High-Performance Hydrogen Evolution Electrocatalyst Derived from Ni3C Nanoparticles Embedded in a Porous Carbon Network

Nickel Carbide Nanoparticle Catalyst for Selective Hydrogenation of Nitriles to Primary Amines

Despite its unique physicochemical properties, the catalytic application of nickel carbide (Ni3 C) in organic synthesis is rare. In this study, we report well-defined nanocrystalline Ni3 C (nano-Ni3 C) as a highly active catalyst for the selective hydrogenation of nitriles to primary amines. The activity of the aluminum-oxide-supported nano-Ni3 C (nano-Ni3 C/Al2 O3 ) catalyst surpasses that of Ni nanoparticles. Various aromatic and aliphatic nitriles and dinitriles were successfully converted to the corresponding primary amines under mild conditions (1 bar H2 pressure). Furthermore, the nano-Ni3 C/Al2 O3 catalyst was reusable and applicable to gram-scale experiments. Density functional theory calculations suggest the formation of polar hydrogen species on the nano-Ni3 C surface, which were attributed to the high activity of nano-Ni3 C towards nitrile hydrogenation. This study demonstrates the utility of metal carbides as a new class of catalysts for liquid-phase organic reactions.

Electronic interaction of ruthenium species on bimetallic phosphide for superior electrocatalytic hydrogen generation

The exploitation of high-performance electrocatalysts to achieve the economic electrocatalytic hydrogen evolution reaction (HER) is significant in generating H2 fuel. Enhancing the activity of the carrier catalyst by modifying trace precious metals is one of the important strategies. Herein, a hybrid material is developed by incorporating trace Ru species into a bimetallic phosphide (NiCoP) matrix on nickel foam (NF), showing a superior catalytic activity for HER. The Ru-NiCoP/NF hybrid material has plenty of heterointerfaces, improved electronic interaction, and small interfacial charge transfer resistance, improving the reaction kinetics of the HER. Remarkable, the Ru-NiCoP/NF provides a low overpotential of 96 mV at the current density of 50 mA cm-2 and high stability in 1.0 M KOH solution presenting a promising potential for hydrogen production. In addition, the Ru-NiCoP/NF sample exhibits the highest TOF value of 0.54 s-1 at an overpotential of 100 mV, which outperforms the commercial Ru/C catalyst. This study offers a promising approach for the synthesis of other precious metal supported hybrid materials.

Oxygen-Bridged Stabilization of Single Atomic W on Rh Metallenes for Robust and Efficient pH-Universal Hydrogen Evolution

Highly efficient and durable electrocatalysts are of the utmost importance for the sustainable generation of clean hydrogen by water electrolysis. Here, we present a report of an atomically thin rhodium metallene incorporated with oxygen-bridged single atomic tungsten (Rh-O-W) as a high-performance electrocatalyst for pH-universal hydrogen evolution reaction. The Rh-O-W metallene delivers ascendant electrocatalytic HER performance, characterized by exceptionally low overpotentials, ultrahigh mass activities, excellent turnover frequencies, and robust stability with negligible deactivation, in pH-universal electrolytes, outperforming that of benchmark Pt/C, Rh/C and numerous other reported precious-metal HER catalysts. Interestingly, the promoting feature of -O-W single atomic sites is understood via operando X-ray absorption spectroscopy characterization and theoretical calculations. On account of electron transfer and equilibration processes take place between the binary components of Rh-O-W metallenes, fine-tuning of the density of states and electron localization at Rh active sites is attained, hence promoting HER via a near-optimal hydrogen adsorption.

Interfacial Electronic Rearrangement and Synergistic Catalysis for Alkaline Water Splitting in Carbon-Encapsulated Ni (111)/Ni3C (113) Heterostructures

The realization of efficient water electrolysis is still blocked by the requirement for a high and stable driving potential above thermodynamic requirements. An Ni-based electrocatalyst, is a promising alternative for noble-metal-free electrocatalysts but tuning its surface electronic structure and exposing more active sites are the critical challenges to improving its intrinsic catalytic activity. Here, we tackle the challenge by tuning surface electronic structures synergistically with interfacial chemistry and crystal facet engineering, successfully designing and synthesizing the carbon-encapsulated Ni (111)/Ni3C (113) heterojunction electrocatalyst, demonstrating superior hydrogen evolution reaction (HER) activities, good stabilities with a small overpotential of −29 mV at 10 mA/cm2, and a low Tafel slope of 59.96 mV/dec in alkaline surroundings, approximating a commercial Pt/C catalyst and outperforming other reported Ni-based catalysts. The heterostructure electrocatalyst operates at 1.55 V and 1.26 V to reach 10 and 1 mA cm−2 in two-electrode measurements for overall alkaline water splitting, corresponding to 79% and 98% electricity-to-fuel conversion efficiency with respect to the lower heating value of hydrogen.

Sodium Hexa-Titanate Nanowires Modified with Cobalt Hydroxide Quantum Dots as an Efficient and Cost-Effective Electrocatalyst for Hydrogen Evolution in Alkaline Media

A novel electrocatalyst with high activity and enhanced durability toward the hydrogen evolution reaction (HER) in alkaline media has been designed and fabricated based on sodium hexa-titanate (Na₂Ti₆O₁₃) nanowires synthesized by a hydrothermal process and modified with Co(OH)₂ quantum dots (QDs) by a facile chemical bath deposition (CBD) method. The current response of the developed Ti/Na₂Ti₆O₁₃/Co(OH)₂ nanocomposite electrode attained 10 mA cm^-2 at an overpotential of 159 mV. The nanocomposite electrode exhibited a high stability at an applied current of 100 mA cm^-2. The remarkable catalytic behavior was achieved with a loading amount of ca. 0.06 mg cm^-2 cobalt hydroxide. This is attributed to the high electrochemically active surface area (EASA) gained by the nanowire-structured substrate and considerable enhancement of electrochemical conductivity with the use of Co(OH)₂ quantum dots as an active material. The superior catalytic activity and high stability show that the developed catalyst is a promising candidate for hydrogen production in alkaline media.

A Single Source, Scalable Route for Direct Isolation of Earth-Abundant Nanometal Carbide Water-Splitting Electrocatalysts

Single-phase M_xCs (M = Fe, Co, and Ni) were prepared by solvothermal conversion of Prussian blue single source precursors. The single source precursor is prepared in water, and the conversion process is carried out in alkylamines at reaction temperatures above 200 °C. The reaction is scalable using a commercial source of Fe-PB. High-resolution transmission electron microscopy, X-ray photoelectron microscopy, and powder X-ray diffraction confirm that carbides have thin oxide termination but lack graphitic surfaces. Electrocatalytic activity reveals that Fe₃C and Co₂C are oxygen evolution reaction electrocatalysts, while Ni₃C is a bifunctional [OER and hydrogen evolution reaction (HER)] electrocatalyst.

Non-Covalent Functionalization of Graphene Oxide-Supported 2-Picolyamine-Based Zinc(II) Complexes as Novel Electrocatalysts for Hydrogen Production

Three mononuclear 2-picolylamine-containing zinc(III) complexes viz [(2-PA)2ZnCl]2(ZnCl4)] (Zn1), [(2-PA)2Zn(H2O)](NO3)2] (Zn2) and [Zn(2-PA)2(OH)]NO3] (Zn3) were synthesized and fully characterized. Spectral and X-ray structural characteristics showed that the Zn1 complex has a square-pyramidal coordination environment around a zinc(II) core. The hydroxide complex Zn3 was non-covalently functionalized with few layers of graphene oxide (GO) sheets, formed by exfoliation of GO in water. The resulting Zn3/GO hybrid material was characterized by FT-IR, TGA-DSC, SEM-EDX and X-ray powder diffraction. The way of interaction of Zn3 with GO has been established through density functional theory (DFT) calculations. Both experimental and theoretical findings indicate that, on the surface of GO, the complex Zn3 forms a complete double-sided adsorption layer. Zn3 and its hybrid form Zn3/GO have been individually investigated as electrocatalysts for the hydrogen evolution reaction. The hybrid heterogenized form Zn3/GO was supported on glassy carbon (GC) with variable loading densities of Zn3 (0.2, 0.4 and 0.8 mg cm−2) to form electrodes. These electrodes have been tested as molecular electrocatalysts for the hydrogen evolution reaction (HER) using linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) in 0.1 M KOH. Results showed that both GC-Zn3 and GC-Zn3/GO catalysts for the HER are highly active, and with increase of the catalyst’s loading density, this catalytic activity enhances. The high catalytic activity of HER with a low onset potential of −140 mV vs. RHE and a high exchange current density of 0.22 mA cm−2 is achieved with the highest loading density of Zn3 (0.8 mg cm−2). To achieve a current density of 10 mA cm−2, an overpotential of 240 mV was needed.

Nickel carbide (Ni3C) nanoparticles for catalytic hydrogenation of model compounds in solvent

Nickel carbide nanoparticles (Ni3C) synthesized in high-boiling point solvent are used as colloidal catalysts for the hydrogenation of polar groups and hydrocarbons. They are stable under operating conditions (100 °C, 7 bar H2).

Construction of Z-scheme NiO/NiC/g-C3N4 composites using NiC as novel cocatalysts for the efficient photocatalytic degradation

A novel composite consisting of NiO/NiC/g-C₃N₄ with excellent photocatalytic properties was successfully synthesized by the simple calcination of layered double metal hydroxide (LDH) and melamine. The color and chemical composition of the as-prepared composites could be tailored by changing the mass ratio of NiAl-LDH and g-C₃N₄. For the L4C composite at the ratio of 1 : 1, it showed the desired dark color due to the generated NiC. It also showed high photodegradation efficiency under visible light irradiation, reaching 97.5% toward Rhodamine B and 92.6% toward tetracycline. The high photodegradation efficiency could be mainly attributed to the unique formation of NiC cocatalysts coupled with g-C₃N₄ and NiO semiconductors, which constructed a Z-scheme system and facilitated the efficient separation of the photogenerated electron–hole pairs. The present findings provide a promising approach for fabricating the new types of composite photocatalysts for pollutant degradation.

A novel composite consisting of NiO/NiC/g-C₃N₄ with excellent photocatalytic properties was successfully synthesized by the simple calcination of layered double metal hydroxide (LDH) and melamine.

Transition metal nitrides for electrochemical energy applications

This review comprehensively summarizes the progress on the structural and electronic modulation of transition metal nitrides for electrochemical energy applications.

NiO-decorated graphitic carbon nitride toward electrocatalytic hydrogen production from ethanol

In this study, exfoliated g-C3N4/NiO nanocomposites were synthesized by the heat treatment of urea and subsequent ultrasonic exfoliation of the colloidal solution with the introduction of nickel acetate. Ultrafine nanocomposites were obtained after repeated heat treatment and were marked as initial g-C3N4, g-C3N4/NiO 2.5%, g-C3N4/NiO 5.0%, g-C3N4/NiO 7.5%, and g-C3N4/NiO 10%. The successful attachment of NiO to the surface of g-C3N4 was further confirmed by the results of TEM and SAED. The average sizes of the coherent scattering region, determined by the broadening of the reflex (002), were 11.6, 10.4, 10.4, 9.9 and 9.9 nm for the initial, 2.5%, 5.0%, 7.5%, 10% samples, respectively. The obtained powder of graphite-like carbon nitride and the NiO-composites, according to the results of low-temperature nitrogen adsorption, had a mesoporous structure and was characterized by an average pore size of 16.6-20.8 nm and a porosity of 0.40-0.57 cm3 g-1. It was found that increasing the amount of nickel oxide in the composite had a positive effect on the electrochemical characteristics of the electrode during electro-catalytic reforming - hydrogen evolution from a water-alcohol solution. The g-C3N4/NiO 7.5% nanocomposite showed the best results. Based on voltammetry, it was found that the overpotential of the hydrogen evolution reaction on graphitic carbon nitride equalled 215 mV (at 10 mA cm-2) and the Tafel slope was 95 mV dec-1. The results of the cyclic voltammetry of the electrode based on exfoliated g-C3N4 indicated its high stability.

Synergistic Coupling of Ni Nanoparticles with Ni3 C Nanosheets for Highly Efficient Overall Water Splitting

Exploring earth-abundant bifunctional electrocatalysts with high efficiency for water electrolysis is extremely demanding and challenging. Herein, density functional theory (DFT) predictions reveal that coupling Ni with Ni₃ C can not only facilitate the oxygen evolution reaction (OER) kinetics, but also optimize the hydrogen adsorption and water adsorption energies. Experimentally, a facile strategy is designed to in situ fabricate Ni₃ C nanosheets on carbon cloth (CC), and simultaneously couple with Ni nanoparticles, resulting in the formation of an integrated heterostructure catalyst (Ni-Ni₃ C/CC). Benefiting from the superior intrinsic activity as well as the abundant active sites, the Ni-Ni₃ C/CC electrode demonstrates excellent bifunctional electrocatalytic activities toward the OER and hydrogen evolution reaction (HER), which are superior to all the documented Ni₃ C-based electrocatalysts in alkaline electrolytes. Specifically, the Ni-Ni₃ C/CC catalyst exhibits the low overpotentials of only 299 mV at the current density of 20 mA cm^-2 for the OER and 98 mV at 10 mA cm^-2 for the HER in 1 m KOH. Furthermore, the bifunctional Ni-Ni₃ C/CC catalyst can propel water electrolysis with excellent activity and nearly 100% faradic efficiency. This work highlights an easy approach for designing and constructing advanced nickel carbide-based catalysts with high activity based on the theoretical predictions.

Amorphous RuS2 electrocatalyst with optimized active sites for hydrogen evolution

Transition metal chalcogenides have attracted much attention as high-performance electrocatalysts for hydrogen evolution reaction (HER). Here, we synthesized an efficient HER electrocatalyst of amorphous ruthenium sulfide (A-RuS₂), exhibiting an overpotential of 141 mV at the current density of 10 mA cm^-2 and a Tafel slope of 65.6 mV dec^-1. Experiments demonstrate amorphous RuS₂ has much better catalytic activity than that of its crystalline counterparts. Our study shows that amorphous RuS₂ has increased intrinsic activity and active sites. This work provides a feasible strategy for the development of HER electrocatalysts in amorphous state.

Nitrogen-Doped Graphene-Encapsulated Nickel-Copper Alloy Nanoflower for Highly Efficient Electrochemical Hydrogen Evolution Reaction

Development of high-performance and low-cost nonprecious metal electrocatalysts is critical for eco-friendly hydrogen production through electrolysis. Herein, a novel nanoflower-like electrocatalyst comprising few-layer nitrogen-doped graphene-encapsulated nickel-copper alloy directly on a porous nitrogen-doped graphic carbon framework (denoted as Ni_x Cu_y @ NG-NC) is successfully synthesized using a facile and scalable method through calcinating the carbon, copper, and nickel hydroxy carbonate composite under inert atmosphere. The introduction of Cu can effectively modulate the morphologies and hydrogen evolution reaction (HER) performance. Moreover, the calcination temperature is an important factor to tune the thickness of graphene layers of the Ni_x Cu_y @ NG-NC composites and the associated electrocatalytic performance. Due to the collective effects including unique porous flowered architecture and the synergetic effect between the bimetallic alloy core and graphene shell, the Ni₃ Cu₁ @ NG-NC electrocatalyst obtained under optimized conditions exhibits highly efficient and ultrastable activity toward HER in harsh environments, i.e., a low overpotential of 122 mV to achieve a current density of 10 mA cm^-2 with a low Tafel slope of 84.2 mV dec^-1 in alkaline media, and a low overpotential of 95 mV to achieve a current density of 10 mA cm^-2 with a low Tafel slope of 77.1 mV dec^-1 in acidic electrolyte.

Electric Field-Driven Interfacial Alloying for in Situ Fabrication of Nano-Mo2C on Carbon Fabric as Cathode toward Efficient Hydrogen Generation

A binderless composite cathode for efficient electrocatalytic hydrogen evolution reaction (HER), Mo₂C-decorated carbon cloth (denoted as CC/MC), is simply fabricated via a novel and unique strategy which involves a solid-solid phase interfacial electrochemical reaction between carbon fiber and bulk-MoS₂ in molten NaCl-KCl (700 °C). MoS₂, evenly coated on carbon cloth (CC), is electrochemically reduced in situ and readily reacts with the carbon fibers of CC current collector to form a Mo₂C nanoparticle layer. The experiment and calculation results show that the applied electric field results in a declining migration barrier of Mo vacancies in Mo₂C lattice, which promotes the diffusion of Mo atoms into carbon across the interfacial Mo₂C layer, thereby impelling the combination of Mo with C in depth. The electrochemical tests indicate that the optimized cathode (CC/MC-2) exhibits a small overpotential of 134.4 mV at 10 mA cm^-2 and stays stable for HER in acidic media. The catalytic capacity for N₂ reduction of CC/MC-2 is analyzed. In addition, a Ni-doped Mo₂C-modified carbon fabric electrode with enhanced HER activity (η₁₀ = 96.6 mV) can be prepared through a similar process.

Ni/Ni3C core–shell nanoparticles encapsulated in N-doped bamboo-like carbon nanotubes towards efficient overall water splitting

A novel electrocatalyst of Ni/Ni₃C core–shell nanoparticles embedded in bamboo-like N-doped carbon nanotubes has been successfully synthesized, which exhibits superior overall water splitting performance in alkaline solution.

Fe5C2 nanoparticles as low-cost HER electrocatalyst: the importance of Co substitution

Constructing and understanding the doping effect of secondary metal in transition metal carbide (TMC) catalysts is pivotal for the design of low-cost hydrogen evolution reaction (HER) electrocatalysts. In this work, we developed a wet-chemistry strategy for synthesizing Co-modified Fe₅C₂ nanoparticles ((Fe_1-xCo_x)₅C₂ NPs) as highly active HER electrocatalysts in basic solution. The structure of (Fe_1-xCo_x)₅C₂ NPs was characterized by X-ray diffraction (XRD), extended X-ray absorption fine structure spectra (EXAFS) and scanning/transmission electron microscopy (S/TEM), indicating that the isomorphous substitution of cobalt in the lattice of Fe₅C₂. (Fe_0.75Co_0.25)₅C₂ exhibited the best HER activity (174 mV for j = -10 mA/cm²). Computational calculation results indicate that Co provides the most active site for HER. X-ray adsorption spectra (XAS) studies further suggested that the electron transfer in Fe-C bonds are enhanced by the substitution of Co, which modulates the hydrogen adsorption on the adjacent electronic-enriched carbon, and therefore promotes HER activity. Our results affirm the design of low-cost bimetallic TMCs based HER catalysts.

Flowerlike NiCo2S4 Hollow Sub-Microspheres with Mesoporous Nanoshells Support Pd Nanoparticles for Enhanced Hydrogen Evolution Reaction Electrocatalysis in Both Acidic and Alkaline Conditions

Flowerlike NiCo₂S₄ hollow sub-microspheres are synthesized through Cu₂O templates to support Pd nanoparticles as high-efficiency catalysts for the hydrogen evolution reaction (HER). The diameter and shell size of NiCo₂S₄ hollow sub-microspheres are about 400 and 16 nm, respectively. In addition, the surface of the shells is constructed by petallike nanosheets. About 3 nm Pd particles uniformly incorporate with the flowerlike NiCo₂S₄ hollow sub-microsphere to form the NiCo₂S₄/Pd heterostructure. The NiCo₂S₄/Pd catalysts exhibit significantly lower overpotential of only 87 and 83 mV at 10 mA/cm² for the HER in both acidic and alkaline conditions, respectively, relative to NiCo₂S₄ (247, 226 mV) and Pd (175, 385 mV) catalysts. Besides, the NiCo₂S₄/Pd catalysts also exhibit excellent stability of HER in these two conditions. The superior HER performance of NiCo₂S₄/Pd might be resulted from the unique architecture of metal nanoparticles anchored on the bimetallic sulfide flowerlike hollow sub-microspheres, which could provide high surface area, lots of active sites, strong synergetic effect, and stable structure.

Ni/Ni3C Core/Shell Hierarchical Nanospheres with Enhanced Electrocatalytic Activity for Water Oxidation

Developing efficient and low-cost catalysts with high activity and excellent electrochemical and structural stability toward the oxygen evolution reaction (OER) is of great significance for both energy and environment sustainability. Herein, Ni/Ni₃C core/shell hierarchical nanospheres have been in situ synthesized via an ionic liquid-assisted hydrothermal method at relatively low temperature. Ionic liquid 1-butyl-3-methylimidazolium acetate has played multiple roles in the whole synthesis process. Benefiting from the high electrical conductivity, more exposed active sites and the core/shell interface effect, the obtained Ni/Ni₃C core/shell hierarchical nanospheres exhibit an outstanding OER performance with lower overpotential, small Tafel slope, and excellent stability. This fundamental method and insights with in situ coupling high conductivity metal support and metal carbide in a core/shell nanoarchitecture by an ionic liquid-assisted hydrothermal method would open up a new pathway to achieve high-performance electrocatalysts toward the OER.

Atomic Layer Deposition of Nickel Carbide from a Nickel Amidinate Precursor and Hydrogen Plasma

A new atomic layer deposition (ALD) process for depositing nickel carbide (Ni₃C _x) thin films is reported, using bis( N, N'-di- tert-butylacetamidinato)nickel(II) and H₂ plasma. The process shows a good layer-by-layer film growth behavior with a saturated film growth rate of 0.039 nm/cycle for a fairly wide process temperature window from 75 to 250 °C. Comprehensive material characterizations are performed on the Ni₃C _x films deposited at 95 °C with various H₂ plasma pulse lengths from 5 to 12 s, and no appreciable difference is found with the change of the plasma pulse length. The deposited Ni₃C _x films are fairly pure, smooth, and conductive, and the x in the nominal formula of Ni₃C _x is approximately 0.7. The ALD Ni₃C _x films are polycrystalline with a rhombohedral Ni₃C crystal structure, and the films are free of nanocrystalline graphite or amorphous carbon. Last, we demonstrate that, by using this ALD process, highly uniform Ni₃C _x films can be conformally deposited into deep narrow trenches with an aspect ratio as high as 20:1, which thereby highlights the broad and promising applicability of this process for conformal Ni₃C _x film coatings on complex high-aspect-ratio 3D architectures in general.

A New Member of Electrocatalysts Based on Nickel Metaphosphate Nanocrystals for Efficient Water Oxidation

High-performance electrocatalysts are desired for electrochemical energy conversion, especially in the field of water splitting. Here, a new member of phosphate electrocatalysts, nickel metaphosphate (Ni₂ P₄ O₁₂ ) nanocrystals, is reported, exhibiting low overpotential of 270 mV to generate the current density of 10 mA cm^-2 and a superior catalytic durability of 100 h. It is worth noting that Ni₂ P₄ O₁₂ electrocatalyst has remarkable oxygen evolution performance operating in basic media. Further experimental and theoretical analyses demonstrate that N dopant boosts the catalytic performance of Ni₂ P₄ O₁₂ due to optimizing the surface electronic structure for better charge transfer and decreasing the adsorption energy for the oxygenic intermediates.

Hierarchically interconnected nitrogen-doped carbon nanosheets for an efficient hydrogen evolution reaction

Exploring low-cost and efficient electrocatalysts based on earth-abundant elements for the hydrogen evolution reaction (HER) is of great importance for the development of clean and renewable energy. In this work, we report a facile self-foaming strategy for synthesis of hierarchically interconnected nitrogen-doped carbon nanosheets (NCNS). The doping N species within the 3D interconnected carbon network affords rich active sites for the HER and facilitates fast charge transfer. As a result, the NCNS exhibit excellent catalytic activity with an onset potential of -65 mV, and a Tafel slope of 81 mV dec^-1 with robust stability over 10 h in acidic media. Further analyses suggest that the graphitic N species in the NCNS contribute to their catalytic activity. Such a high catalytic performance makes the NCNS a promising metal-free HER electrocatalyst for practical hydrogen production.

Strongly Coupled Molybdenum Carbide on Carbon Sheets as a Bifunctional Electrocatalyst for Overall Water Splitting

High-performance and affordable electrocatalysts from earth-abundant elements are desirably pursued for water splitting involving hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Here, a bifunctional electrocatalyst of highly crystalline Mo₂ C nanoparticles supported on carbon sheets (Mo₂ C/CS) was designed toward overall water splitting. Owing to the highly active catalytic nature of Mo₂ C nanoparticles, the high surface area of carbon sheets and efficient charge transfer in the strongly coupled composite, the designed catalysts show excellent bifunctional behavior with an onset potential of -60 mV for HER and an overpotential of 320 mV to achieve a current density of 10 mA cm^-2 for OER in 1 m KOH while maintaining robust stability. Moreover, the electrolysis cell using the catalyst only requires a low cell voltage of 1.73 V to achieve a current density of 10 mA cm^-2 and maintains the activity for more than 100 h when employing the Mo₂ C/CS catalyst as both anode and cathode electrodes. Such high performance makes Mo₂ C/CS a promising electrocatalyst for practical hydrogen production from water splitting.