Ultrafast self-heating synthesis of robust heterogeneous nanocarbides for high current density hydrogen evolution reaction

A designed hierarchical porous Cu-Ni/Ni-Cu alloy converted from commercial nickel foam as versatile electrocatalysts for efficient and extremely stable water splitting

The lack of efficient and stable electrodes is a major issue hindering the wide application of alkaline water electrolysis (AWE). Here, through the designed gaseous oxidation-reduction (GOR) strategy, uniform nanopores are in-situ fabricated throughout each skeleton of commercial nickel foam (NF). Subsequently, an innovative combination of electrodeposition and a second GOR process is employed to simultaneously achieve nickel/copper alloying and the generation of more abundant nanopores. By integrating the hundred-micron pores within the skeleton of NF, a hierarchical porous Cu-Ni/Ni-Cu alloy (hp Cu-Ni/Ni-Cu) is synthesized. Three-dimensional hierarchical porous skeleton not only offers rapid electron transfer/mass transport but also provides abundant active sites with improved adsorption and desorption kinetics for reactive hydrogen intermediates. As a result, the hp Cu-Ni/Ni-Cu electrode exhibits superior alkaline HER electrocatalysis, achieving a current density of 10 mA cm-2 at a low overpotential of 31 mV. Moreover, the hp Cu-Ni/Ni-Cu-based alkaline electrolyzers also display a low voltage with 1.45 V at 20 mA cm-2 and retain excellent durability of more than 1700 h (∼2.5 months), outperforming alkaline electrolyzers composed of precious RuO2 and Pt, as well as most alkaline electrolyzers.

Atomic-Scale Confined Synthesis of Ultrathin W2C Nanowires in Single-Wall Carbon Nanotubes for the High-Performance Hydrogen Evolution Reaction

Phase-pure ultrafine W2C nanostructures are promising electrocatalysts but face synthesis challenges due to unclear formation mechanisms and harsh thermodynamics. Here, we reveal the formation mechanism of ultrathin W2C nanowires (NWs) confined in the cavity of single-wall carbon nanotubes (SWCNTs) at the atomic scale by combined in situ transmission electron microscopy and density functional theory calculations. It was found that the hollow core of SWCNTs can control the phase, axial orientation, and diameter of W2C NWs. Leveraging this mechanism, we synthesized SWCNT-encapsulated W2C NWs, WS2-W2C heterostructures, and WS2 NWs (1D@1D), which assembled into free-standing hybrid films. The integrated W2C NWs@SWCNT membrane was primarily tested, exhibiting a low overpotential of 44 mV to reach a current density of 10 mA cm-2 and outstanding durability (500 h at a high current density of 250 mA cm-2 in acidic conditions).

Ultrafast Thermal Engineering in Energy Materials: Design, Recycling, and Future Directions

Energy materials are essential for addressing global energy challenges, and their design, recycling, and performance optimization are critical for sustainable development. To efficiently rise to this occasion, advanced technology should be explored to address these challenges. This review focuses on the potential of ultrafast thermal engineering as an innovative approach to the design and recycling of energy materials and systematically examines ultrahigh temperature shock's origins, mechanisms, and developmental progress, clarifying fundamental differences between the Joule heating and carbothermal shock modes. Recent advancements in lithium/sodium battery electrode fabrication, catalyst synthesis, and battery recycling by this technology are comprehensively summarized to highlight the processing parameters, structural modulation mechanisms, and underlying principles. The review also explores the mechanisms of ultrahigh temperature shock processes, their scalability, and their environmental and economic implications. Notably, a mechanistic insight into the dynamic coexistence of Joule heating and carbothermal shock in UTS is proposed, which may synergistically govern structural evolution in poor conductivity/insulating materials. This review ultimately aims to drive the development and application of ultrafast thermal engineering in the energy materials field.

Rapid synthesis of metastable materials for electrocatalysis

Metastable materials are considered promising electrocatalysts for clean energy conversions by virtue of their structural flexibility and tunable electronic properties. However, the exploration and synthesis of metastable electrocatalysts via traditional equilibrium methods face challenges because of the requirements of high energy and precise structural control. In this regard, the rapid synthesis method (RSM), with high energy efficiency and ultra-fast heating/cooling rates, enables the production of metastable materials under non-equilibrium conditions. However, the relationship between RSM and the properties of metastable electrocatalysts remains largely unexplored. In this review, we systematically examine the unique benefits of various RSM techniques and the mechanisms governing the formation of metastable materials. Based on these insights, we establish a framework, linking RSM with the electrocatalytic performance of metastable materials. Finally, we outline the future directions of this emerging field and highlight the importance of high-throughput approaches for the autonomous screening and synthesis of optimal electrocatalysts. This review aims to provide an in-depth understanding of metastable electrocatalysts, opening up new avenues for both fundamental research and practical applications in electrocatalysis.

Synergistic Catalysts for Lithium-Sulfur Batteries: Ni Single Atom and MoC Nanoclusters Composites

The practical application of sulfur (S) cathodes in lithium-sulfur (Li-S) batteries is hindered by the shuttling of soluble lithium polysulfides (LiPSs) and sluggish sulfur redox kinetics. Addressing these challenges requires advanced catalytic host materials capable of trapping LiPSs and accelerating Li-S redox reactions. However, single-site catalysts struggle to effectively mediate the complex multi-step and multi-phase sulfur conversion processes. In this study, we present a novel dual-site catalyst, Ni-MoC-NC, featuring nickel single atoms anchored to nitrogen sites (Ni-N4) within a carbon nitride (NC) matrix and molybdenum carbide (MoC) nanoclusters. Experimental and theoretical analyses reveal that MoC sites efficiently catalyze the reduction of long-chain LiPSs (Li₂S₈ to Li₂S₄), while Ni-N4 sites drive the reduction of short-chain LiPSs (Li₂S₄ to Li₂S), resulting in a synergistic enhancement of the complete Li-S redox process. When incorporated as a coating on the cathode side of a commercial polypropylene (PP) separator, the Ni-MoC-NC catalyst enhances sulfur utilization, suppresses LiPSs shuttling, and facilitates a uniform Li+-ion distribution, effectively mitigating the uncontrolled growth of lithium dendrites. Thereby, Li-S batteries employing an S/Ni-MoC-NC cathode and a Ni-MoC-NC@PP separator demonstrate outstanding performance, including an initial capacity of 1624 mAh g⁻¹ at 0.2C and 1142 mAh g⁻¹ at 1C, retaining 590 mAh g⁻¹ after 800 cycles. At a sulfur loading of 8.3 mg cm⁻2 and an electrolyte/sulfur ratio of 6 µL mg⁻¹, the system achieves an initial areal capacity of 9.57 mAh cm⁻2 at 0.1C, showcasing significant promise for practical applications.

Interlayer Expanded MXene Film Cathodes with Rich Defects for Flexible 2-Electron Oxalate-Based Li-CO2 Batteries: A New Path to Enhanced Energy Efficiency and Durability

Aprotic Li-CO2 batteries have garnered significant attention owing to their high theoretical energy density and potential in zero-carbon technology. However, their practical application remains hindered by sluggish CO2 reduction/evolution reaction (CRR/CER) kinetics and limited flexibility. While 2D graphene-like materials are commonly employed to settle these issues, their four-electron pathway limits efficiency and reversibility. Herein, a defect-rich, interlayer-expanded Ti3C2Tx (Ex-Ti3C2Tx) film cathode is presented for flexible Li-CO2 batteries. The extended interlayer space, reduced ─OH groups, and additional uncoordinated titanium atoms of Ex-Ti3C2Tx enable abundant catalytic active sites, enhance ion and CO2 transport, and these surface functionalizations suppress interfacial oxidation. Notably, Ex-Ti3C2Tx stabilizes the bi-electron product Li2C2O4 via Ti3+/Ti2+ coupling bridges, effectively preventing disproportionation into Li2CO3, thereby significantly improving CRR/CER reversibility and lowering overpotential. Benefiting from these properties, Li-CO2 batteries with Ex-Ti3C2Tx deliver a remarkable discharge capacity of 3452.33 µAh cm-2, a low polarization potential of 0.39 V, an energy efficiency exceeding 88.9%, and an ultra-long cycling life (>1600 h). Furthermore, the belt-shaped flexible battery exhibits excellent flexibility and stable electrochemical performance under deformation highlighting its potential in wearable electronics. This work underscores the critical role of MXene-based materials in bi-electron electrocatalytic mechanisms, providing insights for advancing reversible Li-CO2 batteries and flexible energy storage technologies.

Ultrafast Synthesis of Single-Atom Catalysts for Electrocatalytic Applications

A recent development in catalytic research, single-atom catalysts (SACs) are one of the most significant categories of catalytic materials. During preparation, individual atoms migrate and agglomerate due to the high surface free energy. The rapid thermal shock strategy addresses this challenge by employing instantaneous high-temperature pulses to synthesize SACs, while minimizing heating duration to prevent metal aggregation and substrate degradation, thereby preserving atomic-level dispersion. The resultant SACs exhibit exceptional catalytic activity, remarkable selectivity, and long-term stability, which have attracted extensive attention in electrocatalysis. In this paper, cutting-edge ultrafast synthesis techniques such as Joule heating, microwave radiation, pulsed discharge, and arc discharge are comprehensively analyzed. Their ability is emphasized to achieve uniform dispersion of separated metal atoms and optimize the catalytic activity for electrocatalytic applications. A systematic summary of SACs synthesized by these rapid methods is provided, with particular emphasis on their implementation in carbon dioxide reduction reaction (CO2RR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and oxygen reduction reaction (ORR) systems. The review provides an in-depth discussion on the rapid synthesis strategy for development trend, remaining challenges, and the application prospects in electrocatalysis.

Confined Flash Pt1/WCx inside Carbon Nanotubes for Efficient and Durable Electrocatalysis

Exploiting cost-effective hydrogen evolution reaction (HER) catalysts is crucial for sustainable hydrogen production. However, currently reported nanocatalysts usually cannot simultaneously sustain high catalytic activity and long-term durability. Here, we report the efficient synthesis and activity tailoring of a chainmail catalyst, isolated platinum atom anchored tungsten carbide nanocrystals encapsulated inside carbon nanotubes (Pt1/WCx@CNTs), by confined flash Joule heating technique. The instantaneous carbothermal reduction reaction enables the millisecond formation of Pt1/WCx nanostructures from CNT-encapsulated polyoxometalates, where nanotubes serve as both heating conductors and robust chainmails. The Pt1/WCx@CNTs exhibit prominent catalytic performance toward acid HER with a low overpotential of 45.2 mV at 10 mA cm-2 and long-term durability over 500 h of continuous running. Mechanism studies reveal the strong metal-support interaction on Pt1/WCx optimizes the charge redistribution at the Pt1-W2C interface and the hydrogen adsorption/desorption behavior. This study offers a potential avenue for ultrafast and activity-controllable synthesis of highly stable single-atom catalysts.

Exploring interfacial electrocatalysis for iodine redox conversion in zinc-iodine battery

The challenges posed by the non-conductive nature of iodine, coupled with the easy formation of soluble polyiodides in water, impede its integration with zinc for the development of advanced rechargeable batteries. Here we demonstrate the in-situ loading of molybdenum carbide nanoclusters (MoC) and zinc single atoms (Zn-SA) into porous carbon fibers to invoke electrocatalytic conversion of iodine at the interface. The electronic interactions between MoC and Zn-SA lead to an upshift in the d-band center of Mo relative to the Fermi level, thus promoting the interfacial interactions with iodine species to suppress shuttle effects. Notably, the optimal charge delocalization, induced by d-p orbital hybridization between molybdenum and iodine, also lowers the redox energy barrier to promote the interfacial conversion. With interfacial electrocatalysis minimizing polyiodide intermediates via a favorable redox conversion pathway, zinc-iodine batteries therefore demonstrate a large specific capacity of 230.6 mAh g-1 and the good capacity retention for 20,000 cycles.

Rational design of precatalysts and controlled evolution of catalyst-electrolyte interface for efficient hydrogen production

The concept of precatalyst is widely accepted in electrochemical water splitting, but the role of precatalyst activation and the resulted changes of electrolyte composition is often overlooked. Here, we elucidate the impact of potential-dependent changes for both precatalyst and electrolyte using Co2Mo3O8 as a model system. Potential-dependent reconstruction of Co2Mo3O8 precatalyst results in an electrochemically stable Co(OH)2@Co2Mo3O8 catalyst and additional Mo dissolved as MoO42- into electrolyte. The Co(OH)2/Co2Mo3O8 interface accelerates the Volmer reaction and negative potentials induced Mo2O72- (from MoO42-) further enhances proton adsorption and H2 desorption. Leveraging these insights, the well-designed MoO42-/Mo2O72- modified Co(OH)2@Co2Mo3O8 catalyst achieves a Faradaic efficiency of 99.9% and a yield of 1.85 mol h-1 at -0.4 V versus reversible hydrogen electrode (RHE) for hydrogen generation. Moreover, it maintains stable over one month at approximately 100 mA cm-2, highlighting its industrial suitability. This work underscores the significance of understanding on precatalyst reconstruction and electrolyte evolution in catalyst design.

Progress and perspectives of rapid Joule heating for the preparation of highly efficient catalysts

Functional catalytic materials play an important role in environmental, biological, energy, and other fields, wherein unique properties can be endowed through various synthesis strategies. However, conventional catalyst preparation methods suffer from mild conditions, prolonged treatment and low energy transfer efficiency, thus leading to limited inherent characterisation of catalysts (such as surface oxidation and agglomeration). Recently, the rapid Joule heating method, as a novel synthesis method, has attracted widespread attention owing to its controllable kinetic conditions and eco-friendly operation, while the mechanisms, advantages and recent progress of this method have been summarized in few reviews. Herein, we systematically summarize basic fundamentals and parameters of the Joule heating technique as well as recent processes in terms of effective modification strategies based on Joule heating. Meanwhile, perspective suggestions and challenges for Joule heating methods in terms of catalytic materials are put forward. This review provides an understanding for designing advanced catalytic materials.

1D Co6Mo6C-Based Heterojunctional Nanowires from Pyrolytically "Squeezing" PMo12/ZIF-67 Cubes for Efficient Overall Water Electrolysis

The bi-transition-metal interstitial compounds (BTMICs) are promising for water electrolysis. The previous BTMICs are usually composed of irregular particles. Here, this work shows the synthesis of novel 1D Co6Mo6C-based heterojunction nanowires (1D Co/Co6Mo6C) with diameters about 50 nm and a length-to-diameter ratio about 20 for efficient water electrolysis. An interesting growth process based on pyrolytically "squeezing" PMo12 (Phosphomolybdic acid)/ZIF-67 (Zeolitic Imidazolate Framework-67) cube precursor is demonstrated. The "squeezing" growth is related to the role of Mo species for isolating Co species. A series of tests and theoretical calculation show the mutual regulation of Co and Mo to optimize the electronic structure, accelerating H2O dissociation and the reduction kinetics of H+. Additionally, the nanowires provide pathways for electron transfer and the transmission of reactants. Consequently, the 1D Co/Co6Mo6C exhibits high activity for hydrogen evolution reaction (η10 of 31 mV) and oxygen evolution reaction (η10 of 210 mV) in 1 m KOH. The electrolytic cell based on 1D Co/Co6Mo6C requires a low voltage of 1.43 V to drive 10 mA cm-2. The catalyst also exhibits good HER performance in 1 m phosphate-buffered saline solution, exceeding Pt/C at a current density >42 mA cm-2.

Hollow Mo/MoSVn Nanoreactors with Tunable Built-in Electric Fields for Sustainable Hydrogen Production

Constructing built-in electric field (BIEF) in heterojunction catalyst is an effective way to optimize adsorption/desorption of reaction intermediates, while its precise tailor to achieve efficient bifunctional electrocatalysis remains great challenge. Herein, the hollow Mo/MoSVn nanoreactors with tunable BIEFs are elaborately prepared to simultaneously promote hydrogen evolution reaction (HER) and urea oxidation reaction (UOR) for sustainable hydrogen production. The BIEF induced by sulfur vacancies can be modulated from 0.79 to 0.57 to 0.42 mV nm-1, and exhibits a parabola-shaped relationship with HER and UOR activities, the Mo/MoSV1 nanoreactor with moderate BIEF presents the best bifunctional activity. Theoretical calculations reveal that the moderate BIEF can evidently facilitate the hydrogen adsorption/desorption in the HER and the breakage of N─H bond in the UOR. The electrolyzer assembled with Mo/MoSV1 delivers a cell voltage of 1.49 V at 100 mA cm-2, which is 437 mV lower than that of traditional water electrolysis, and also presents excellent durability at 200 mA cm-2 for 200 h. Life cycle assessment indicates the HER||UOR system possesses notable superiority across various environment impact and energy consumption. This work can provide theoretical and experimental direction on the rational design of advanced materials for energy-saving and eco-friendly hydrogen production.

Arrayed metal phosphide heterostructure by Fe doping for robust overall water splitting

Transition metal phosphides (TMPs) show promise in water electrolysis due to their electronic structures, which activate hydrogen/oxygen reaction intermediates. However, TMPs face limitations in catalytic efficiency due to insufficient active sites, poor conductivity, and multiple intermediate steps in water electrolysis. Here, we synthesize a highly efficient bifunctional self-supported electrocatalyst, which consists of an N-doped carbon shell anchored on Fe-doped CoP/Co2P arrays on nickel foam (NC@Fe-CoxP/NF) using hydrothermal and phosphorization techniques. Experimental and theoretical results indicate that the modified morphology, with increased active site density and a tunable electronic structure induced by Fe doping in the CoP/Co2P heterostructure, leads to superior water electrolysis performance. The resulting NC@Fe0.1-CoP/Co2P/NF catalyst exhibits overpotentials of 122 mV for the hydrogen evolution reaction (HER) and 270 mV for the oxygen evolution reaction (OER) at 100 mA cm-2. Furthermore, using NC@Fe0.1-CoP/Co2P/NF as both the cathode and anode in an alkaline electrolyzer enables the cell system to achieve 100 mA cm-2 at a voltage of 1.70 V, while maintaining long-term catalytic durability. This work may pave the way for designing self-supported, highly efficient electrocatalysts for practical water electrolysis applications.

Roll-to-Roll Flash Joule Heating to Stabilize Electrocatalysts onto Meter-Scale Ni Foam for Advanced Water Splitting

The seamless integration of electrocatalysts onto the electrode is crucial for enhancing water electrolyzers, yet it is especially challenging when scaled up to large manufacturing. Despite thorough investigation, there are few reports that tackle this integration through roll-to-roll (R2R) methodology, a technique crucial for fulfilling industrial-scale demands. Here, we develop an R2R flash Joule heating (R2R-FJH) system to process catalytic electrodes with superior performance. The electrodes exhibited improved stability and activity, showcasing an exceptional performance within an alkaline water electrolysis (AWE) system. They achieved a low operation potential of 1.66 V at 0.5 A cm-2, coupled with outstanding durability over the operation of 800 h. We further demonstrated a prototype of a rolled-up water splitting apparatus, illustrating the efficiency of R2R-FJH electrodes in producing high-purity hydrogen through advanced water oxidation. Our study emphasized the practicality and scalability of the R2R-FJH strategy in the industrial manufacturing of high-performance electrodes for water electrolysis.

Sulfur occupancy-induced construction of ant-nest-like NiMo/CF(N) electrode for highly efficient hydrogen evolution

The microstructure of the electrocatalyst plays a critical role in the reaction efficiency and stability during electrochemical water splitting. Designing an efficient and stable electrocatalyst, further clarifying the synthesis mechanism, is still an important problem to be solved urgently. Inspired by the copper pyrometallurgy theory, an exceptionally active NiMo/CF(N) electrode, consisting of an ant-nest-like copper foam substrate (defined as CF(N)) and deposited NiMo layer, was fabricated for the alkaline hydrogen evolution reaction (HER). Our findings expounded the structure construction mechanism and highlighted the pivotal role of the spatial occupancy of sulfur atoms in the construction of the ant-nest-like structure. The NiMo/CF(N) composite, characterized by channels with a 2 μm diameter, showcases strong electronic interactions, increased catalytic active sites, enhanced electron/ion transport, and facilitated gas release during HER. Remarkably, NiMo/CF(N) demonstrates ultralow overpotentials of 21 mV to deliver a current density of 10 mA cm-2 in 1 M KOH. This electrode also exhibits outstanding durability, maintaining a current density of 200 mA cm-2 for 110 h, attributed to the chemical and structural integrity of its catalytic surface and the excellent mechanical properties of the electrode. This work advances the fundamental understanding of constructing micro/nano-structured electrocatalysts for highly efficient water splitting.

Pd@CuInP2S6 Core-Shell Nanospheres with Exceptional Hydrogen Evolution Capability and Stability in Both Alkaline and Acidic Media under Large Current Density Exceeding 1000 mA cm-2

By combining Pd with 2D layered crystal CuInP2S6 (CIPS) via laser irradiation in liquids, low-loading Pd@CIPS core-shell nanospheres are fabricated as an efficient and robust electrocatalysts for HER in both alkaline and acidic media under large current density (⩾1000 mA cm-2). Pd@CIPS core-shell nanosphere has two structural features, i) the out-shell is the nanocomposite of PdHx and PdInHx, and ii) there is a kind of dendritic structure on the surface of nanospheres, while the dendritic structure porvides good gas desorption pathway and cause the Pd@CIPS system to maintain higher HER activity and stability than that of commercial Pt/C under large current densities. Pd@CIPS exhibits very low overpotentials of -218 and -313 mV for the large current density of 1000 mA cm-2, and has a small Tafel slope of 29 and 63 mV dec-1 in 0.5 m H2SO4 and 1 m KOH condition, respectively. Meanwhile, Pd@CIPS has an excellent stability under -10 and -500 mA cm-2 current densities and 50 000 cycles cyclic voltammetry tests in 0.5 m H2SO4 and 1 m KOH, respectively, which being much superior to that of commercial Pt/C. Density functional theory (DFT) reveals that engineering electronic structure of PdHx and PdInHx nanostructure can strongly weaken the Pd─H bonding.

Engineering heterostructured Mo2C/MoS2 catalyst with hydrophilicity/aerophobicity via carbothermal shock for efficient alkaline hydrogen evolution

The exploration of high-performance hydrogen evolution reaction (HER) catalysts is conducive to the development of clean hydrogen energy, yet still remains a challenge. Herein, we rapidly synthesize the Mo2C/MoS2 heterostructure on carbon paper (Mo2C/MoS2-CP) via carbothermal shock in only two seconds. The construction of the Mo2C/MoS2 heterostructure regulates the electronic structure of the Mo site and facilitates charge transfer during the HER process. Moreover, the catalyst exhibits enhanced hydrophilicity and aerophobicity, facilitating optimal electrolyte-catalyst interaction and efficient hydrogen bubble detachment for accelerated mass transfer. Consequently, Mo2C/MoS2-CP exhibits superior intrinsic alkaline HER activity, and excellent stability for 100 h. This finding provides a novel insight into the development of outstanding HER catalysts.

Flash Joule Heating: A Promising Method for Preparing Heterostructure Catalysts to Inhibit Polysulfide Shuttling in Li-S Batteries

The "shuttle effect" issue severely hinders the practical application of lithium-sulfur (Li-S) batteries, which is primarily caused by the significant accumulation of lithium polysulfides in the electrolyte. Designing effective catalysts is highly desired for enhancing polysulfide conversion to address the above issue. Here, the one-step flash-Joule-heating route is employed to synthesize a W-W2C heterostructure on the graphene substrate (W-W2C/G) as a catalytic interlayer for this purpose. Theoretical calculations reveal that the work function difference between W (5.08 eV) and W2C (6.31 eV) induces an internal electric field at the heterostructure interface, accelerating the movement of electrons and ions, thus promoting the sulfur reduction reaction (SRR) process. The high catalytic activity is also confirmed by the reduced activation energy and suppressed polysulfide shuttling by in situ Raman analyses. With the W-W2C/G interlayer, the Li-S batteries exhibit an outstanding rate performance (665 mAh g-1 at 5.0 C) and cycle steadily with a low decay rate of 0.06% over 1000 cycles at a high rate of 3.0 C. Moreover, a high areal capacity of 10.9 mAh cm-2 (1381.4 mAh g-1) is obtained with a high area sulfur loading of 7.9 mg cm-2 but a low electrolyte/sulfur ratio of 9.0 µL mg-1.

Engineering active and robust alloy-based electrocatalyst by rapid Joule-heating toward ampere-level hydrogen evolution

Rational design of bimetallic alloy is an effective way to improve the electrocatalytic activity and stability of Mo-based cathode for ampere-level hydrogen evolution. However, it is still critical to realise desirable syntheses due to the wide reduction potentials between different metal elements and uncontrollable nucleation processes. Herein, we propose a rapid Joule heating method to effectively load RuMo alloy onto MoOx matrix. As-prepared catalyst exhibits excellent stability (2000 h @ 1000 mA cm-2) and ultralow overpotential (9 mV, 18 mV and 15 mV in 1 M KOH, 1 M PBS, 0.5 M H2SO4 solution, respectively) at 10 mA cm-2. Based on first-principle simulations and operando measurements, the impressive electrocatalytic stability and activity are investigated. And the role of rapid Joule heating method is highlighted and discussed in details. This study showcases rapid Joule heating as a feasible strategy to construct highly efficient alloy-based electrocatalysts.

Manipulating electron redistribution between iridium and Co6Mo6C bridging with a carbon layer leads to a significantly enhanced overall water splitting performance at industrial-level current density

Nowadays, alkaline water electrocatalysis is regarded as an economical and highly effective approach for large-scale hydrogen production. Highly active electrocatalysts functioning under large current density are urgently required for practical industrial applications. In this work, we present a meticulously designed methodology to anchor Ir nanoparticles on Co6Mo6C nanofibers (Co6Mo6C-Ir NFs) bridging with nitrogen-doped carbon as efficient bifunctional electrocatalysts with both excellent hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activity and stability in alkaline media. With a low Ir content of 5.9 wt%, Co6Mo6C-Ir NFs require the overpotentials of only 348 and 316 mV at 1 A cm-2 for the HER and OER, respectively, and both maintain stability for at least 500 h at ampere-level current density. Consequently, an alkaline electrolyzer based on Co6Mo6C-Ir NFs only needs a voltage of 1.5 V to drive 10 mA cm-2 and possesses excellent durability for 500 h at 1 A cm-2. Density functional theory calculations reveal that the introduction of Ir nanoparticles is pivotal for the enhanced electrocatalytic activity of Co6Mo6C-Ir NFs. The induced interfacial electron redistribution between Ir and Co6Mo6C bridging with nitrogen-doped carbon dramatically modulates the electron structure and activates inert atoms to generate more highly active sites for electrocatalysis. Moreover, the optimized electronic structure is more conducive to the balance of the adsorption and desorption energies of reaction intermediates, thus significantly promoting the HER, OER and overall water splitting performance.

Predictive Synthesis of Transition Metal Carbide via Thermochemical Oxocarbon Equilibrium

Fabricating nanoscale metal carbides is a great challenge due to them having higher Gibbs free energy of formation (ΔG°) values than other metal compounds; additionally, these carbides have harsh calcination conditions, in which metal oxidation is preferred in the atmosphere. Herein, we report oxocarbon-mediated calcination for the predictive synthesis of nanoscale metal carbides. The thermochemical oxocarbon equilibrium of CO-CO2 reactions was utilized to control the selective redox reactions in multiatomic systems of Mo-C-O, contributing to the phase-forming and structuring of Mo compounds. By harnessing the thermodynamically predicted processing window, we controlled a wide range of Mo phases (MoO2, α-MoC1-x, and β-Mo2C) and nanostructures (nanoparticle, spike, stain, and core/shell) in the Mo compounds/C nanofibers. By inducing simultaneous reactions of C-O (selective C combustion) and Mo-C (Mo carbide formation) in the nanofibers, Mo diffusion was controlled in C nanofibers, acting as a template for the nucleation and growth of Mo carbides and resulting in precise control of the phases and structures of Mo compounds. The formation mechanism of nanostructured Mo carbides was elucidated according to the CO fractions of CO-CO2 calcination. Moreover, tungsten (W) and niobium (Nb) carbides/C nanofibers have been successfully synthesized by CO-CO2 calcination. We constructed the thermodynamic map for the predictive synthesis of transition metal carbides to provide universal guideline via thermochemical oxocarbon equilibrium. We revealed that our thermochemical oxocarbon-mediated gas-solid reaction enabled the structure and phase control of nanoscale transition metal compounds to optimize the material-property relationship accordingly.

Constructing a Built-In Electric Field To Accelerate Water Dissociation for Efficient Alkaline Hydrogen Evolution

The alkaline hydrogen evolution reaction (HER) is intricately linked to the water dissociation kinetics. The quest for new strategies to accelerate this step is a pivotal aspect of enhancing the HER performance. Herein, we designed and synthesized a heterogeneous nickel phosphide/cobalt phosphide nanowire array grown on nickel foam (Ni2P/CoP/NF) to form a p-n junction structure. The built-in electric field (BEF) in the p-n junction optimizes the binding ability of hydrogen and hydroxyl intermediates, efficiently promoting water dissociation for the alkaline HER. Consequently, Ni2P/CoP/NF exhibits a lower overpotential of 58 and 118 mV at 30 and 100 mA cm-2, respectively, and high stability over 40 h at 300 mA cm-2 for the HER in 1 M KOH. Computational calculations combined with experiment results testify that the BEF presence in the p-n junction of Ni2P/CoP/NF effectively promotes water dissociation, regulates intermediate adsorption/desorption, and boosts electron transport. This study presents a rational design approach for high-performance heterogeneous electrocatalysts.

Ruthenium-Based Binary Alloy with Oxide Nanosheath for Highly Efficient and Stable Oxygen Evolution Reaction in Acidic Media

Traditional noble metal oxide, such as RuO2, is considered a benchmark catalyst for acidic oxygen evolution reaction (OER). However, its practical application is limited due to sluggish activity and severe electrochemical corrosion. In this study, Ru-Fe nanoparticles loading on carbon felt (RuFe@CF) is synthesized via an ultrafast Joule heating method as an active and durable OER catalyst in acidic conditions. Remarkably low overpotentials of 188 and 269 mV are achieved at 10 and 100 mA cm-2, respectively, with a robust stability up to 620 h at 10 mA cm-2. When used as an anode in a proton exchange membrane water electrolyzer, the catalyst shows more than 250 h of stability at a water-splitting current of 200 mA cm-2. Experimental characterizations reveal the presence of a Ru-based oxide nanosheath on the surface of the catalyst during OER tests, suggesting a surface reconstruction process that enhances the intrinsic activity and inhibits continuous metal dissolution. Moreover, density functional theory calculations demonstrate that the introduction of Fe into the RuFe@CF catalyst reduces the energy barrier and boosts its activities. This work offers an effective and universal strategy for the development of highly efficient and stable catalysts for acidic water splitting.

Heterophase Intermetallic Compounds for Electrocatalytic Hydrogen Production at Industrial-Scale Current Densities

Heterophase nanomaterials have sparked significant research interest in catalysis due to their distinctive properties arising from synergistic effects of different components and the formed phase boundary. However, challenges persist in the controlled synthesis of heterophase intermetallic compounds (IMCs), primarily due to the lattice mismatch of distinct crystal phases and the difficulty in achieving precise control of the phase transitions. Herein, orthorhombic/cubic Ru2Ge3/RuGe IMCs with engineered boundary architecture are synthesized and anchored on the reduced graphene oxide. The Ru2Ge3/RuGe IMCs exhibit excellent hydrogen evolution reaction (HER) performance with a high current density of 1000 mA cm-2 at a low overpotential of 135 mV. The presence of phase boundaries enhances charge transfer and improves the kinetics of water dissociation while optimizing the processes of hydrogen adsorption/desorption, thus boosting the HER performance. Moreover, an anion exchange membrane electrolyzer is constructed using Ru2Ge3/RuGe as the cathode electrocatalyst, which achieves a current density of 1000 mA cm-2 at a low voltage of 1.73 V, and the activity remains virtually undiminished over 500 h.

Crystalline Phase Engineering to Modulate the Interfacial Interaction of the Ruthenium/Molybdenum Carbide for Acidic Hydrogen Evolution

Ruthenium (Ru) is an ideal substitute to commercial Pt/C for the acidic hydrogen evolution reaction (HER), but it still suffers from undesirable activity due to the strong adsorption free energy of H* (ΔGH*). Herein, we propose crystalline phase engineering by loading Ru clusters on precisely prepared cubic and hexagonal molybdenum carbide (α-MoC/β-Mo2C) supports to modulate the interfacial interactions and achieve high HER activity. Advanced spectroscopies demonstrate that Ru on β-Mo2C shows a lower valence state and withdraws more electrons from the support than that of Ru on α-MoC, indicative of a strong interfacial interaction. Density functional theory reveals that the ΔGH* of Ru/β-Mo2C approaches 0 eV, illuminating an enhancement mechanism at the Ru/β-Mo2C interface. The resultant Ru/β-Mo2C exhibits an encouraging performance in a proton exchange membrane water electrolyzer with a low cell voltage (1.58 V@ 1.0 A cm-2) and long stability (500 h@ 1.0 A cm-2).

Heterojunction-Induced Rapid Transformation of Ni3+/Ni2+ Sites which Mediates Urea Oxidation for Energy-Efficient Hydrogen Production

Water electrolysis is an environmentally-friendly strategy for hydrogen production but suffers from significant energy consumption. Substituting urea oxidation reaction (UOR) with lower theoretical voltage for water oxidation reaction adopting nickel-based electrocatalysts engenders reduced energy consumption for hydrogen production. The main obstacle remains strong interaction between accumulated Ni3+ and *COO in the conventional Ni3+-catalyzing pathway. Herein, a novel Ni3+/Ni2+ mediated pathway for UOR via constructing a heterojunction of nickel metaphosphate and nickel telluride (Ni2P4O12/NiTe), which efficiently lowers the energy barrier of UOR and avoids the accumulation of Ni3+ and excessive adsorption of *COO on the electrocatalysts, is developed. As a result, Ni2P4O12/NiTe demonstrates an exceptionally low potential of 1.313 V to achieve a current density of 10 mA cm-2 toward efficient urea oxidation reaction while simultaneously showcases an overpotential of merely 24 mV at 10 mA cm-2 for hydrogen evolution reaction. Constructing urea electrolysis electrolyzer using Ni2P4O12/NiTe at both sides attains 100 mA cm-2 at a low cell voltage of 1.475 V along with excellent stability over 500 h accompanied with nearly 100% Faradic efficiency.

Design Strategies towards Advanced Hydrogen Evolution Reaction Electrocatalysts at Large Current Densities

Hydrogen (H2), produced by water electrolysis with the electricity from renewable sources, is an ideal energy carrier for achieving a carbon-neutral and sustainable society. Hydrogen evolution reaction (HER) is the cathodic half-reaction of water electrolysis, which requires active and robust electrocatalysts to reduce the energy consumption for H2 generation. Despite numerous electrocatalysts have been reported by the academia for HER, most of them were only tested under relatively small current densities for a short period, which cannot meet the requirements for industrial water electrolysis. To bridge the gap between academia and industry, it is crucial to develop highly active HER electrocatalysts which can operate at large current densities for a long time. In this review, the mechanisms of HER in acidic and alkaline electrolytes are firstly introduced. Then, design strategies towards high-performance large-current-density HER electrocatalysts from five aspects including number of active sites, intrinsic activity of each site, charge transfer, mass transfer, and stability are discussed via featured examples. Finally, our own insights about the challenges and future opportunities in this emerging field are presented.

Rationally Construction of Mn-Doped RuO2 Nanofibers for High-Activity and Stable Alkaline Ampere-Level Current Density Overall Water Splitting

Nowadays, highly active and stable alkaline bifunctional electrocatalysts toward water electrolysis that can work at high current density (≥1000 mA cm-2) are urgently needed. Herein, Mn-doped RuO2 (MnxRu1-xO2) nanofibers (NFs) are constructed to achieve this object, presenting wonderful hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performances with the overpotentials of only 269 and 461 mV at 1 A cm-2 in 1 m KOH solution, and remarkably stability under industrial demand with 1 A cm-2, significantly better than the benchmark Pt/C and commercial RuO2 electrocatalysts, respectively. More importantly, the assembled Mn0.05Ru0.95O2 NFs||Mn0.05Ru0.95O2 NFs electrolyzer toward overall water splitting reaches the current density of 10 mA cm-2 with a cell voltage of 1.52 V and also delivers an outstanding stability over 150 h of continuous operation, far surpassing commercial Pt/C||commercial RuO2, RuO2 NFs||RuO2 NFs and most previously reported exceptional electrolyzers. Theoretical calculations indicate that Mn-doping into RuO2 can significantly optimize the electronic structure and weaken the strength of O─H bond to achieve the near-zero hydrogen adsorption free energy (ΔGH*) value for HER, and can also effectively weaken the adsorption strength of intermediate O* at the relevant sites, achieving the higher OER catalytic activity, since the overlapping center of p-d orbitals is closer to the Fermi level.

High-entropy engineering with regulated defect structure and electron interaction tuning active sites for trifunctional electrocatalysis

High-entropy alloy nanoparticles (HEANs) possessing regulated defect structure and electron interaction exhibit a guideline for constructing multifunctional catalysts. However, the microstructure-activity relationship between active sites of HEANs for multifunctional electrocatalysts is rarely reported. In this work, HEANs distributed on multi-walled carbon nanotubes (HEAN/CNT) are prepared by Joule heating as an example to explain the mechanism of trifunctional electrocatalysis for oxygen reduction, oxygen evolution, and hydrogen evolution reaction. HEAN/CNT excels with unmatched stability, maintaining a 0.8V voltage window for 220 h in zinc-air batteries. Even after 20 h of water electrolysis, its performance remains undiminished, highlighting exceptional endurance and reliability. Moreover, the intrinsic characteristics of the defect structure and electron interaction for HEAN/CNT are investigated in detail. The electrocatalytic mechanism of trifunctional electrocatalysis of HEAN/CNT under different conditions is identified by in situ monitoring and theoretical calculation. Meanwhile, the electron interaction and adaptive regulation of active sites in the trifunctional electrocatalysis of HEANs were further verified by density functional theory. These findings could provide unique ideas for designing inexpensive multifunctional high-entropy electrocatalysts.

Substantial Impact of Built-in Electric Field and Electrode Potential on the Alkaline Hydrogen Evolution Reaction of Ru-CoP Urchin Arrays

Although great efforts on the delicate construction of a built-in electric field (BIEF) to modify the electronic properties of active sites have been conducted, the substantial impact of BIEF coupled with electrode potential on the electrochemical reactions has not been clearly investigated. Herein, we designed an alkaline hydrogen evolution reaction (HER) catalyst composed of heterogeneous Ru-CoP urchin arrays on carbon cloth (Ru-CoP/CC) with a strong BIEF with the guidance of density functional theory (DFT) calculations. Impressively, despite its unsatisfactory activity at 10 mA cm-2 (overpotential of 44 mV), Ru-CoP/CC exhibited better activity (357 mV) than the benchmark Pt/C catalyst (505 mV) at 1 A cm-2 . Experimental and theoretical studies revealed that strong hydrogen adsorption on the interfacial Ru atoms created a high energy barrier for hydrogen desorption and spillover, resulting in unsatisfactory activity at low current densities. However, as the electrode potential became more negative (i.e., the current density increased), the barrier for hydrogen spillover from the interfacial Ru to the Co site, which had near-zero hydrogen adsorption energy, significantly decreased, thus greatly accelerating the whole alkaline HER process. This explains why the activity of Ru-CoP is relatively susceptible to the electrode potential compared to Pt/C.

Rapid carbothermal shocking fabrication of iron-incorporated molybdenum oxide with heterogeneous spin states for enhanced overall water/seawater splitting

Molybdenum dioxide (MoO2) has been considered as a promising hydrogen evolution reaction (HER) electrocatalyst. However, the active sites are mainly located at the edges, resulting in few active sites and poor activity in the HER. Herein, we first reported on an efficient strategy to incorporate Fe into MoO2 nanosheets on Ni foam (Fe-MoO2/NF) using a rapid carbothermal shocking method (820 °C for 127 s). Notably, the different spin states between Fe and Mo atoms could lead to rich lattice dislocations in Fe-MoO2/NF, exposing abundant oxygen vacancies and the low-oxidation-state of Mo sites during the rapid Joule heating process. As tested, the catalyst exhibited superior activity with ultralow overpotentials (HER: 17 mV@10 mA cm-2; oxygen evolution reaction (OER): 310 mV@50 mA cm-2) and high OER selectivity in alkaline seawater splitting. Meanwhile, this catalyst was equipped in a home-made anion exchange membrane (AEM) seawater electrolyzer, which achieved a low energy consumption (5.5 kW h m-3). More importantly, Fe-MoO2/NF also coupled very well with a solar-driven electrolytic system and turned out a solar-to-hydrogen (STH) efficiency of 13.5%. Theoretical results also demonstrated that Fe incorporated and abundant oxygen vacancies in MoO2 can distort the distance of the Mo-O bonds and regulate the electronic structure, thus optimizing the binding energy of H*/OOH* adsorption. This method can be extended to other heterogeneous spin states in MoO2-based catalysts (e.g. Ni-MoO2/NF, Co-MoO2/NF) for seawater splitting, and provide a simple, efficient and universal strategy to prepare highly-efficient MoO2-based electrocatalysts.

A Highly Active Porous Mo2C-Mo2N Heterostructure on Carbon Nanowalls/Diamond for a High-Current Hydrogen Evolution Reaction

Developing non-precious metal-based electrocatalysts operating in high-current densities is highly demanded for the industry-level electrochemical hydrogen evolution reaction (HER). Here, we report the facile preparation of binder-free Mo2C-Mo2N heterostructures on carbon nanowalls/diamond (CNWs/D) via ultrasonic soaking followed by an annealing treatment. The experimental investigations and density functional theory calculations reveal the downshift of the d-band center caused by the heterojunction between Mo2C/Mo2N triggering highly active interfacial sites with a nearly zero ∆GH* value. Furthermore, the 3D-networked CNWs/D, as the current collector, features high electrical conductivity and large surface area, greatly boosting the electron transfer rate of HER occurring on the interfacial sites of Mo2C-Mo2N. Consequently, the self-supporting Mo2C-Mo2N@CNWs/D exhibits significantly low overpotentials of 137.8 and 194.4 mV at high current densities of 500 and 1000 mA/cm2, respectively, in an alkaline solution, which far surpass the benchmark Pt/C (228.5 and 359.3 mV) and are superior to most transition-metal-based materials. This work presents a cost-effective and high-efficiency non-precious metal-based electrocatalyst candidate for the electrochemical hydrogen production industry.

Dynamic coordination engineering of 2D PhenPtCl2 nanosheets for superior hydrogen evolution

Exploring the dynamic structural evolution of electrocatalysts during reactions represents a fundamental objective in the realm of electrocatalytic mechanism research. In pursuit of this objective, we synthesized PhenPtCl2 nanosheets, revealing a N2-Pt-Cl2 coordination structure through various characterization techniques. Remarkably, the electrocatalytic performance of these PhenPtCl2 nanosheets for hydrogen evolution reaction (HER) surpasses that of the commercial Pt/C catalyst across the entire pH range. Furthermore, our discovery of the dynamic coordination changes occurring in the N2-Pt-Cl2 active sites during the electrocatalytic process, as clarified through in situ Raman and X-ray photoelectron spectroscopy, is particularly noteworthy. These changes transition from Phen-Pt-Cl2 to Phen-Pt-Cl and ultimately to Phen-Pt. The Phen-Pt intermediate plays a pivotal role in the electrocatalytic HER, dynamically coordinating with Cl- ions in the electrolyte. Additionally, the unsaturated, two-coordinated Pt within Phen-Pt provides additional space and electrons to enhance both H+ adsorption and H2 evolution. This research illuminates the intricate dynamic coordination evolution and structural adaptability of PhenPtCl2 nanosheets, firmly establishing them as a promising candidate for efficient and tunable electrocatalysts.

An efficient cerium dioxide incorporated nickel cobalt phosphide complex as electrocatalyst for All-pH hydrogen evolution reaction and overall water splitting

Transition metal phosphides (TMPs) have been considered as potential electrocatalysts with adjustable valence states, metal characteristics, and phase diversity. However, it is necessary but remains a major challenge to obtain efficient and durable TMPs catalysts, which can realize efficiently for not only all-pH hydrogen evolution reaction (HER), but also oxygen evolution reaction (OER). Hence, cerium dioxide incorporated nickel cobalt phosphide growth on nickel foam (CeO2/NiCoP) is fabricated by hydrothermal and phosphating reaction. CeO2/NiCoP shows excellent activity for all-pH HER (overpotentials of 48, 58 and 72 mV in alkaline, neutral and acidic solution at the current density of 10 mA cm-2), and has a small OER overpotential (231 mV @ 10 mA cm-2). Moreover, the voltage of overall water splitting in alkaline solution and simulated seawater electrolyte is only 1.46 and 1.41 V (10 mA cm-2), respectively, coupled with outstanding operational stability and corrosion resistance. Further mechanism research shows that CeO2/NiCoP possesses rich heterointerfaces, which serves more exposed active sites and possesses a promising superhydrophilic and superaerophobic surface. Density functional theory calculations manifest that CeO2/NiCoP has appropriate energy for intermediates of reactions. This work provides a deep insight into the CeO2/NiCoP catalyst for high-performance water/seawater electrolysis.

Current Progress of Mo-Based Metal Organic Frameworks Derived Electrocatalysts for Hydrogen Evolution Reaction

As an important half-reaction for electrochemical water splitting, electrocatalytic hydrogen evolution reaction suffers from sluggish kinetics, and it is still urgent to search high efficiency non-platinum-based electrocatalysts. Mo-based catalysts such as Mo2 C, MoO2 , MoP, MoS2 , and MoNx have emerged as promising alternatives to Pt/C owing to their similar electronic structure with Pt and abundant reserve of Mo. On the other hand, due to the adjustable topology, porosity, and nanostructure of metal organic frameworks (MOFs), MOFs are extensively used as precursors to prepare nano-electrocatalysts. In this review, for the first time, the progress of Mo-MOFs-derived electrocatalysts for hydrogen evolution reaction is summarized. The preparation method, structures, and catalytic performance of the catalysts are illustrated based on the types of the derived electrocatalysts including Mo2 C, MoO2 , MoP, MoS2 , and MoNx . Especially, the commonly used strategies to improve catalytic performance such as heteroatoms doping, constructing heterogeneous structure, and composited with noble metal are discussed. Moreover, the opportunities and challenges in this area are proposed to guide the designment and development of Mo-based MOF derived electrocatalysts.

High-Performance Hydrogen Evolution Reaction Catalytic Electrodes by Liquid Joule-Heating Growth

Despite the great progress in the research of integrated catalytic electrodes for hydrogen evolution reaction, the efficient preparation of high-performance catalytic electrodes with high current density remains a challenging issue. In this work, a metal (Pt)-amorphous oxide (NiO) heterostructure catalyst is successfully in situ grown on nickel foam using liquid Joule-heating. Based on the superhydrophilic surface of the electrode and its superior mechanical and chemical stability, the catalytic electrode exhibits excellent catalytic performance in alkaline electrolytes with only 100 mV overpotential to achieve 5000 mA cm-2 current density and maintains a stable performance of 500 h under a fixed current density of 1000 mA cm-2 . Further verification of the practical application of the Pt@NiO-Ni electrode in the alkaline electrolyzer is conducted. The results show that the alkaline water electrolyzer with NiFe layered double hydroxide as the anode and Pt@NiO-Ni as the cathode exhibits superior performance than the previously reported electrolyzers, with a current density of 1 A cm-2 already achieved at 1.75 V, which is even comparable to some anion exchange membrane water electrolyzers. These experimental results illustrate the strong applicability of Pt@NiO-Ni electrode at industrial scale current densities.

Boosting the Hydrogen Evolution Reaction Performance of P-Doped PtTe2 Nanocages via Spontaneous Defects Formation

PtTe2 , a member of the noble metal dichalcogenides (NMDs), has aroused great interest in exploring its behavior in the hydrogen evolution reaction (HER) due to the unique type-II topological semimetallic nature. In this work, a simple template-free hydrothermal method to obtain the phosphorus-doped (P-doped) PtTe2 nanocages with abundant amorphous and crystalline interface (A/C-P-PtTe2 ) is developed. Revealed by density functional theory calculations, the atomic Te vacancies can spontaneously form on the basal planes of PtTe2 by the P doping, which results in the unsaturated Pt atoms exposed as the active sites in the amorphous layer for HER. Owing to the defective structure, the A/C-P-PtTe2 catalysts have the fast Tafel step determined kinetics in HER, which contributes to an ultralow overpotential (η = 28 mV at 10 mA cm-2 ) and a small Tafel slope of 37 mV dec-1 . More importantly, benefiting from the inner stable crystalline P-PtTe2 nanosheets, limited decay of the performance is observed after chronopotentiometry test. This work reveals the important role of the inherent relationship between structure and activity in PtTe2 for HER, which may bring another enlightenment for the design of efficient catalysts based on NMDs in the near future.

Monolithic Nickel Catalyst Featured with High-Density Crystalline Steps for Stable Hydrogen Evolution at Large Current Density

Producing hydrogen via electrochemical water splitting with minimum environmental harm can help resolve the energy crisis in a sustainable way. Here, this work fabricates the pure nickel nanopyramid arrays (NNAs) with dense high-index crystalline steps as the cata electrode via a screw dislocation-dominated growth kinetic for long-term durable and large current density hydrogen evolution reaction. Such a monolithic NNAs electrode offers an ultralow overpotential of 469 mV at a current density of 5000 mA cm-2 in 1.0 m KOH electrolyte and shows a high stability up to 7000 h at a current density of 1000 mA cm-2 , which outperforms the reported catas and even the commercial platinum cata for long-term services under high current densities. Its unique structure can substantially stabilize the high-density surface crystalline steps on the catalytic electrode, which significantly elevates the catalytic activity and durability of nickel in an alkaline medium. In a typical commercial hydrogen gas generator, the total energy conversion rate of NNAs reaches 84.5% of that of a commercial Pt/Ti cata during a 60-day test of hydrogen production. This work approach can provide insights into the development of industry-compatible long-term durable, and high-performance non-noble metal catas for various applications.

Ultrafine Electrospun Cobalt-Molybdenum Bimetallic Nitride as a Durable Electrocatalyst for Hydrogen Evolution

Transition metal nitrides are promising electrocatalysts for hydrogen evolution reaction (HER) owing to their Pt-like electronic structure. However, the harsh nitriding conditions greatly limit their large-scale applications. Herein, ultrafine Co₃Mo₃N-Mo₂C (<1 nm)-decorated carbon nanofibers (Co₃Mo₃N-Mo₂C/CNFs) were prepared by electrostatic spinning followed by pyrolysis treatment, in which the MoCo-MOF simultaneously serves as the precursor and nitrogen source. The generated synergistic interactions between Mo₂C and Co₃Mo₃N significantly adjust the electronic structure of Mo₂C and afford a fast charge transfer, which endows the resultant hybrid with superior HER electrocatalytic performances. Specifically, the as-obtained Co₃Mo₃N-Mo₂C/CNF delivers a low overpotential of only 76 mV to achieve a current density of 10 mA cm^-2 and superior durability with no obvious degradation for 200 h in acidic media. This performance outperforms most of the transition metal-based electrocatalysts reported to date. This work paves a new way for the design of catalysts with ultrasmall size and high efficiency in energy conversion.

Simple Approach for Reconciling Cyclic Voltammetry with Hydrogen Adsorption Energy for Hydrogen Evolution Exchange Current

Cyclic voltammetry (CV) is a standard technique to analyze the current-potential characteristics of the hydrogen evolution reaction (HER). Herein, we develop a computational quantum-scaled CV model for the HER building on the Butler-Volmer relation for a one-step, one-charge transfer process. Owing to a universal and absolute rate constant verified by fitting to experimental cyclic voltammograms of elemental metals, we show that the model quantifies the exchange current─the main analytical descriptor for HER activity─solely using the hydrogen adsorption free energy obtained from density functional theory calculations. Furthermore, the model resolves controversies over analytical studies for HER kinetics.

Interfacial engineering of Co5.47N/Mo5N6 nanosheets with rich active sites synergistically accelerates water dissociation kinetics for Pt-like hydrogen evolution

The development of highly efficient hydrogen evolution electrocatalysts with platinum-like activity requires precise control of active sites through interface engineering strategies. In this study, a heterostructured Co_5.47N/Mo₅N₆ catalyst (CoMoN_x) on carbon cloth (CC) was synthesized using a combination of dip-etching and vapor nitridation methods. The rough nanosheet surface of the catalyst with uniformly distributed elements exposes a large active surface area and provides abundant interface sites that serve as additional active sites. The CoMoN_x was found to exhibit exceptional hydrogen evolution reaction (HER) activity with a low overpotential of 44 mV at 10 mA cm^-2 and exceptional stability of 100 h in 1.0 M KOH. The CoMoN_x^(-)||RuO₂⁽⁺⁾ system requires only 1.81 V cell voltage to reach a current density of 200 mA cm^-2, surpassing the majority of previously reported electrolyzers. Density functional theory (DFT) calculations reveal that the strong synergy between Co_5.47N and Mo₅N₆ at the interface can significantly reduce the water dissociation energy barrier, thereby improving the kinetics of hydrogen evolution. Furthermore, the rough nanosheet architecture of the CoMoN_x catalyst with abundant interstitial spaces and multi-channels enhances charge transport and reaction intermediate transportation, synergistically improving the performance of the HER for water splitting.

Synergistic Effect of N-NiMoO4 /Ni Heterogeneous Interface with Oxygen Vacancies in N-NiMoO4 /Ni/CNTs for Superior Overall Water Splitting

The exploring of economical, high-efficiency, and stable bifunctional catalysts for hydrogen evolution and oxygen evolution reactions (HER/OER) is highly imperative for the development of electrolytic water. Herein, a 3D cross-linked carbon nanotube supported oxygen vacancy (V_o )-rich N-NiMoO₄ /Ni heterostructure bifunctional water splitting catalyst (N-NiMoO₄ /Ni/CNTs) is synthesized by hydrothermal-H₂ calcination method. Physical characterization confirms that V_o -rich N-NiMoO₄ /Ni nanoparticles with an average size of ≈19 nm are secondary aggregated on CNTs that form a hierarchical porous structure. The formation of Ni and NiMoO₄ heterojunctions modify the electronic structure of N-NiMoO₄ /Ni/CNTs. Benefiting from these properties, N-NiMoO₄ /Ni/CNTs drives an impressive HER overpotential of only 46 mV and OER overpotential of 330 mV at 10 mA cm^-2 , which also shows exceptional cycling stability, respectively. Furthermore, the as-assembled N-NiMoO₄ /Ni/CNTs||N-NiMoO₄ /Ni/CNTs electrolyzer reaches a cell voltage of 1.64 V at 10 mA cm^-2 in alkaline solution. Operando Raman analysis reveals that surface reconstruction is essential for the improved catalytic activity. Density functional theory (DFT) calculations further demonstrate that the enhanced HER/OER performance should be attributed to the synergistic effect of V_o and heteostructure that improve the conductivity of N-NiMoO₄ /Ni/CNTs and facilitatethe desorption of reaction intermediates.

Ultrafast Synthesis of Mo2C-Based Catalyst by Joule Heating towards Electrocatalytic Hydrogen Evolution Reaction

Developing earth-abundant electrocatalysts useful for hydrogen evolution reactions (HER) is critical for electrocatalytic water splitting driven by renewable energy. Molybdenum carbide (Mo2C) with the crystal structure of hexagonal symmetry has been identified to be an excellent HER catalyst due to its platinum-like electronic structure while the synthesis of Mo2C is generally time consuming and energy intensive. Herein, we demonstrated the ultrafast synthesis of a Mo2C-based electrocatalyst with Joule heating at 1473 K for only 6 s. Benefitting from several advantages including efficient catalytic kinetics, enhanced charge transport kinetics and high intrinsic activity, the as-prepared catalyst exhibited drastically enhanced HER performance compared with commercial Mo2C. It showed an overpotential of 288 mV for achieving a current density of −50 mA cm−2 and good stability, which highlighted the feasibility of the Joule heating method towards preparing efficient electrocatalysts.

Carbonization of a Molybdenum Substrate Surface and Nanoparticles by a One-Step Method of Femtosecond Laser Ablation in a Hexane Solution

Molybdenum carbides (MoC and Mo2C) are being reported for various applications, for example, catalysts for sustainable energies, nonlinear materials for laser applications, protective coatings for improving tribological performance, and so on. A one-step method for simultaneously fabricating molybdenum monocarbide (MoC) nanoparticles (NPs) and MoC surfaces with a laser-induced periodic surface structure (LIPSS) was developed by using pulsed laser ablation of a molybdenum (Mo) substrate in hexane. Spherical NPs with an average diameter of 61 nm were observed by scanning electron microscopy. The X-ray diffraction pattern and electron diffraction (ED) pattern results indicate that a face-centered cubic MoC was successfully synthesized for the NPs and on the laser-irradiated area. Notably, the ED pattern suggests that the observed NPs are nanosized single crystals, and a carbon shell was observed on the surface of MoC NPs. The X-ray diffraction pattern of both MoC NPs and LIPSS surface indicates the formation of FCC MoC, agreeing with the results of ED. The results of X-ray photoelectron spectroscopy also showed the bonding energy attributed to Mo-C, and the sp2-sp3 transition was confirmed on the LIPSS surface. The results of Raman spectroscopy have also supported the formation of MoC and amorphous carbon structures. This simple synthesis method for MoC may provide new possibilities for preparing Mo x C-based devices and nanomaterials, which may contribute to the development of catalytic, photonic, and tribological fields.

Modulating Dominant Facets of Pt through Multistep Selective Anchored on WC for Enhanced Hydrogen Evolution Catalysis

Facilitating the exposure of the active crystal facets on the surfaces of composite catalysts is a representative route to promote catalytic activity. Based on a tailored galvanic replacement reaction, herein, a self-assembly route is reported to prepare Pt-WC/CNT with Pt (200) preferential orientation and well-dispersed structure, which are capable of substantially boosting electrocatalysis in hydrogen evolution reaction (HER). Formation mechanism reveals that the (200)-dominated Pt-based catalysts form in galvanic replacement reaction through selective anchored on WC, and the multistep galvanic replacement process plays a critical role to realize the Pt (200)-dominated growth in higher Pt loading catalyst. These unique structural features endow the Pt-WC/CNT with a high turnover frequency of 94.18 H2·s-1 at 100 mV overpotential, 7-fold higher than that of commercial Pt/C (13.55 H2·s-1), ranking it among the most active catalysts. In addition, this method, which combines with gas-solid reaction and galvanic replacement reaction, paves the way to scalable synthesis as Pt facets-controllable composite catalysts to challenge commercial Pt/C.

Ultrafast materials synthesis and manufacturing techniques for emerging energy and environmental applications

Energy and environmental issues have attracted increasing attention globally, where sustainability and low-carbon emissions are seriously considered and widely accepted by government officials. In response to this situation, the development of renewable energy and environmental technologies is urgently needed to complement the usage of traditional fossil fuels. While a big part of advancement in these technologies relies on materials innovations, new materials discovery is limited by sluggish conventional materials synthesis methods, greatly hindering the advancement of related technologies. To address this issue, this review introduces and comprehensively summarizes emerging ultrafast materials synthesis methods that could synthesize materials in times as short as nanoseconds, significantly improving research efficiency. We discuss the unique advantages of these methods, followed by how they benefit individual applications for renewable energy and the environment. We also highlight the scalability of ultrafast manufacturing towards their potential industrial utilization. Finally, we provide our perspectives on challenges and opportunities for the future development of ultrafast synthesis and manufacturing technologies. We anticipate that fertile opportunities exist not only for energy and the environment but also for many other applications.