Electrocatalysts For Alkaline Water Electrolysis Research Articles

Maximizing Bifunctionality for Overall Water Splitting by Integrating H2 Spillover and Oxygen Vacancies in CoPBO/Co3O4 Composite Catalyst

In the pursuit of utilizing renewable energy sources for green hydrogen (H2) production, alkaline water electrolysis has emerged as a key technology. To improve the reaction rates of overall water electrolysis and simplify electrode manufacturing, development of bifunctional electrocatalysts is of great relevance. Herein, CoPBO/Co3O4 is reported as a binary composite catalyst comprising amorphous (CoPBO) and crystalline (Co3O4) phases as a high‐performing bifunctional electrocatalyst for alkaline water electrolysis. Owing to the peculiar properties of CoPBO and Co3O4, such as complementing Gibbs free energy values for H‐adsorption (ΔGH) and relatively smaller difference in their work functions (ΔΦ), the composite exhibits H2 spillover (HS) mechanism to facilitate the hydrogen evolution reaction (HER). The outcome is manifested in the form of a low HER overpotential of 65 mV (at 10 mA cm−2). Moreover, an abundant amount of surface oxygen vacancies (Ov) are observed in the same CoPBO/Co3O4 composite that facilitates oxygen evolution reaction (OER) as well, leading to a mere 270 mV OER overpotential (at 10 mA cm−2). The present work showcases the possibilities to strategically design non‐noble composite catalysts that combine the advantages of HS phenomenon as well as Ov to achieve new record performances in alkaline water electrolysis.

FeCoNi-based Alloy Coatings as Low Overpotential Electrocatalysts for Alkaline Water Electrolysis.

Developing efficient, stable and low-cost electrocatalysts is a viable approach to solve the current energy crisis. It is found that increasing the surface area of the electrodes can effectively promote the electrocatalytic efficiency. Herein, the atmospheric plasma spraying (APS) technology was used to prepare FeCoNi-Ni3C alloy coating by adding Ni3C powder to FeCoNi powder with an equal molar ratio. The atomic ratios of Ni3C in the powder are 25 %, 50 %, and 75 %, respectively. The results prove that the pores on the surface of the coating have increased after Ni3C doping, which can provide more active sites in the electrocatalytic process to promote the electrocatalytic reaction. By controlling the proportion of Ni3C, the porosity of the coating surface can be effectively regulated. In 1.0 M KOH electrolyte and 10 mA cm-2, the50 at.% Ni3C coatingshows an overpotential of 105 mV and 212 mV for HER and OER, respectively. It is worth noting that the 50 at.% Ni3C coating has a low Tafel slope of 45.78 mV dec-1(HER) and 44 mV dec-1(OER). Furthermore, the 50 %at. Ni3C coating catalyst has a low potential of 1.664 V at 10 mA cm-2in a water-splitting system.

Electrodeposited NiB Films as Bifunctional Electrocatalysts in Alkaline Water Electrolizer

Abstract Sustainable electrochemical energy generation requires cost-effective, noble-metal-free electrocatalysts for hydrogen and oxygen production in electrolyzers. This study used electrodeposition to create crystalline NiB films with different boron (B) contents—Ni-B(1.17 wt.%), Ni-B(1.06 wt.%), Ni-B(0.94 wt.%), and Ni-B(0.89 wt.%)—on FTO substrates. These films were tested as bifunctional electrocatalyst electrodes for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) in alkaline media. The NiB films' composition and morphology were analyzed using SEM, AFM, XRD, GD-OES, and XPS. Linear sweep voltammetry assessed their electrocatalytic performance. Higher B content in the films promoted the formation of electroactive NiOOH, enhancing the OER. The Ni-B(1.17 wt.%) electrode required an overpotential of 380 mV to reach 10 mA cm⁻² for OER, while the Ni-B(1.06 wt.%) electrode required 146 mV for the same current density for HER. An alkaline water electrolyzer using Ni-B(1.17 wt.%) as the anode and Ni-B(1.06 wt.%) as the cathode achieved a current density of 10 mA cm⁻² at 1.71 V for overall water splitting. The system showed stability over 12 hours of testing. The results indicate that NiB films on FTO substrates are promising, low-cost bifunctional electrocatalysts for alkaline water electrolysis, offering an alternative to noble-metal-based electrocatalysts.

Tailoring the Heterointerfaces of Earth-Abundant Transition-Metal Nanoclusters on Nickel Oxide Nanosheets for Enhanced Overall Water Splitting through Electronic Structure Optimization.

Evolving highly competent and economical electrocatalysts for alkaline water electrolysis is crucial in renewable hydrogen energy technologies. The slow hydrogen evolution reaction (HER)/oxygen evolution reaction (OER) kinetics under alkaline electrolytes, still, has troubled developments in high-performance green hydrogen production systems. Herein, we demonstrate the tailoring of the interface of earth-abundant transition-metal nanoclusters (MNCs), including iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu) nanoclusters on nickel oxide nanosheets (M NCs|NiO NS) through metal-support interaction for enriched overall water splitting under an alkaline electrolyte. The strong metal-metal oxide interaction allows alteration of the binding capabilities of hydrogen ions (*H) and hydroxyl ions (*OH) on Ni electrodes. Specifically, the robust interaction between Fe and NiO reveals optimized binding of H* and OH* energies, facilitating the water-splitting reaction under an alkaline electrolyte. In addition, the improved HER/OER catalytic activity is attained with the Fe NCs|NiO NS with small overpotentials of ∼62.0 and ∼380.0 mV for the HER and OER, respectively, a high mass activity of ∼90.0 A g-1, a turnover frequency of ∼5.94 s-1, and long-lasting stability via offering abundant electrochemical active sites, three-dimensional (3D) morphologies, and high dispersion of nanoclusters that provide effective charge and mass transport processes. This study provides a promising strategy for the effective design of efficient bifunctional electrocatalysts based on earth-abundant materials for alkaline water electrolyzers.

Biology-Based Synthesis of Nickel Single Atoms on the Surface of Geobacter sulfurreducens as an Efficient Electrocatalyst for Alkaline Water Electrolysis.

Single-atom metal catalysts are promising electrocatalysts for water electrolysis. Nickel-based electrocatalysts have shown attractive application prospects for water electrolysis. However, synthesizing stable Ni single atoms using chemical and physical approaches remains a practical challenge. Here, a facile and precise method for synthesizing stable nickel single atoms on the surface of Geobacter sulfurreducens using a microbial-mediated extracellular electron transfer (EET) process is demonstrated. It is shown that G. sulfurreducens can effectively anchor nickel single atoms on their surface. X-ray absorption near-edge structure and Fourier-transformed extended X-ray absorption fine structure spectroscopy confirm that the nickel single atom is coordinated to nitrogen in the cytochromes. The as-synthesized nickel single atoms on G. sulfurreducens exhibit excellent bifunctional catalytic properties for alkaline water electrolysis with low overpotential (η) to achieve current density (10mAcm-2) for both hydrogen evolution reactions (η = 80mV) and oxygen evolution reaction (η = 330mV) with minimal catalyst loading of 0.0015mgNicm-2. The nickel single-atom catalyst shows long-term stability at a constant electrode potential. This synthesis method based on the EET capability of electroactive bacteria provides a simple and scalable approach for producing low-cost and highly efficient nonnoble transition metal single-atom catalysts for practical applications.

H2S-Treated Nickel Foam Electrocatalyst for Alkaline Water Electrolysis under Industrial Conditions

H₂S-Treated Nickel Foam Electrocatalyst for Alkaline Water Electrolysis under Industrial Conditions

Hierarchical nanoflowers of Bi/Fe-based selenide as a bifunctional electrocatalyst for alkaline water electrolysis

The current study presents a freestanding bifunctional electrocatalyst comprising hierarchically assembled Bi/Fe-based selenide with a nanoflower-like morphology on Ni foam for water electrolysis application. The impact of systematically adding Fe ions to Bi2Se3 on the phase and morphology is elaborately discussed. It is shown that tuning the Bi/Fe molar ratio governs the phase, electronic bandgap, and morphology, driven by the evolution of hetero-interfacial chemistry. The existence of multivalent metal ions, lattice defects, and an extended surface area remarkably improves the electrocatalytic activity. The optimized nanoflower-like composite electrode (1Bi1Fe-Se@NF) exhibits robust electrocatalytic efficacy with extremely low overpotentials of ∼53 mV and ∼230 mV at 10 mA cm−2 for hydrogen and oxygen evolution reactions, respectively. The symmetrical alkaline electrolyser, utilizing 1Bi1Fe-Se@NF electrodes (+,−), operates at a cell voltage of ∼1.52 V at 10 mA cm−2, lower than the device equipped with commercial Pt/C@NF (-) and RuO2@NF (+) (∼1.57 V). Even after 100 h of operation at 50 mA cm−2, the symmetrical cell maintains a stable voltage, highlighting the outstanding bifunctional catalytic activities of noble metal-free 1Bi1Fe-Se@NF for overall water electrolysis.

Facile and fast route of electrodepositing chloride ion-modified NiFePt layered double hydroxides for hydrogen evolution reaction

NiFe-based layered double hydroxide (LDH) is a promising electrocatalyst for alkaline water electrolysis because of the low cost and earth abundance of Ni and Fe, as well as their characteristic layered structure resulting in high electrocatalytic performance. However, its hydrogen evolution reaction (HER) activity is still insufficient compared to existing catalysts. Additionally, the hydrothermal method, a common LDH fabrication method, can be time-consuming and complicated. Herein, we suggest a facile route for the preparation of HER catalyst within tens of seconds using one-pot electrodeposition with only a few ionic additives. A trace amount of Pt ion was added to enhance the HER performance and chloride (Cl−) ion was used to increase the specific surface area of the catalyst as well as to control the reduction of Pt ion for Pt-O bonding. Consequently, the 2.5 mmol Cl− ion treated NiFePt LDH (NiFePt_Cl LDH) requires an overpotential of only 52 mV to reach a current density of 100 mA cm−2 and significantly improved durability, with an overpotential increase of only 7 mV at 100 mA cm−2 after 1,000 cyclic voltammetry scans.

Alkaline Water Electrolysis for Green Hydrogen Production.

ConspectusThe global energy landscape is undergoing significant change. Hydrogen is seen as the energy carrier of the future and will be a key element in the development of more sustainable industry and society. However, hydrogen is currently produced mainly from fossil fuels, and this needs to change. Alkaline water electrolysis with advanced technology has the most significant potential for this transition to produce large-scale green hydrogen by utilizing renewable energy. The assembly of industrial electrolyzer plants is more complex on a larger scale, but it follows a basic working principle, which involves two half-cells of anode and cathode sites where the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) occur. Out of the two reactions, the OER is more challenging both thermodynamically and kinetically. Besides having access to renewable electricity, developing durable and abundant electrocatalysts for the OER remains a challenge in large-scale alkaline water electrolysis. Among different physicochemical properties, the electrocatalyst surface and its interaction with water and reaction intermediates, as well as formed molecular hydrogen and oxygen, play an essential role in the catalytic performance and the reaction mechanism. In particular, the binding strengths between the catalyst surface and intermediates determine the rate-limiting step and electrocatalytic performance.This Account gives some insights into the status of the hydrogen economy and basic principles of alkaline water electrolysis by covering its fundamentals as well as industrial developments. Further, the HER and OER reaction mechanisms of alkaline water electrolysis and selected electrocatalyst progress for both half-reactions are briefly discussed. The Adsorbate Evolution Mechanism and the Lattice Oxygen Mechanism for the OER are explained with specific references. This Account also deliberates on the author's selected contributions to the development of transition metal-based electrocatalysts for alkaline water electrolysis with an emphasis on OER. The focus is particularly given to the enhancement of intrinsic activity, the role of eg-filling, phase segregation, and defect structure of cobalt-based electrocatalysts for OER. Structural modification and phase transformation of the cobalt oxide electrocatalyst under working conditions are further deliberated. In addition, the creation of new active surface species and the activation of cobalt- and nickel-based electrocatalysts through iron uptake from the alkaline electrolyte are discussed. In the end, this Account provides a brief overview of challenges related to large-scale production and utilization of green hydrogen.

Nanocrystalline (NixCo(1-x))3(PO4)2@FeSe2/NF as a promising OER electrocatalyst for alkaline water electrolysis

Affordable and sustainable hydrogen production is the need of the hour owing to the mounting global pursuit for the hydrogen economy. Water splitting is the premier go-to method to produce green hydrogen at a larger scale in which the half-cell Oxygen Evolution Reaction (OER) demands a larger amount of energy expenditure due to its sluggish kinetics. Hence, designing an efficient OER electrocatalyst, especially for alkaline water electrolysis that offers alternatives to the usage of precious group metals is a pressing priority. Herein, we report a novel nanocrystalline electrocatalyst consisting of two components, namely cobalt nickel phosphate and iron diselenide synthesised via a two-step electrodeposition at room temperature. The combination of the two components on the porous nickel foam substrate exhibits an overpotential of 272 mV at 100 mA/cm2 in 1 M KOH showing a low Tafel slope of a mere 38 mV/dec with appreciable retention even after 24 h of stability test at a relatively higher current density. The surface reconstruction that occurs when FeSe2 is electrodeposited on (Ni0.35Co0.65)3(PO4)2@NF and the synergy between the two components is the primary reason for the improved performance. Thus, this work highlights the ambient synthesis of a highly durable earth-abundant metal-based electrocatalyst which exceeds the performance of the standard Ru/C by a decent margin.

Multi-interface engineering of nickel-based electrocatalysts for alkaline hydrogen evolution reaction

High gravimetric energy density and zero carbon emission of hydrogen have motivated hydrogen energy to be an attractive alternative to fossil fuels. Electrochemical water splitting in alkaline medium, driven by green electricity from renewable sources, has been mentioned as a potential solution for sustainable hydrogen production. Hydrogen evolution reaction (HER), as a cathodic half-reaction of water splitting, requires additional overpotential to obtain protons via water adsorption/dissociation, suffering from slow kinetics in alkaline solution. Robust and active nickel (Ni)-based electrocatalyst is a promising candidate for achieving precious-metal comparable performance owing to its platinum-like electronic structures with more efficient electrical power consumption. Various modification strategies have been explored on Ni-based catalysts, among which multi-interface engineering is one of the most effective routines to optimize both the intrinsic activity of Ni-based electrocatalysts and the extrinsic stacked component limitations. Herein, we systematically summarize the recent progress of multi-interface engineering of Ni-based electrocatalysts to improve their alkaline HER catalytic activity. The origin of sluggish alkaline HER kinetics is first discussed. Subsequently, three kinds of interfaces, geometrically and reactively, conductive substrate/electrocatalyst interface, electrocatalyst internal heterointerface, and electrocatalyst/electrolyte interface, were cataloged and discussed on their contribution mechanisms toward alkaline HER. Particular focuses lie on the microstructural and electronic modulation of key intermediates with energetically favorable adsorption/desorption behaviors via rationally designed interfaces. Finally, challenges and perspectives for multi-interface engineering are discussed. We hope that this review will be inspiring and beneficial for the exploration of efficient Ni-based electrocatalysts for alkaline water electrolysis.

Benchmarking Activity and Stability of Layered Double Hydroxides (LDHs) Electrocatalysts for Alkaline Water Electrolysis

In order to reduce the cost of producing hydrogen through water electrolysis, novel technologies must be improved. Recently, the merging of conventional alkaline electrolysis (AEL) and proton exchange membrane electrolysis (PEM) has led to the development of anion exchange membrane electrolysis (AEMWE), which offers several advantages over AEL and PEM. In a nutshell, this technique employs cheap, abundant, and easily available (non-geostrategic) transition metals with anionic exchange membranes, overcoming the drawbacks of AEL and PEM.[1]To reach the readiness level of this technology, new and scalable synthetic routes for catalysts that lower the overpotential of the sluggish oxygen evolution reaction (OER) are required. Amongst all the OER catalysts reported in the literature, Layered Double Hydroxides (LDHs) have gained increasing attention due to their low overpotentials and stabilities.[2] Besides, electrochemical protocols to determine the activity and stability of these catalysts in different electrochemical cells must be established to understand their properties. Thus, this work focuses on the advantages and limitations of different electrochemical techniques, such as rotating disk electrode (RDE), three-electrode cells, and single-cell tests, to determine the activity and stability of two different LDHs. Unlike laboratory scale LDHs ‒prepared by hydrothermal treatment (HT-LDH)‒ room temperature synthesized LDHs (RT-LDH) can be prepared in kilogram quantities and present chemical structure and morphology differences. In this work, the LDHs have been characterized with spectroscopic techniques to correlate the chemical structure and morphology of the materials to their electrochemical response by RDE, three-electrode cells, and single-cell measurements.All in all, the scalable RT-LDH presents higher activity compared to HT-LDH in all three techniques. On the one hand, small current densities can only be reached by RDE, and the short-term stability of the materials is affected by the catalyst layer interface. On the other side, single-cell test measurements require long operational times, and the contribution of the membrane degradation to the overall cell voltage is still unclear. Thus, three-electrode cell measurements offer the possibility of characterizing LDHs at relevant current densities in a fast and straightforward manner, without membrane contributions, and are further employed in this work to study the stability of these systems.

A novel polyaniline based nanocomposite derived from used tea biomass: a promising electrocatalyst for oxygen evolution reaction

A potential electrocatalyst for alkaline water electrolysis was prepared by using an inexpensive used tea dust biomass wherein the used tea dust biomass was subjected for calcination followed by polymerization with varied amounts of monomer, aniline, to prepare nanocomposites. The thoroughly characterized nanocomposites were tested as potential electrocatalysts for oxygen evolution reaction (OER). The nanocomposite prepared using 5 mL of aniline requires an overpotential of only 380 mV (1.61 V vs RHE) to generate the current density of 250 mA cm−2 while the sample prepared without aniline requires 450 mV (1.68 V vs RHE) to generate the same amount of current density. Adding optimum amounts of polyaniline increases the number of active sites and conductivity, which are beneficial to facilitate OER. This study demonstrates successful conversion of tea waste biomass, produced in every home, into potential electrocatalyst, which can be used to generate environmentally benign carbon free hydrogen fuel.

One-Step Electrodeposition of NiMoP/NF as an Efficient and Cost-Effective Cathodic Electrocatalyst for Alkaline Water Electrolysis

One-Step Electrodeposition of NiMoP/NF as an Efficient and Cost-Effective Cathodic Electrocatalyst for Alkaline Water Electrolysis

Bimetallic Cu–Ni core–shell nanoparticles anchored N-doped reduced graphene oxide as a high-performance bifunctional electrocatalyst for alkaline water splitting

Water electrolysis is regarded as the most promising method for developing sustainable energy technologies. However, low-cost bifunctional electrocatalysts with high efficacy and long-term stability are required to make this method economically viable. Core-shell nanoparticles, which comprise a thin layer of a catalytically active shell surrounding a subsurface core, have recently emerged as cutting-edge electrocatalysts for effective water electrolysis. Herein, we systematically fabricated distinct bimetallic Cu–Ni particles by tuning the Cu:Ni ratios, and then anchored them to an N-doped reduced graphene oxide (NRG) backbone for alkaline water splitting. A Cu:Ni molar ratio of 1:1 was determined to be optimal for forming an effective core–shell configuration, affording favorable adsorption energies toward reactants. The Cu–Ni(1:1) core–shell nanoparticles anchored NRG, termed Cu–Ni(1:1)@NRG, displayed excellent performance toward the H2 evolution reaction (HER) and oxygen evolution reaction (OER), with overpotentials at 10 mA cm−2 of 107 and 310 mV, respectively, versus a reversible hydrogen electrode (RHE). This current density (10 mA cm−2) was attained at a low cell voltage of 1.64 V when Cu–Ni(1:1)@NRG was used as the bifunctional electrocatalyst for alkaline water electrolysis. Furthermore, the Cu–Ni(1:1)@NRG electrocatalyst exhibited outstanding long-term stability in prolonged electrocatalytic studies at a constant current density.

Investigation of Charge–Discharging Behavior of Metal Oxide–Based Anode Electrocatalysts for Alkaline Water Electrolysis to Suppress Degradation due to Reverse Current

In the bipolar-type alkaline water electrolysis powered by renewable energy, electrocatalysts are degraded by repeated potential change associated with the generation of reverse current. If an electrode has large discharge capacity, the opposite electrode on the same bipolar plate is degraded by the reverse current. In this study, discharge capacity of various transition metal-based electrocatalysts was investigated to clarify the determining factors of electrocatalysts on the reverse current and durability. The discharge capacities from 1.5 to 0.5 V vs. RHE (Qdc,0.5) of electrocatalysts are proportional to the surface area in most cases. The proportionality coefficient, corresponding to the specific capacity, is 1.0 C·m–2 for Co3O4 and 2.3 C·m–2 for manganese-based electrocatalysts. The substitution of Co3+ in Co3O4 with Ni3+ increased Qdc,0.5. The upper limit of theoretical specific capacity for Co3O4 is estimated to be 1.699 C·m–2, meaning the former and latter cases correspond to 2- and 1-electron reactions, respectively, per a cation at the surface. The discharge capacities of the elctrocatalysts increased because of the dissolution and recrystallization of nickel and/or cobalt into metal hydroxides. The increase in the capacities of Co3O4 and NiCo2O4 during ten charge–discharge cycles was below 2–9% and 0.5–38%, respectively. Therefore, if a cathode electrocatalyst with relatively low redox durability is used on the one side of a bipolar plate, it is necessary to control optimum discharge capacity of the anode by changing surface area and constituent metal cations to minimize the generation of reverse current.Graphical

Thin Films Fabricated by Pulsed Laser Deposition for Electrocatalysis

Thin Films Fabricated by Pulsed Laser Deposition for Electrocatalysis

Quad-metallic MOF-derived carbon-armored pseudo-high entropy alloys as a bifunctional electrocatalyst for alkaline water electrolysis at high current densities

A quad-metallic pseudo-HEA catalyst, FeCoNiMo@C, was developed for water electrolysis, exhibiting outstanding bifunctional catalytic efficiency and stability, 500 mA cm−2@1.725 V and a 3.4% decay after a 50 h operation at 500 mA cm−2.

(Invited) Designing Microscale Structures for Enhanced Function of Electrocatalysts for Alkaline Water Electrolysis

Water electrolysis has already been implemented for many decades on an industrial scale. It does, however, remain an active area of research and development for the pursuit of materials that have enhanced electrocatalytic performance and prolonged durability. For example, the accumulation of gas bubbles on the surfaces of electrodes during water electrolysis remains a challenge. Persistent bubbles on the surfaces of electrocatalysts can block electrolyte access to the electrode and reduce the electrochemically active surface area. At current densities that are relevant to industrial applications an extensive portion of the electrode can become covered with bubbles. There are a range of solutions that are being utilized in industrial settings, but also additional solutions being sought to optimize the efficiency of these systems. These solutions include applied shear flows across the surfaces of the electrodes, the implementation of ultrasonic induced cavitation, and an increase in electrolyte temperature. These solutions require further expenditures of energy and decrease the overall energy efficiency of the system. Alternative approaches may yield a lower energy demand for maintaining accessibility of the electrolyte to the electrochemically active surface area. One approach is through the design of electrode surface architectures that can assist with the removal of gas bubbles during water electrolysis. This work includes a review of the progress made in preparing structured electrodes for the alkaline based water electrolysis and specifically for the oxygen evolution reaction. These structures can influence the dynamics that occur at the electrode-electrolyte interface, such as the growth, coalescence, and release of oxygen gas bubbles. Understanding the correlations between the structures on the electrodes and their influence on the function of these materials towards the gas evolution are sought to guide the future development of optimal surface structures that are self-cleaning. Designs of electrode surface architectures are sought that can improve the efficiency of electrodes toward this and other gas evolution reactions.

Facile construction of porous and heterostructured molybdenum nitride/carbide nanobelt arrays for large current hydrogen evolution reaction

The development of cost-effective, highly efficient and stable electrocatalysts for alkaline water electrolysis at a large current density has attracted considerable attention. Herein, we reported a one-dimensional (1D) porous Mo2C/Mo2N heterostructured electrocatalyst on carbon cloth as robust electrode for large current hydrogen evolution reaction (HER). The MoO3 nanobelt arrays and urea were used as the metal and non-metal sources to fabricate the electrocatalyst by one-step thermal reaction. Due to the in-situ formed abundant high active interfaces and porous structure, the Mo2C/Mo2N electrocatalyst shows enhanced HER activity and kinetics, as exemplified by low overpotentials of 54, 73, and 96 mV at a current density of 10 mA cm−2 and small Tafel slopes of 48, 59 and 60 mV dec−1 in alkaline, neutral and acid media, respectively. Furthermore, the optimal Mo2C/Mo2N catalyst only requires a low overpotential of 290 mV to reach a large current density of 500 mA cm−2 in alkaline media, which is superior to commercial Pt/C catalyst (368 mV) and better than those of recently reported Mo-based electrocatalysts. This work paves a facile strategy to construct highly efficient and low-cost electrocatalyst for water splitting, which could be extended to fabricate other heterostructured electrocatalyst for electrocatalysis and energy conversion.