A one-pot hydrothermal synthesis of morphologically controllable yolk-shell structured CoFe glycerate spheres for oxygen evolution reaction.

CoFe-based catalysts are efficient electrocatalysts for the oxygen evolution reaction (OER) in alkaline media. Here, we present a simple one-pot hydrothermal method for synthesizing a series of CoFe glycerates with controllable surface morphologies and investigate their potential as highly efficient catalysts for the OER in alkaline media. These CoFe glycerates exhibit a unique yolk-shell microsphere structure assembled from ultrathin nanosheets. The adjustment of the surface nanosheet size is achieved by varying the CoFe ratio, ensuring a more efficient electrocatalytic system for the OER process. Due to the abundant active sites provided by the yolk-shell structure and interleaved ultrathin nanosheets, Co3Fe1 glycerate (Co3Fe1 gly) demonstrates a low overpotential (283 mV) and a small Tafel slope (44.61 mV dec-1) at 10 mA cm-2. Additionally, Co3Fe1 gly exhibits excellent durability in alkaline electrolytes. Moreover, a series of characterizations demonstrate that the active sites of Co3Fe1 gly are the high-valence Co species generated during the OER process. This study opens a promising avenue for utilizing efficient and low-cost electrocatalysts to enhance OER performance.

Co-CoSe heterogeneous fibers with strong interfacial built-in electric field as bifunctional electrocatalyst for high-performance Zn-air battery.

The explorations of efficient electrocatalysts to accelerate oxygen reactions in a wide temperature range is a crucial issue to the development of zinc-air batteries (ZAB) for all-climate applications. Herein, the Co-CoSe heterogeneous furry fibers (Co-CoSe@NHF) are developed as a bifunctional oxygen electrocatalyst for ZAB towards wide-temperature range applications. The Co-CoSe heterostructure with large work function difference (ΔWF) endows interfacial electron redistribution, which builds strong interfacial built-in electric field (BIEF) and improves the oxygen reactions. Meanwhile, the Co-CoSe heterostructure is encapsulated by in-situ grown carbon nanotubes, and forms the hollow fiber (NHF) with furry surface and beads-on-string configuration. The highly porous and conductive NHF configuration facilitates the fast kinetics and favors to accommodates volume change during cycling. As a result, the Co-CoSe@NHF achieves the superior bifunctional properties and good reliability for oxygen reactions. Integrated with the Co-CoSe@NHF fiber, the ZAB cell delivers the superior power density (301 mW cm-2) and long-term cycling stability over 280 h at 25 °C, and maintains the power densities of 126 mW cm-2 even the temperature decreases to -25 °C. Moreover, the solid-state ZAB exhibits significant flexibility and superior properties in a wide temperature range. Therefore, this work not only proposes a new strategy to design the high-performance bifunctional electrocatalysts, but also propels the development of flexible power sources for all-climate applications.

Nanocrystalline transition metal tetraborides as efficient electrocatalysts for hydrogen evolution reaction at the large current density.

While great efforts have been made to improve the electrocatalytic activity of existing materials toward hydrogen evolution reaction (HER), it is also importance for searching new type of nonprecious HER catalysts to realize the practical hydrogen evolution. Herein, we firstly report nanocrystalline transition metal tetraborides (TMB4, TM=W and Mo) as an efficient HER electrocatalyst has been synthesized by a single-step solid-state reaction. The optimized nanocrystalline WB4 exhibits an overpotential as low as 172 mV at 10 mA/cm2 and small Tafel slope of 63 mV/dec in 0.5 M H2SO4. Moreover, the nanocrystalline WB4 outperforms the commercial Pt/C at high current density region, confirming potential applications in industrially electrochemical water splitting. Theoretical study reveals that high intrinsic HER activity of WB4 is originated from its large work function that contributes to the weak hydrogen-adsorption energy. Therefore, this work provides new insights for development of robust nanocrystalline electrocatalysts for efficient HER.

Transition metals-based electrocatalysts on super-flat substrate for perovskite photovoltaic hydrogen production with 13.75% solar to hydrogen efficiency.

Harnessing the inexhaustible solar energy for water splitting is regarded one of the most promising strategies for hydrogen production. However, sluggish kinetics of oxygen evolution reaction (OER) and expensive photovoltaics have hindered commercial viability. Here, an adhesive-free electrodeposition process is developed for in-situ preparation of earth-abundant electrocatalysts on super-flat indium tin oxide (ITO) substrate. NiFe hydroxide exhibited prominent OER performance, achieving an ultra-low overpotential of 236 mV at 10 mA/cm2 in alkaline solution. With the superior OER activity, we achieved an unassisted solar water splitting by series connected perovskite solar cells (PSCs) of 2 cm2 aperture area with NiFe/ITO//Pt electrodes, yielding overall solar to hydrogen (STH) efficiency of 13.75 %. Furthermore, we upscaled the monolithic facility to utilize perovskite solar module for large-scale hydrogen production and maintained an approximate operating current of 20 mA. This creative strategy contributes to the decrease of industrial manufacturing expenses for perovskite-based photovoltaic-electrochemical (PV-EC) hydrogen production, further accelerating the conversion and utilization of carbon-free energy.

Synergistic engineering of heterostructure and oxygen vacancy in cobalt hydroxide/aluminum oxyhydroxide as bifunctional electrocatalysts for urea-assisted hydrogen production.

Designing inexpensive, high-efficiency and durable bifunctional catalysts for urea oxidation reaction (UOR) and hydrogen evolution reaction (HER) is an encouraging tactic to produce hydrogen with reduced energy expenditure. Herein, oxygen vacancy-rich cobalt hydroxide/aluminum oxyhydroxide heterostructure on nickel foam (denoted as Co(OH)2/AlOOH/NF-100) has been fabricated using one step hydrothermal process. Theoretical calculation and experimental results indicate the electrons transfer from Co(OH)2 to highly active AlOOH results in the interfacial charge redistribution and optimization of electronic structure. Abundant oxygen vacancies in the heterostructure could improve the conductivity and simultaneously serve as the active sites for catalytic reaction. Consequently, the optimal Co(OH)2/AlOOH/NF-100 demonstrates excellent electrocatalytic performance for HER (62.9 mV@10 mA cm-2) and UOR (1.36 V@10 mA cm-2) due to the synergy between heterointerface and oxygen vacancies. Additionally, the in situ electrochemical impedance spectrum (EIS) for UOR suggests that the heterostructured catalyst exhibits rapid reaction kinetics, mass transfer and current response. Importantly, the urea-assisted electrolysis composed of the Co(OH)2/AlOOH/NF-100 manifests a low cell voltage (1.48 V @ 10 mA cm-2) in 1 M KOH containing 0.5 M urea. This work presents a promising avenue to the development of HER/UOR bifunctional electrocatalysts.

Conversion of Nitrate to Ammonia by Amidinothiourea-Coordinated Metal Molecular Electrocatalysts with d-π Conjugation.

The electrochemical reduction of nitrate to ammonia (NO3RR) provides a desired alternative of the traditional Haber-Bosch route for ammonia production, igniting a research boom in the development of electrocatalysts with high activity. Among them, molecular electrocatalysts hold considerable promise for the NO3RR, suppressing the competing hydrogen evolution reaction. However, the complicated synthesis procedure, usage of environmentally unfriendly organic solvents, and poor stability of Cu-based molecular electrocatalysts greatly limit their employment in NO3RR, and the development of desired Cu-based molecular catalysts remains challenging. Herein, a simple nonorganic solvent involving a one-step strategy was proposed to synthesize d-π-conjugated molecular electrocatalysts metal-amidinothiourea (M-ATU). Cu-ATU is composed of Cu coordinated with two S and two N atoms, whereas Ni-ATU is formed by Ni with four N atoms from two ATU ligands. Remarkably, Cu-ATU with a Cu-N2S2 coordination configuration exhibits superior NO3RR activity with a NH3 yield rate of 159.8 mg h-1 mgcat-1 (-1.54 V) and Faradaic efficiency of 91.7% (-1.34 V), outperforming previously reported molecular catalysts. Compared to Ni-ATU, Cu-ATU transfers more electrons to the *NO intermediate, effectively breaking the strong sp2 hybridization system and weakening the energy of N═O bonds. The increase in free energy of *NO reduced the energy barriers of the rate-determining step, facilitating the further hydrogenation process over Cu-ATU. Our work opened up a new horizon for exploring molecular electrocatalysts for nitrate activation and paved a way for the in-depth understanding of catalytic behaviors, aligning more closely with industrial demands.

Rationally Designed Mo/Ru-Based Multi-Site Heterogeneous Electrocatalyst for Accelerated Alkaline Hydrogen Evolution Reaction.

The rational design of multi-site electrocatalysts with three different functions for facile H2O dissociation, H-H coupling, and rapid H2 release is desirable but difficult to achieve. This strategy can accelerate the sluggish kinetics of the hydrogen evolution reaction (HER) under alkaline conditions. To resolve this issue, a Mo/Ru-based catalyst with three different active sites (Ru/Mo2C/MoO2) is rationally designed and its performance in alkaline HER is evaluated. The experimental results and density functional theory calculations revealed that, at the heterogeneous Mo2C/MoO2 interface, the higher valence state of Mo (MoO2) and the lower valence state of Mo (Mo2C) exhibited strong OH- and H-binding energies, respectively, which accelerated H2O dissociation. Moreover, the interfacial Ru possessed an appropriate hydrogen binding energy for H-H coupling and subsequent H2 evolution. Thus, this catalyst significantly accelerated the Volmer step and the Tafel step and, consequently, HER kinetics. This catalyst also demonstrated low overpotentials of 19 and 160 mV at current densities of 10 and 1000 mA cm-2, respectively, in alkaline media and long-term stability superior to that of most state-of-the-art alkaline HER electrocatalysts. This work provides a rational design principle for advanced multi-site catalytic systems, which can realize multi-electron electrocatalytic reactions.

Single-Step PECVD Synthesis of Graphene@Carbon Nanotubes Electrocatalyst.

Graphene (Gr) and carbon nanotubes (CNTs), the two intriguing carbon nanomaterials, have presented great potential in serving as high-performance electrocatalysts in lithium-sulfur (Li-S) chemistry. The concurrent management of both materials would achieve a promoted synergistic effect. Nevertheless, there still remains a lack of an effective material synthesis route. Herein, a single-step plasma-enhanced chemical vapor deposition (PECVD) strategy is devised to prepare Gr@CNTs heterostructures with strong bonded connections. In the PECVD system, the damaged sidewalls generated in CNT tubes can serve as appropriate nucleation sites for further Gr growth. The formation mechanisms are thoroughly explored in aspects of both experimental characterizations and theoretical calculations. To confirm the validity of this approach, thus-constructed Gr@CNTs architectures are employed as the sulfur host, enabling boosted redox kinetics of polysulfides. This project provides fundamental insight into the mechanism exploration for single-step PECVD growth of Gr@CNTs heterostructure, hence promoting the practical application prospect of carbon nanomaterials toward Li-S systems.

NiIr nanowire assembles as an efficient electrocatalyst towards oxygen evolution reaction in both acid and alkaline media.

Oxygen evolution reaction (OER) is the rate-limiting step in water electrolysis due to its sluggish kinetic, and it is challenging to develop an OER catalyst that could work efficiently in both acid and alkaline environment. Herein, NiIr nanowire assembles (NAs) with unique nanoflower morphology were prepared by a facile hydrothermal method. As a result, the NiIr NAs exhibited superior OER activity in both acid and alkaline media. Specifically, in 0.1 M HClO4, NiIr NAs presented a superior electrocatalytic performance with a low overpotential of merely 242 mV at 10 mA cm-2 and a Tafel slope of only 58.1 mV dec-1, surpassing that of commercial IrO2 and pure Ir NAs. And it achieved a significantly higher mass activity of 148.40 A/g at -1.5 V versus RHE. In 1.0 M KOH, NiIr NAs has an overpotential of 291 mV at 10 mA cm-2 and a Tafel slope of 42.1 mV dec-1. Such remarkable activity makes the NiIr NAs among the best of recently reported representative Ir-based OER electrocatalysts. Density functional theory (DFT) calculations confirmed alloying effect promotes surface bonding of NiIr with oxygen-containing reactants, resulting in excellent catalytic properties.

Rational Strategies for Preparing Highly Efficient Tin-, Bismuth- or Indium Based Electrocatalysts for Electrochemical CO2 Reduction to Formic acid.

Electrochemical carbon dioxide reduction reaction (CO2RR) is an environmentally friendly and economically viable approach to convert greenhouse gas CO2 into valuable chemical fuels and feedstocks. Among various products of CO2RR, formic acid/formate (HCOOH/HCOO-) is considered the most attractive one with its high energy density and ease of storage, thereby enabling widespread commercial applications in chemical, medicine, and energy-related industries. Nowadays, the development of efficient and financially feasible electrocatalysts with excellent selectivity and activity towards HCOOH/HCOO- is paramount for the industrial application of CO2RR technology, in which Tin (Sn), Bismuth (Bi), and Indium (In)-based electrocatalysts have drawn significant attention due to their high efficiency and various regulation strategies have been explored to design diverse advanced electrocatalysts. Herein, we comprehensively review the rational strategies to enhance electrocatalytic performances of these electrocatalysts for CO2RR to HCOOH/HCOO-. Specifically, the internal mechanism between the physicochemical properties of engineering materials and electrocatalytic performance is analyzed and discussed in details. Besides, the current challenges and future opportunities are proposed to provide inspiration for the development of more efficient electrocatalysts in this field.

Unveiling the Dual Role of Oxophilic Cr4+ in Cr-Cu2O Nanosheet Arrays for Enhanced Nitrate Electroreduction to Ammonia.

Cuprous oxide (Cu2O)-based catalysts present a promising activity for the electrochemical nitrate (NO3-) reduction to ammonia (eNO3RA), but the electrochemical instability of Cu+ species may lead to an unsatisfactory durability, hindering the exploration of the structure-performance relationship. Herein, we propose an efficient strategy to stabilize Cu+ through the incorporation of Cr4+ into the Cu2O matrix to construct a Cr4+-O-Cu+ network structure. In situ and quasi-in situ characterizations reveal that the Cu+ species are well maintained via the strong Cr4+-O-Cu+ interaction that inhibits the leaching of lattice oxygen. Importantly, in situ generated Cr3+-O-Cu+ from Cr4+-O-Cu+ is identified as a dual-active site for eNO3RA, wherein the Cu+ sites are responsible for the activation of N-containing intermediates, while the assisting Cr3+ centers serve as the electron-proton mediators for rapid water dissociation. Theoretical investigations further demonstrated that the metastable state Cr3+-O-Cu+ favors the conversion from the endoergic hydrogenation of the key *ON intermediate to an exoergic reaction in an ONH pathway, and facilitates the subsequent NH3 desorption with a low energy barrier. The superior eNO3RA with a maximum 91.6% Faradaic efficiency could also be coupled with anodic sulfion oxidation to achieve concurrent NH3 production and sulfur recovery with reduced energy input.

Partially Amorphous Ru-Doped CoSe Nanoparticles with Optimized Intermediates Adsorption for Highly Efficient Sulfur Oxidation Reaction.

The application of thermodynamically more favorable sulfur oxidation reaction (SOR) to replace oxygen evolution reaction (OER) in electrocatalytic water electrolysis is an appealing strategy to achieve low-energy hydrogen production while removing toxic sulfur ions from wastewater. However, the study of SOR catalysts with both activity and stability still faces great challenges. Herein, this study prepares partially amorphous Ru-doped CoSe (pa-Ru-CoSe) nanoparticles for SOR. The doping of Ru keeps Co in an electron-deficient state, which enhances the adsorption of SOR intermediates and improves the catalytic activity. Meanwhile, the partially amorphous selenide possesses great corrosion resistance to sulfur species, thus ensuring stability in long-term SOR. In addition, the pa-Ru-CoSe requires only 0.566 V to reach a current density of 100 mA cm-2 in the SOR-HER coupled system and remains stable for 200 h. This work provides a promising partially amorphous strategy for SOR catalysts with both catalytic activity and long-term stability, enabling hydrogen production with low energy consumption and simultaneous sulfur production.

Structural Modification Effect of Se-doped Porous Carbon for Hydrogen Evolution Coupled Selective Electrooxidation of Ethylene Glycol to Value-added Glycolic Acid.

The ethylene glycol oxidation reaction (EGOR) has attracted attention because ethylene glycol (EG), which exhibits large-scale production and a low market price, can be reformed into valuable glycolic acid (GCA) with the cogeneration of high-purity hydrogen gas during the reaction. In this study, a noble catalyst material of Pt nanoparticles supported on Se-doped porous carbon (Pt/SePC) is prepared and investigated for the selective electrochemical oxidation of EG to GCA. Pt/SePC achieved a maximum EG conversion of 94.6% and GCA selectivity of 84.4% and maintained this high performance with negligible degradation during durability tests. Furthermore, the EGOR required lower overpotential rather than the oxygen evolution reaction, thus the EGOR coupled with the hydrogen evolution reaction can reduce the cell overpotential to 0.60 V, which is much lower than that of water electrolysis (1.58 V). The effect of Se doping is investigated through experimental analyses and density functional theory (DFT) calculations, and they shows that Se modified the binding energy of Pt nanoparticles and the adsorption energy of reactants by lattice deformation and charge density modification. This study provides scientific insights and strategies for electrocatalyst design for the selective oxidation of polyols to value-added chemicals via the cogeneration of hydrogen gas.

Bimetallic Sulfur-Doped Nickel-Cobalt Selenides as Efficient Bifunctional Electrocatalysts for the Complete Decomposition of Water.

The creation and enhancement of non-precious metal bifunctional catalysts with superior stability and stabilizing activity is necessary to achieve water splitting in alkaline media. The paper presents a method for preparing nickel-cobalt bimetallic selenides (NiCo-Sex/CF) using a combination of hydrothermal and high-temperature selenization techniques. NiCo-Sex/CF shows great potential as a catalyst for water separation. The catalyst's electronic structure and active centre can be modified by double doping with sulfur and selenium, resulting in increased selectivity and activity under varying reaction conditions. This method also offers the benefits of a simple preparation process and applicability to a wide range of catalytic reactions. Experimental results demonstrate that an overpotential of 194 mV produces a current density of 10 mA cm-2 when using this electrocatalyst as an OER catalyst. When used as a HER catalyst, the electrocatalyst required an overpotential of only 76 mV to generate a current density of 10 mA cm-2.Furthermore, a voltage of 1.5 V can drive the overall decomposition of water to achieve a current density of 10 mA cm-2. This study highlights the potential of sulfur-selenide double-doped catalysts for both scientific research and practical applications.

Interfacial coupling of Ce-CoSe2 nanoneedle arrays with MXene for efficient overall water splitting.

Designing highly effective, low-cost bifunctional electrocatalysts without noble metals for overall water splitting remains a significant challenge. In this work, interfacial coupling of Ce-doped CoSe2 nanoneedle arrays with MXene (Ce-CoSe2/MXene) is developed via the facile hydrothermal and selenization methods. The extensive specific surface area and favorable hydrophilicity of Ti3AlC2, combined with the optimized electronic structure and abundant active sites from Ce-doping and selenization, contribute to the exceptional bifunctional electrocatalytic performance of the Ce-CoSe2/MXene electrode. Specifically, this heterostructure achieves a low hydrogen evolution reaction (HER) overpotential of 34 mV at 10 mA cm-2, an oxygen evolution reaction (OER) overpotential of 279 mV at 100 mA cm-2, and an overall water splitting (OWS) potential as low as 1.45 V at 10 mA cm-2. In-situ Raman spectroscopy reveals that surface reconstruction would improve catalytic activity and stability. Theoretical calculations indicate that the Ce-CoSe2/MXene can improve the adsorption of intermediates and facilitate HER/OER process by lowering the kinetic barrier, thereby enhancing electrocatalytic activity. This research marks a substantial advancement in the development of low-cost, efficient electrocatalysts for overall water splitting.

Modulating the D-Band Center of Electrocatalysts for Enhanced Water Splitting.

To tackle the global energy scarcity and environmental degradation, developing efficient electrocatalysts is essential for achieving sustainable hydrogen production via water splitting. Modulating the d-band center of transition metal electrocatalysts is an effective approach to regulate the adsorption energy of intermediates, alter reaction pathways, lower the energy barrier of the rate-determining step, and ultimately improve electrocatalytic water splitting performance. In this review, a comprehensive overview of the recent advancements in modulating the d-band center for enhanced electrocatalytic water splitting is offered. Initially, the basics of the d-band theory are discussed. Subsequently, recent modulation strategies that aim to boost electrocatalytic activity, with particular emphasis on the d-band center as a key indicator in water splitting are summarized. Lastly, the importance of regulating electrocatalytic activity through d-band center, along with the challenges and prospects for improving electrocatalytic water splitting performance by fine-tuning the transition metal d-band center, are provided.

Electrocatalytic ethanol oxidation reaction: recent progress, challenges, and future prospects.

Direct ethanol fuel cells (DEFCs) have been widely considered as a feasible power conversion technology for portable and mobile applications. The economic feasibility of DEFCs relies on two conditions: a notable reduction in the expensive nature of precious metal electrocatalysts and a simultaneous remarkable improvement in the anode's long-term performance. Despite the considerable progress achieved in recent decades in Pt nanoengineering to reduce its loading in catalyst ink with enhanced mass activity, attempts to tackle these problems have yet to be successful. During the ethanol oxidation reaction (EOR) at the anode surface, Pt electrocatalysts lose their electrocatalytic activity rapidly due to poisoning by surface-adsorbed reaction intermediates like CO. This phenomenon leads to a significant loss in electrocatalytic performance within a relatively short time. This review provides an overview of the mechanistic approaches during the EOR of noble metal-based anode materials. Additionally, we emphasized the significance of many essential factors that govern the EOR activity of the electrode surface. Furthermore, we provided a comprehensive examination of the challenges and potential advancements in electrocatalytic EOR.

A Long-Range Disordering RuO2 Catalyst for Highly Efficient Acidic Oxygen Evolution Electrocatalysis.

Non-iridium acid-stabilized electrocatalysts for oxygen evolution reaction (OER) are crucial to reducing the cost of proton exchange membrane water electrolyzers (PEMWEs). Here, we report a strategy to modulate the stability of RuO2 by doping boron (B) atoms, leading to the preparation of a RuO2 catalyst with long-range disorder (LD-B/RuO2). The structure of long-range disorder endowed LD-B/RuO2 with a low overpotential of 175 mV and an ultra-long stability, which can maintain OER for about 1.6 months at 10 mA cm-2 current density in 0.5 M H2SO4 with almost invariable performance. More importantly, a PEM electrolyzer using LD-B/RuO2 as the anode demonstrated excellent performance, reaching 1000 mA cm-2 at 1.63 V with durability exceeding 300 h at 250 mA cm-2 current density. The introduction of B atoms induced the formation of a long-range disordered structure and symmetry-breaking B-Ru-O motifs, which enabled the catalyst structure to a certain toughness while simultaneously inducing the redistribution of electrons on the active center Ru, which jointly promoted and guaranteed the activity and long-term stability of LD-B/RuO2. This study provides a strategy to prepare long-range disordered RuO2 acidic OER catalysts with high stability using B-doping to perturb crystallinity, which opens potential possibilities for non-iridium-based PEMWE applications.

Electronic Engineering of Crystalline/Amorphous CoP/FeCoPx Nanoarrays for Efficient Water Electrolysis.

The development of bifunctional, non-noble metal-based electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) through morphology and electronic engineering is highly attractive for efficient water splitting. Herein, hierarchical nanoarrays consisting of crystalline cobalt phosphide nanorods covered by amorphous Fe-doped cobalt phosphide nanocuboids (CoP/FeCoPx) are constructed as bifunctional catalysts for both HER and OER. Experimental results and theoretical calculations reveal that the catalysts exhibit balanced dual-catalytic properties due to simultaneous introduction of Fe doping and phosphorus vacancies, leading to an optimized electronic structure of the CoP/FeCoPx. Furthermore, the hierarchical nanoarrays made of crystalline/amorphous heterostructures significantly enhance the performance of the electrocatalysts. As a result, the CoP/FeCoPx catalyst demonstrates remarkable performance in both HER and OER, with overpotentials of 74 and 237 mV at 10 mA cm-2 in 1 m KOH, respectively, as well as a low cell voltage of 1.53 V at 10 mA cm-2 for alkaline overall water splitting. This work integrates the morphology engineering involving design of hierarchical crystalline/amorphous nanoarrays and the electronic engineering through Fe doping and phosphorus vacancies for efficient water electrolysis. It may open a new route toward rational design and feasible fabrication of high-performance, multifunctional, non-noble metal-based electrocatalysts for energy conversion.

Nanoarchitectonics of Fe-Doped Ni3S2 Arrays on Ni Foam from MOF Precursors for Promoted Oxygen Evolution Reaction Activity.

Oxygen evolution reaction (OER) is a critical half-reaction in electrochemical overall water splitting and metal-air battery fields; however, the exploitation of the high activity of non-noble metal electrocatalysts to promote the intrinsic slow kinetics of OER is a vital and urgent research topic. Herein, Fe-doped Ni3S2 arrays were derived from MOF precursors and directly grown on nickel foam via the traditional solvothermal way. The arrays integrated into nickel foam can be used as self-supported electrodes directly without any adhesive. Due to the synergistic effect of Fe and Ni elements in the Ni3S2 structure, the optimized Fe2.3%-Ni3S2/NF electrode delivers excellent OER activity in an alkaline medium. The optimized electrode only requires a small overpotential of 233 mV to reach the current density of 10 mA cm-2, and the catalytic activity of the electrode can surpass several related electrodes reported in the literature. In addition, the long-term stability of the Fe2.3%-Ni3S2/NF electrode showed no significant attenuation after 12 h of testing at a current density of 50 mA cm-2. The introduction of Fe ions could modulate the electrical conductivity and morphology of the Ni3S2 structure and thus provide a high electrochemically active area, fast reaction sites, and charge transfer rate for OER activity.