are summarized in detail. This review provides a strategic choice for the rational design of low-cost and high-performance industrialized electrocatalysts.

In recent years, there has been a surge in twistronics research, uncovering diverse emergent properties in twisted two-dimensional (2D) layered materials. Vertically stacking these materials with slight azimuthal deviation or lattice mismatch creates moiré superlattices, optimizing the structure and energy band and leading to numerous quantum phenomena with applications in electronics, optoelectronics, photonics, and twistronics. Recently, the superior (opto)electronic properties of these moiré superlattices have shown potential in catalysis, providing a platform to manipulate catalytic activity by adjusting twist angles. Despite their potential to revolutionize 2D catalysts, their application in catalysis is limited to simple reactions, and the mechanisms behind their catalytic performance remain unclear. Therefore, a comprehensive perspective on recent studies is needed to understand their catalytic effects for future research.

Hydrogen is now recognized as the primary alternative to fossil fuels due to its renewable, safe, high-energy density and environmentally friendly properties. Efficient hydrogen production through water splitting has laid the foundation for sustainable energy technologies. However, when hydrogen production is scaled up to industrial levels, operating at high current densities introduces unique challenges. It is necessary to design advanced electrocatalysts for hydrogen evolution reactions (HERs) under high current densities. This review will briefly introduce the challenges posed by high current densities on electrocatalysts, including catalytic activity, mass diffusion, and catalyst stability. In an attempt to address these issues, various electrocatalyst design strategies are summarized in detail. In the end, our insights into future challenges for efficient large-scale industrial hydrogen production from water splitting are presented. This review is expected to guide the rational design of efficient high-current density water electrolysis electrocatalysts and promote the research progress of sustainable energy.

Water splitting is widely acknowledged as an efficient method for hydrogen production. In recent years, significant research efforts have been directed towards developing cost-effective electrocatalysts. However, the management of bubbles formed on the electrode surface during electrolysis has been largely overlooked. These bubbles can impede the active sites, resulting in decreased catalytic performance and stability, especially at high current densities. Consequently, this impediment affects the energy conversion efficiency of water splitting. To address these challenges, this review offers a comprehensive overview of advanced strategies aimed at improving catalytic performance and mitigating the obstructive effects of bubbles in water splitting. These strategies primarily involve the utilization of experimental apparatus to observe bubble-growth behavior, encompassing nucleation, growth, and detachment stages. Moreover, the review examines factors influencing bubble formation, considering both mechanical behaviors and internal factors. Additionally, the design of efficient water-splitting catalysts is discussed, focusing on modifying electrode-surface characteristics. Finally, the review concludes by summarizing the potential of bubble management in large-scale industrial hydrogen production and identifying future directions for achieving efficient hydrogen production.

Electrocatalytic and photocatalytic hydrogen evolution reactions (HERs) provide a promising approach to clean energy generation. Bimetallic single-atom catalysts have been developed and explored to be advanced catalysts for HER. It is urgent to review and summarize the recent advances in developing bimetallic single-atom HER catalysts. Firstly, the fundamentals of bimetallic single-atom catalysts are presented, highlighting their unique configuration of two isolated metal atoms on their supports and resultant synergistic effects. Secondly, recent advances in bimetallic single-atom catalysts for electrocatalytic HER under acidic/alkaline conditions are then reviewed, including W-Mo, Ru-Bi, Ni-Fe, Co-Ag, and other dual-atom systems on graphene and transition metal dichalcogenides (TMDs) with enhanced HER activity versus monometallic analogs due to geometric and electronic synergies. Then, photocatalytic bimetallic single-atom catalysts on semiconducting carbon nitrides for solar H2 production are also discussed. Finally, an outlook is provided on opportunities and challenges in precisely controlling bimetallic single-atom catalyst synthesis and gaining in-depth mechanistic insights into bimetallic interactions. Further mechanistic and synthetic studies on bimetallic single-atom catalysts will be imperative for developing optimal systems for efficient and sustainable hydrogen production.

MoS2 has long been considered a promising catalyst for hydrogen production. At present, there are many strategies to further improve its catalytic performance, such as edge engineering, defect engineering, phase engineering, and so on. However, at present, there is still a great deal of controversy about the mechanism of MoS2 catalytic hydrogen production. For example, it is generally believed that the base plane of MoS2 is inert; however, it has been reported that the inert base plane can undergo a transient phase transition in the catalytic process to play the catalytic role, which is contrary to the common understanding that the catalytic activity only occurs at the edge. Therefore, it is necessary to further understand the mechanism of MoS2 catalytic hydrogen production. In this article, we summarized the latest research progress on the catalytic hydrogen production of MoS2, which is of great significance for revisiting the mechanism of MoS2 catalytic hydrogen production.

Expanding the available materials with moiré superlattices is interesting but also challenging. Here the authors use a one-step hydrothermal approach to synthesis WS2 moiré superlattices with high catalytic activity for hydrogen evolution reaction

Two-dimensional transition-metal dichalcogenides (TMDs) are considered as the next generation of hydrogen evolution electrocatalysts due to their adjustable band gap, near-zero Gibbs free energy, and lower cost compared to noble metal catalysts. However, the electrochemical catalytic hydrogen evolution performance of TMDs with two-dimensional properties is limited by innate sparse catalytic active sites, poor electrical conductivity, and weak electrical contact with the substrate. It remains challenging for the intrinsic activity of TMDs for electrocatalytic and photocatalytic hydrogen evolution reactions (HERs) to compete with the noble metal platinum. In recent years, significant development of transition metal chalcogenides, especially MoS2 and WS2, as catalysts for electrocatalytic and photocatalytic HERs has proceeded drastically. It is indispensable to summarize the research progress in this area. This review summarizes recent research results of electrocatalysts and photocatalysts for hydrogen evolution reactions based on two-dimensional materials, mainly including MoS2, WS2, and their compounds. The challenges and future development directions of two-dimensional hydrogen evolution reaction electrocatalysts and photocatalysts are summarized and prospected as well.

Photocatalysis is a potential strategy to solve energy and environmental problems. The development of new sustainable photocatalysts is a current topic in the field of photocatalysis. ZnIn2S4, a visible light-responsive photocatalyst, has attracted extensive research interest in recent years. Due to its suitable band gap, strong chemical stability, durability, and easy synthesis, it is expected to become a new hot spot in the field of photocatalysis in the near future. This mini-review presents a comprehensive summary of the modulation strategies to effectively improve the photocatalytic activity of ZnIn2S4 such as morphology and structural engineering, defects engineering, doping engineering, and heterojunction engineering. This review aims to provide reference to the proof-of-concept design of highly active ZnIn2S4-based photocatalysts for the enhanced hydrogen evolution reaction.

The in situ surface reconstitution of a catalyst for hydrogen evolution refers to its structure evolution induced by strong interactions with reaction intermediates during the hydrogen evolution reaction (HER), which eventually leads to the self-optimization of active sites. In consideration of the superior performance that can be achieved by in situ surface reconstitution, more and more attention has been paid to the relationship between active site structure evolution and the self-optimization of HER activity. More and more in situ and/or operando techniques have been explored to track the dynamic structural evolution of HER catalysts in order to clarify the underlying mechanism. This review summarizes recent advances in various types of reconstruction such as the reconfiguration of crystallinity, morphological evolution, chemical composition evolution, phase transition refactoring, surface defects, and interface refactoring in the HER process. Finally, different perspectives and outlooks are offered to guide future investigations. This review is expected to provide some new clues for a deeper understanding of in situ surface reconfiguration in hydrogen evolution reactions and the targeted design of catalysts with desirable structures.

Defects in transition metal dichalcogenides play important roles in the field of the catalytic hydrogen evolution reaction (HER). However, the use of defective MoS2 as HER catalysts remains controversial because the types of defects are various, including zero-dimensional point defects, one-dimensional linear defects, and two-dimensional plane defects. Recently, novel structures of linear defects have drawn more and more attention, and it is necessary to explore their unique properties. This review focuses on the formation mechanism, fabrication method, accurate atomic structure, and catalytic hydrogen evolution mechanism of sulfur line vacancies in MoS2 as electrocatalysts. The structure–activity relationship between line defects and catalytic performance is discussed in detail. This will provide a route for the design of excellent catalysts by engineering line defects.

While earth-abundant materials are promising catalysts for renewable energy conversion, such materials tend to display poor activities. Here, authors show FeS troilite nanosheets to undergo a near-infrared light-triggered transition to a phase that displays improved H2 evolution performances.

Abstract Efficient evolution of hydrogen through electrocatalysis holds tremendous promise for clean energy. The catalytic efficiency for hydrogen evolution reaction (HER) strongly depends on the number and activity of active sites. To this end, making vertically aligned, ultrathin, and along with rich metallic phase WS2 nanosheets is effective to maximally unearth the catalytic performance of WS2 nanosheets. Metallic 1T polymorph combined with vertically aligned ultrathin WS2 nanosheets on flat substrate is successfully prepared via one-step simple hydrothermal reaction. The nearly vertical orientation of WS2 nanosheets enables the active sites of surface edge and basal planes to be maximally exposed. Here, we report vertical 1T-WS2 nanosheets as efficient catalysts for hydrogen evolution with low overpotential of 118 mV at 10 mA cm−2 and a Tafel slope of 43 mV dec−1. In addition, the prepared WS2 nanosheets exhibit extremely high stability in acidic solution as the HER catalytic activity and show no degradation after 5000 continuous potential cycles. Our results indicate that vertical 1T-WS2 nanosheets are attractive alternative to the precious platinum benchmark catalyst and rival MoS2 materials that have recently been heavily scrutinized for hydrogen evolution. Graphical Abstract Vertical 1T-WS2 for hydrogen evolution.

Abstract The rational design and preparation of hierarchical nanoarchitectures are critical for enhanced photocatalytic hydrogen evolution reaction (HER). Herein, well-integrated hollow ZnO@TiO2 heterojunctions were obtained by a simple hydrothermal method. This unique hierarchical heterostructure not only caused multiple reflections which enhances the light absorption but also improved the lifetime and transfer of photogenerated charge carriers due to the potential difference generated on the ZnO–TiO2 interface. As a result, compared to bare ZnO and TiO2, the ZnO@TiO2 composite photocatalyst exhibited higher hydrogen production rated up to 0.152 mmol h−1 g−1 under simulated solar light. In addition, highly repeated photostability was also observed on the ZnO@TiO2 composite photocatalyst even after a continuous test for 30 h. It is expected that this low-cost, nontoxic, and readily available ZnO@TiO2 catalyst could exhibit promising potential in photocatalytic H2 to meet the future fuel needs.

Abstract Potassium‐ion batteries (KIBs) are one of the most appealing alternatives to lithium‐ion batteries, particularly attractive in large‐scale energy storage devices considering the more sufficient and lower cost supply of potassium resources in comparison with lithium. To achieve more competitive KIBs, it is necessary to search for anode materials with a high performance. Herein, the bimetallic oxide Sb2MoO6, with the presence of reduced graphene oxide, is reported as a high‐performance anode material for KIBs in this study, achieving discharge capacities as high as 402 mAh g−1 at 100 mA g−1 and 381 mAh g−1 at 200 mA g−1, and reserving a capacity of 247 mAh g−1 after 100 cycles at a current density of 500 mA g−1. Meanwhile, the potassiation/depotassiation mechanism of this material is probed in‐depth through the electrochemical characterization, operando X‐ray diffraction, transmission electron microscope, and density functional theory calculation, successfully unraveling the nature of the high‐performance anode and the functions of Sb and Mo in Sb2MoO6. More importantly, the phase development and bond breaking sequence of Sb2MoO6 are successfully identified, which is meaningful for the fundamental study of metal‐oxide based electrode materials for KIBs.

Reusing spent anodes is a pivotal step for recycling lithium-ion batteries (LIBs). However, it proves challenging to completely eliminate Cu impurities from spent graphite (SG), which hinders the effective recycling of spent anodes. In this paper, a straightforward air oxidation method is proposed to directly upgrade spent anodes into stable CuO/C anodes by harnessing the inherent Cu impurities in spent anodes. The air oxidation process not only repairs the SG to some extent but also generates uniformly dispersed CuO nanoparticles, which chemically bind with the repaired graphite (RG) through Cu–O–C bonds. The specific discharge capacity of the CuO/RG anode can reach as high as 647 mA h g−1 even after 500 cycles (at 372 mA g−1 ). In addition, this program is found to reduce energy consumption and greenhouse gas emissions by ∼80% compared to previously reported CuO/C production programs. Clearly, this approach provides a new direction for large-scale recycling of spent LIBs and low-cost production of high-performance CuO/C anodes. [ABSTRACT FROM AUTHOR]