Recent advances and future prospects on Ni_(3)S_(2)-Based electrocatalysts for efficient alkaline water electrolysis

Green hydrogen(H_(2))produced by renewable energy powered alkaline water electrolysis is a promising alternative to fossil fuels due to its high energy density with zero-carbon emissions.However,efficient and economic H_(2) production by alkaline water electrolysis is hindered by the sluggish hydrogen evolution reaction(HER)and oxygen evolution reaction(OER).Therefore,it is imperative to design and fabricate high-active and low-cost non-precious metal catalysts to improve the HER and OER performance,which affects the energy efficiency of alkaline water electrolysis.Ni_(3)S_(2) with the heazlewoodite structure is a potential electrocatalyst with near-metal conductivity due to the Ni–Ni metal network.Here,the review comprehensively presents the recent progress of Ni_(3)S_(2)-based electrocatalysts for alkaline water electrocatalysis.Herein,the HER and OER mechanisms,performance evaluation criteria,preparation methods,and strategies for performance improvement of Ni_(3)S_(2)-based electrocatalysts are discussed.The challenges and perspectives are also analyzed.

A novel multi-channel porous structure facilitating mass transport towards highly efficient alkaline water electrolysis

An advantageous porous architecture of electrodes is pivotal in significantly enhancing alkaline water electrolysis(AWE)efficiency by optimizing the mass transport mechanisms.This effect becomes even more pronounced when aiming to achieve elevated current densities.Herein,we employed a rapid and scalable laser texturing process to craft novel multi-channel porous electrodes.Particularly,the obtained electrodes exhibit the lowest Tafel slope of 79 mV dec^(-1)(HER)and 49 mV dec^(-1)(OER).As anticipated,the alkaline electrolyzer(AEL)cell incorporating multi-channel porous electrodes(NP-LT30)exhibited a remarkable improvement in cell efficiency,with voltage drops(from 2.28 to 1.97 V)exceeding 300 mV under 1 A cm^(-1),compared to conventional perforated Ni plate electrodes.This enhancement mainly stemmed from the employed multi-channel porous structure,facilitating mass transport and bubble dynamics through an innovative convection mode,surpassing the traditional convection mode.Furthermore,the NP-LT30-based AEL cell demonstrated exceptional durability for 300 h under 1.0 A cm^(-2).This study underscores the capability of the novel multi-channel porous electrodes to expedite mass transport in practical AWE applications.

Roles of heteroatoms in electrocatalysts for alkaline water splitting:A review focusing on the reaction mechanism

Alkaline water splitting is a promising technology for“green hydrogen”generation.To improve its efficiency,highly robust catalysts are required to reduce the overpotential for low electrical power consumption.Heteroatom modification is one of the most effective strategies for boosting catalytic performance,as it can regulate the physicochemical properties of host catalysts to improve their intrinsic activity.Herein,aiming to provide an overview of the impact of heteroatoms on catalytic activity at the atomic level,we present a review of the key role of heteroatoms in enhancing reaction kinetics based on the reaction pathways of the hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)in alkaline media.In particular,the introduction of heteroatoms can directly and indirectly optimize the interactions between the active sites and intermediates,thus improving the intrinsic activity.To clearly illustrate this influence in detail,we have summarized a series of representative heteroatom-modified electrocatalysts and discussed the important roles of heteroatoms in the OER and HER reaction pathways.Finally,some challenges and perspectives for heteroatom-modified electrodes are discussed.We hope that this review will be helpful for the development of efficient and low-cost electrocatalysts for water electrolysis and other energy conversion applications.

Design and operando/in situ characterization of precious-metal-free electrocatalysts for alkaline water splitting

Electrochemical water splitting has attracted considerable attention for the production of hydrogen fuel by using renewable energy resources.However,the sluggish reaction kinetics make it essential to explore precious-metal-free electrocatalysts with superior activity and long-term stability.Tremendous efforts have been made in exploring electrocatalysts to reduce the energy barriers and improve catalytic efficiency.This review summarizes different categories of precious-metal-free electrocatalysts developed in the past 5 years for alkaline water splitting.The design strategies for optimizing the electronic and geometric structures of electrocatalysts with enhanced catalytic performance are discussed,including composition modulation,defect engineering,and structural engineering.Particularly,the advancement of operando/in situ characterization techniques toward the understanding of structural evolution,reaction intermediates,and active sites during the water splitting process are summarized.Finally,current challenges and future perspectives toward achieving efficient catalyst systems for industrial applications are proposed.This review will provide insights and strategies to the design of precious-metalfree electrocatalysts and inspire future research in alkaline water splitting.

Epitaxially Grown Ru Clusters-Nickel Nitride Heterostructure Advances Water Electrolysis Kinetics in Alkaline and Seawater Media

The epitaxial heterostructure can be rationally designed based on the in situ growth of two compatible phases with lattice similarity,in which the modulated electronic states and tuned adsorption behaviors are conducive to the enhancement of electrocatalytic activity.Herein,theoretical simulations first disclose the charge transfer trend and reinforced inherent electron conduction around the epitaxial heterointerface between Ru clusters and Ni_(3)N substrate(cRu-Ni_(3)N),thus leading to the optimized adsorption behaviors and reduced activation energy barriers.Subsequently,the defectrich nanosheets with the epitaxially grown cRu-Ni_(3)N heterointerface are successfully constructed.Impressively,by virtue of the superiority of intrinsic activity and reaction kinetics,such unique epitaxial heterostructure exhibits remarkable bifunctional catalytic activity toward electrocatalytic OER(226 mV@20 mA cm^(−2))and HER(32 mV@10 mA cm^(−2))in alkaline media.Furthermore,it also shows great application prospect in alkaline freshwater and seawater splitting,as well as solar-to-hydrogen integrated system.This work could provide beneficial enlightenment for the establishment of advanced electrocatalysts with epitaxial heterointerfaces.

Optimizing electronic structure of NiFe LDH with Mn-doping and Fe_(0.64)Ni_(0.36)alloy for alkaline water oxidation under industrial current density

Alkaline electrolyzers for water splitting under the industrial current densities are always burdened with huge energy consumption due to the high overpotential and poor stability of the anode nanocatalysts for oxygen evolution reaction(OER).Inspired by the interfacial charge transfer for enhancing the performance,a series of in-situ grown interfacial Mn-NiFe lactate dehydrogenase(LDH)was designed on the Fe_(0.64)Ni_(0.36)/NM(nickel mesh)alloy layer.The optimized Mn_(0.15)-NiFe LDH/Fe_(0.64)Ni_(0.36)/NM exhibited an ultralow overpotential of 295 mV to drive 500 mA·cm^(-2)and an incredible stability under large current density.The interfacial space and heteroatom doping synergistically triggered the electronic structure optimization to promote electron transfer and ensure the durability of the high-current reaction.Notably,the designed Mn_(0.15)-NiFe LDH/Fe_(0.64)Ni_(0.36)/NM as an anode in an integral alkaline electrolyzer exhibited a cell voltage of 1.78 V at 500 mA·cm^(-2) with a stability of 366 h.Density functional theory(DFT)calculations further demonstrated the synergistic effect of alloy layer introduction and Mn doping could accelerate electron transfer and stabilize the charged active center to activate the NiFe LDH and reduce the OER energy barrier.Our work offers new insights into developing efficient self-supported catalysts for high-current alkaline water oxidation.

Prognostics and health management of alkaline water electrolyzer: Techno-economic analysis considering replacement moment

Recently,considerable attention has been paid to the installation of renewable energy capacity to mitigate global CO_(2) emissions.H_(2) produced using water electrolysis and renewable energy is regarded as a clean energy carrier,generating electricity without CO_(2) emissions,called‘Green H 2’.In this paper,a prognostics and health man-agement model for an alkaline water electrolyzer was proposed to predict the load voltage on the electrolyzer to obtain the state of health information.The prognostics and health management model was developed by training historical operating data via machine learning models,support vector machine and gaussian process regression,showing the root mean square error of 1.28×10^(−3) and 8.03×10^(−6).In addition,a techno-economic analysis was performed for a green H_(2) production system,composed of 1 MW of photovoltaic plant and 1 MW of alkaline water electrolyzer,to provide economic insights and feasibility of the system.A levelized cost of H_(2) of$6.89 kgH_(2)−1 was calculated and the potential to reach the levelized cost of H_(2) from steam methane reforming with carbon capture and storage was shown by considering the learning rate of the photovoltaic module and elec-trolyzer.Finally,the replacement of the alkaline water electrolyzer at around 10 years was preferred to increase the net present value from the green H_(2) production system when capital expenditure and replacement cost are low enough.

Boosting overall saline water splitting by constructing a strain-engineered high-entropy electrocatalyst

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

In situ Hydrothermal Oxidation of Ternary FeCoNi Alloy Electrode for Overall Water Splitting

Exploring noble metal-free catalyst materials for high efficient electrochemical water splitting to produce hydrogen is strongly desired for renewable energy development.In this article,a novel bifunctional catalytic electrode of insitu-grown type for alkaline water splitting based on FeCoNi alloy substrate has been successfully prepared via a facile one-step hydrothermal oxidation route in an alkaline hydrogen peroxide medium.It shows that the matrix alloy with the atom ratio 4∶3∶3 of Fe∶Co∶Ni can obtain the best catalytic performance when hydrothermally treated at 180℃for 18 h in the solution containing 1.8 M hydrogen peroxide and 3.6 M sodium hydroxide.The as-prepared Fe_(0.4)Co_(0.3)Ni_(0.3)-1.8 electrode exhibits small overpotentials of only 184 and 175 mV at electrolysis current density of 10 mA cm^(-2)for alkaline OER and HER processes,respectively.The overall water splitting at electrolysis current density of 10 mA cm^(-2)can be stably delivered at a low cell voltage of 1.62 V.These characteristics including the large specific surface area,the high surface nickel content,the abundant catalyst species,the balanced distribution between bivalent and trivalent metal ions,and the strong binding of in-situ naturally growed catalytic layer to matrix are responsible for the prominent catalytic performance of the Fe_(0.4)Co_(0.3)Ni_(0.3)-1.8 electrode,which can act as a possible replacement for expensive noble metal-based materials.

Handily etching nickel foams into catalyst-substrate fusion self‐stabilized electrodes toward industrial‐level water electrolysis

The key challenge of industrial water electrolysis is to design catalytic electrodes that can stabilize high current density with low power consumption(i.e.,overpotential),while industrial harsh conditions make the balance between electrode activity and stability more difficult.Here,we develop an efficient and durable electrode for water oxidation reaction(WOR),which yields a high current density of 1000 mA cm−2 at an overpotential of only 284 mV in 1M KOH at 25°C and shows robust stability even in 6M KOH strong alkali with an elevated temperature up to 80°C.This electrode is fabricated from a cheap nickel foam(NF)substrate through a simple one-step solution etching method,resulting in the growth of ultrafine phosphorus doped nickel-iron(oxy)hydroxide[P-(Ni,Fe)O_(x)H_(y)]nanoparticles embedded into abundant micropores on the surface,featured as a self-stabilized catalyst–substrate fusion electrode.Such self-stabilizing effect fastens highly active P-(Ni,Fe)O_(x)H_(y)species on conductive NF substrates with significant contribution to catalyst fixation and charge transfer,realizing a win–win tactics for WOR activity and durability at high current densities in harsh environments.This work affords a cost-effective WOR electrode that can well work at large current densities,suggestive of the rational design of catalyst electrodes toward industrial-scale water electrolysis.

Effect of Alkaline Electrolyzed Water on Performance Improvement of Green Concrete with High Volume of Mineral Admixtures

The strength and durability of concrete will be significantly reduced at high volume of mineral admixture,and the poor early strength of concrete also still needs to be solved.In this investigation,a highly active alkaline electrolyzed waters was used as mixing water to improve the early strength and enhance the durability of green concrete with high volume mineral admixture,the influences of alkaline electrolyzed water(AEW)on hydration activity of mineral admixture and durability of concrete were determined.The results showed that compared with natural tap water,AEW can accelerate early hydration process of cement in concrete and produce comparatively more hydrated products,leading to a 13.6%higher compressive strength than that of ordinary concrete at early age,but the improvement effect of AEW concrete was relatively reduced at long-term age.Meanwhile,the activity of mineral admixtures could be stimulated by AEW to some extent,the strength and durability performance of AEW concrete after double doping 25%slag and 25%fly ash can still reach the level of ordinary cement concrete without mineral admixtures.The SEM micromorphology of 7 d hydrated natural tap water cement paste was observed to be flaky and tabular,but the AEW cement pastes present obvious cluster and granulation phenomenon.The SEM microstructure of AEW concrete with mineral admixtures is more developed and denser than ordinary tap water concrete with mineral admixtures.Therefore,the AEW probably could realize the effective utilization of about 50%mineral admixture amount of concrete without strength loss,the cement production cost and associated CO_(2) emission reduced,which has a good economic and environmental benefit.

Enhancing the Efficiency of Multi-Electrolyzer Clusters with Lye Mixer:Topology Design and Control Strategy

The rise in hydrogen production powered by renewable energy is driving the field toward the adoption of systems comprising multiple alkaline water electrolyzers.These setups present various operational modes:independent operation and multi-electrolyzer parallelization,each with distinct advantages and challenges.This study introduces an innovative configuration that incorporates a mutual lye mixer among electrolyzers,establishing a weakly coupled system that combines the advantages of two modes.This approach enables efficient heat utilization for faster hot-startup and maintains heat conservation post-lye interconnection,while preserving the option for independent operation after decoupling.A specialized thermal exchange model is developed for this topology,according to the dynamics of the lye mixer.The study further details startup procedures and proposes optimized control strategies tailored to this structural design.Waste heat from the caustic fully heats up the multiple electrolyzers connected to the lye mixing system,enabling a rapid hot start to enhance the system’s ability to track renewable energy.A control strategy is established to reduce heat loss and increase startup speed,and the optimal valve openings of the diverter valve and the manifold valve are determined.Simulation results indicate a considerable enhancement in operational efficiency,marked by an 18.28%improvement in startup speed and a 6.11%reduction in startup energy consumption inmulti-electrolyzer cluster systems,particularlywhen the systems are synchronized with photovoltaic energy sources.The findings represent a significant stride toward efficient and sustainable hydrogen production,offering a promising path for large-scale integration of renewable energy.

Self-supporting NiFe LDH-MoS_(x) integrated electrode for highly efficient water splitting at the industrial electrolysis conditions

Developing effective and practical electrocatalyst under industrial electrolysis conditions is critical for renewable hydrogen production.Herein,we report the self-supporting NiFe LDH-MoS_(x) integrated electrode for water oxidation under normal alkaline test condition(1 M KOH at 25℃)and simulated industrial electrolysis conditions(5 M KOH at 65℃).Such optimized electrode exhibits excellent oxygen evolution reaction(OER)performance with overpotential of 195 and 290 mV at current density of 100 and 400 mA·cm^(-2) under normal alkaline test condition.Notably,only over-potential of 156 and 201 mV were required to achieve the current density of 100 and 400mA·cm^(-2) under simulated industrial electrolysis conditions.No significant degradations were observed after long-term durability tests for both conditions.When using in two-electrode system,the operational voltages of 1.44 and 1.72 V were required to achieve a current density of 10 and 100 mA·cm^(-2) for the overall water splitting test(NiFe LDH-MoS_(x)/INF||20%Pt/C).Additionally,the operational voltage of employing NiFe LDH-MoS_(x)/INF as both cathode and anode merely require 1.52 V at 50mA·cm^(-2) at simulated industrial electrolysis conditions.Notably,a membrane electrode assembly(MEA)for anion exchange membrane water electrolysis(AEMWEs)using NiFe LDH-MoS_(x)/INF as an anode catalyst exhibited an energy conversion efficiency of 71.8%at current density of 400 mA·cm^(-2)in 1 M KOH at 60℃.Further experimental results reveal that sulfurized substrate not only improved the conductivity of NiFe LDH,but also regulated its electronic configurations and atomic composition,leading to the excellent activity.The easy-obtained and cost-effective integrated electrodes are expected to meet the large-scale application of industrial water electrolysis.

Insight into the boosted activity of TiO2–CoP composites for hydrogen evolution reaction:Accelerated mass transfer,optimized interfacial water,and promoted intrinsic activity

The use of abundant elements in the earth as electrocatalytic hydrogen production catalysts is of great significance for hydrogen energy cycling.Herein,we report amorphous TiO_(2)-decorated CoP/NF(TiO_(2)–CoP/NF)as an excellent electrocatalyst for alkaline hydrogen evolution reaction(HER).The welldispersed amorphous TiO_(2)on nanoneedle-like CoP arrays preserves the crystal structure of CoP and changes its electronic structure by interfacial charge transfer.Compared to CoP/NF catalyst,the Ti O_(2)–CoP/NF composite catalyst exhibits high HER activity with an overpotential of 61 mV at 10 mA cm^(-2)and high stability.Importantly,it almost maintains the Volmer step as a rate-determining step(RDS)and the Tafel slope at a wide cathodic potential range showing the fast kinetics under large polarization regions.Theoretical simulations reveal that the combination of TiO_(2)and CoP selectively accelerates the hydrated K+diffusion,regulates the interfacial water orientation to adapt to the subsequent smooth water dissociation,and optimizes*H adsorption/H_(2)desorption.The strengthened coupling of HER multi-scale-processes on transition metal compound composites catalysts is the underlying mechanism for improving HER activity.

Tailoring synergetic catalytic interface of VPO/Ni_(2)P to boost hydrogen evolution under alkaline conditions

Design of the catalyst for efficient water dissociation and hydrogen recombination is paramount in enhancement of the alkaline water electrolysis kinetics.Herein,we reported a delicate hierarchical(VO)_(2) P_(2)O_(7)-Ni_(2) P@NF(VPO-Ni_(2) P@NF)hybrid catalyst that operated efficiently in alkaline media.The VPO and Ni_(2) P respectively act as the water dissociation promoter and the hydrogen recombination center,which synergistically propel water adsorption/dissociation and H intermediates recombination.The resulting synergistic interfaces between VPO and Ni_(2) P are verified to afford the catalyst an outstanding performance for hydrogen evolution reaction in alkaline media with an overpotential of 154 mV at 10 mA cm^(-2),Tafel slope of 65 mV dec^(-1),and remarkable durability.Furthermore,the catalyst presents the potential for overall water splitting.This work may shed fresh light on the high-performance electrocatalyst design and the application of VPO on water electrolysis.

Hetero-interfacial nickel nitride/vanadium oxynitride porous nanosheets as trifunctional electrodes for HER,OER and sodium ion batteries

The development of single electrode with multifunctional purposes for electrochemical devices remains a symbolic challenge in recent technology.This work explores interfacially-rich transition metal nitride hybrid that consist of nickel nitride and vanadium oxynitride(VO_(0.26)N_(0.52))on robust carbon fiber(denoted CF/Ni_(3)N/VON)as trifunctional electrode for hydrogen evolution reaction(HER),oxygen evolution reaction(OER),and sodium ion batteries(SIBs).The as-prepared CF/Ni_(3)N/VON exhibits low HER overpotential of 48 m V@10 m A cm^(-2),OER overpotential of 287 m V@10 m A cm^(-2),and sodium-ion anode storage reversible capacity of 555 m A h g^(-1)@0.2 C.Theoretical analyses reveal that the Ni_(3)N effectively facilitates hydrogen desorption for HER,increases the electrical conductivity for OER,and promotes the Na-ion storage intercalation process,while the VON substantially elevates the water dissociation kinetics for HER,accelerates the adsorption of OH*intermediate for OER and enhances the Na-ion surface adsorption storage process.Owing to the excellent HER and OER performances of the CF/Ni_(3)N/VON electrode,an overall water splitting device denoted as CF/Ni_(3)N/VON//CF/Ni_(3)N/VON was not only assembled showing an operating voltage of 1.63 V at current density of 10 m A cm^(-2)but was also successfully self-powered by the assembled CF/Ni_(3)N/VON//CF/Na_(3)V_(2)(PO_(4))_(3) flexible sodium ion battery.This work will contribute to the development of efficient and cost-effective flexible integrated electrochemical energy devices.

Surface distribution of alkalinity and specific alkalinity and their application to water mass tracing in Kuroshio area of the East China Sea

Surface distribution and seasonal variation of alkalinity and specific alkalinity in Kuroshio area of the East ChinaSea and their application to the water mass tracing are discussed in this paper. Results show a distinct seasonal variation of the alkalinity, which is concerned with the process of vertical mixing. Different specific alkalinity in various water masses has been found. On the basis of the difference of the specific alkalinity and the distribution of alkalinity, two water fronts in summer season, located at 27°-30°N and 124°-1 27°E, (Ⅰ), and at the northern waters about one latitude from the Taiwan Island, (Ⅱ); one in winter season at about one longitude from coast of mainland of China and 26°-30°N were found. In summer season, about 1-2 longitudes eastward shift of front (Ⅰ) is found by comparison of data in May and August. And the high alkalinity of the northern East China Sea in summer season may be caused by the Huanghe River runoff flowing southward along with the Huanghai Sea Coastal Current.

Geological Genesis of Alkaline Magnesium-Type Groundwater within the Ophiolitic Rocks Areas in Southwestern Turkey

The groundwaters within the ophiolite nappes in the southwestern part of Turkey have different physical and geochemical characteristics and are divided into five different groundwater facies.These are(1) Mg-HCO_(3),(2) Mg-HCO_(3)-CO_(3),(3) Mg-CO_(3)-HCO_(3),(4) Na-Ca-Cl-CO_(3),and(5) Ca-MgHCO_(3).The waters interact with ophiolites,mainly made up of basic-ultrabasic rocks,are characterized by alkaline and hyperalkaline character.Alkaline waters have high Mg,HCO_(3)contents and Mg/Ca ratio,and hyperalkaline water has high Na,Ca contents,and low Mg/Ca ratio.The waters in the study area formed by the interaction of meteoric waters with variously serpentinized ultramafic rocks under low-temperature conditions.Silicate weathering is the main hydrogeochemical process that plays a role in the chemical composition of water.Mg-HCO_(3)-type groundwaters are produced under open-system conditions with respect to CO_(2)due to meteoric water-serpentinized peridotite interactions in a shallow environment.Deep-seated groundwaters are Na-Ca-Cl-CO_(3)-type waters with high pH(TN-8 sample with p H 10.72),depleted in terms of Mg due to water-peridotite interaction under closed-system conditions with respect to CO_(2).Salda Lake with an alkaline character and high Mg and Na content is characterized by high evaporation and hydromagnesite deposition.

Noble-Metal-Free Oxygen Evolution Reaction Electrocatalysts Working at High Current Densities over 1000 mA cm^(-2):From Fundamental Understanding to Design Principles

Alkaline water electrolysis provides a promising route for"green hydrogen"generation,where anodic oxygen evolution reaction(OER)plays a crucial role in coupling with cathodic hydrogen evolution reaction.To date,the development of highly active and durable OER catalysts based on earth-abundant elements has drawn wide attention;nevertheless,their performance under high current densities(HCDs≥1000 mA cm^(-2))has been less emphasized.This situation has seriously impeded large-scale electrolysis industrialization.In this review,in order to provide a guideline for designing high-performance OER electrocatalysts,the effects of HCD on catalytic performance involving electron transfer,mass transfer,and physical/chemical stability are summarized.Furthermore,the design principles were pointed out for obtaining efficient and robust OER electrocatalysts in light of recent progress of OER electrocatalysts working above 1000 mA cm^(-2).These include the aspects of developing self-supported catalytic electrodes,enhancing intrinsic activity,enhancing the catalyst-support interaction,engineering surface wettability,and introducing protective layer.Finally,summaries and outlooks in achieving OER at industrially relevant HCDs are proposed.

Self-supported NiFe-LDH nanosheets on NiMo-based nanorods as high-performance bifunctional electrocatalysts for overall water splitting at industrial-level current densities

Efficient,durable and economic electrocatalysts are crucial for commercializing water electrolysis technology.Herein,we report an advanced bifunctional electrocatalyst for alkaline water splitting by growing NiFe-layered double hydroxide(NiFe-LDH)nanosheet arrays on the conductive NiMo-based nanorods deposited on Ni foam to form a three-dimensional(3D)architecture,which exhibits exceptional performances for both hydrogen evolution reaction(HER)and oxygen evolution reaction(OER).In overall water splitting,only the low operation voltages of 1.45/1.61 V are required to reach the current density of 10/500 mA·cm^(-2),and the continuous water splitting at an industrial-level current density of 500 mA·cm^(-2) shows a negligible degradation(1.8%)of the cell voltage over 1000 h.The outstanding performance is ascribed to the synergism of the HER-active NiMo-based nanorods and the OER-active NiFe-LDH nanosheet arrays of the hybridized 3D architecture.Specifically,the dense NiFe-LDH nanosheet arrays enhance the local pH on cathode by retarding OH-diffusion and enlarge the electrochemically active surface area on anode,while the conductive NiMo-based nanorods on Ni foam much decrease the charge-transfer resistances of both electrodes.This study provides an efficient strategy to explore advanced bifunctional electrocatalysts for overall water splitting by rationally hybridizing HER-and OER-active components.