Promoting Active Sites in Core–Shell Nanowire Array as Mott–Schottky Electrocatalysts for Efficient and Stable Overall Water Splitting

Developing earth‐abundant, active, and robust electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) remains a vital challenge for efficient conversion of sustainable energy sources. Herein, metal–semiconductor hybrids are reported with metallic nanoalloys on various defective oxide nanowire arrays (Cu/CuO_x, Co/CoO_x, and CuCo/CuCoO_x) as typical Mott–Schottky electrocatalysts. To build the highway of continuous electron transport between metals and semiconductors, nitrogen‐doped carbon (NC) has been implanted on metal–semiconductor nanowire array as core–shell conductive architecture. As expected, NC/CuCo/CuCoO_x nanowires arrays, as integrated Mott–Schottky electrocatalysts, present an overpotential of 112 mV at 10 mA cm^?2 and a low Tafel slope of 55 mV dec^?1 for HER, simultaneously delivering an overpotential of 190 mV at 10 mA cm^?2 for OER. Most importantly, NC/CuCo/CuCoO_x architectures, as both the anode and the cathode for overall water splitting, exhibit a current density of 10 mA cm^?2 at a cell voltage of 1.53 V with excellent stability due to high conductivity, large active surface area, abundant active sites, and the continuous electron transport from prominent synergetic effect among metal, semiconductor, and nitrogen‐doped carbon. This work represents an avenue to design and develop efficient and stable Mott–Schottky bifunctional electrocatalysts for promising energy conversion.     

Metal‐Organic Frameworks Derived Nanotube of Nickel–Cobalt Bimetal Phosphides as Highly Efficient Electrocatalysts for Overall Water Splitting

The design of highly efficient, stable, and noble‐metal‐free bifunctional electrocatalysts for overall water splitting is critical but challenging. Herein, a facile and controllable synthesis strategy for nickel–cobalt bimetal phosphide nanotubes as highly efficient electrocatalysts for overall water splitting via low‐temperature phosphorization from a bimetallic metal‐organic framework (MOF‐74) precursor is reported. By optimizing the molar ratio of Co/Ni atoms in MOF‐74, a series of Cox Niy P catalysts are synthesized, and the obtained Co4Ni1P has a rare form of nanotubes that possess similar morphology to the MOF precursor and exhibit perfect dispersal of the active sites. The nanotubes show remarkable hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) catalytic performance in an alkaline electrolyte, affording a current density of 10 mA cm^?2 at overpotentials of 129 mV for HER and 245 mV for OER, respectively. An electrolyzer with Co4Ni1P nanotubes as both the cathode and anode catalyst in alkaline solutions achieves a current density of 10 mA cm^?2 at a voltage of 1.59 V, which is comparable to the integrated Pt/C and RuO₂ counterparts and ranks among the best of the metal‐phosphide electrocatalysts reported to date.     

Self‐Powered Water‐Splitting Devices by Core–Shell NiFe@N‐Graphite‐Based Zn–Air Batteries

Development of highly efficient and low‐cost multifunctional electrocatalysts for the oxygen evolution reaction (OER), the oxygen reduction reaction (ORR), and the hydrogen evolution reaction is urgently required for energy storage and conversion applications, such as in Zn–air batteries and water splitting to replace very expansive noble metal catalysts. Here, the new core–shell NiFe@N‐graphite electrocatalysts with excellent electrocatalytic activity and stability toward OER and ORR are reported and the Ni_0.5Fe_0.5@N‐graphite electrocatalyst is applied as the air electrode in Zn–air batteries. The respective liquid Zn–air battery shows a large open‐circuit potential of 1.482 V and a small charge–discharge voltage gap of 0.12 V at 10 mA cm⁻², together with excellent cycling stability even after 40 h at 20 mA cm⁻². Interestingly, the all‐solid‐like Zn–air battery thus derived shows a highly desired mechanical flexibility, whereby little change is observed in the voltage when bent into different angles. Using the same Ni_0.5Fe_0.5@N‐graphite electrode, a self‐driven water‐splitting device, which is powered by two Zn–air batteries in‐series, is constructed. The present study opens a new opportunity for the rational design of metal@N‐graphite‐based catalysts of core–shell structures for electrochemical catalysts and renewable energy applications.     

Engineering an Earth‐Abundant Element‐Based Bifunctional Electrocatalyst for Highly Efficient and Durable Overall Water Splitting

The simultaneous and efficient evolution of hydrogen and oxygen with earth‐abundant, highly active, and robust bifunctional electrocatalysts is a significant concern in water splitting. Herein, non‐noble metal‐based Ni–Co–S bifunctional catalysts with tunable stoichiometry and morphology are realized. The engineering of electronic structure and subsequent morphological design synergistically contributes to significantly elevated electrocatalytic performance. Stable overpotentials (η₁₀) of 243 mV (vs reversible hydrogen electrode) for oxygen evolution reaction (OER) and 80 mV for hydrogen evolution reaction (HER), as well as Tafel slopes of 54.9 mV dec^?1 for OER and 58.5 mV dec^?1 for HER, are demonstrated. In addition, density functional theory calculations are performed to determine the optimal electronic structure via the electron density differences to verify the enhanced OER activity is related to the Co top site on the (110) surface. Moreover, the tandem bifunctional NiCo₂S₄ exhibit a required voltage of 1.58 V (J = 10 mA cm^?2) for simultaneous OER and HER, and no obvious performance decay is observed after 72 h. When integrated with a GaAs solar cell, the resulting photoassisted water splitting electrolyzer shows a certified solar‐to‐hydrogen efficiency of up to 18.01%, further demonstrating the feasibility of engineering protocols and the promising potential of bifunctional NiCo₂S₄ for large‐scale overall water splitting.     

Efficient Optimization of Electron/Oxygen Pathway by Constructing Ceria/Hydroxide Interface for Highly Active Oxygen Evolution Reaction

Owing to the unique electronic properties, rare‐earth modulations in noble‐metal electrocatalysts emerge as a critical strategy for a broad range of renewable energy solutions such as water‐splitting and metal–air batteries. Beyond the typical doping strategy that suffers from synthesis difficulties and concentration limitations, the innovative introduction of rare‐earth is highly desired. Herein, a novel synthesis strategy is presented by introducing CeO₂ support for the nickel–iron–chromium hydroxide (NFC) to boost the oxygen evolution reaction (OER) performance, which achieves an ultralow overpotential at 10 mA cm^?2 of 230.8 mV, the Tafel slope of 32.7 mV dec^?1, as well as the excellent durability in alkaline solution. Density functional theory calculations prove the established d–f electronic ladders, by the interaction between NFC and CeO₂, evidently boosts the high‐speed electron transfer. Meanwhile, the stable valence state in CeO₂ preserves the high electronic reactivity for OER. This work demonstrates a promising approach in fabricating a nonprecious OER electrocatalyst with the facilitation of rare‐earth oxides to reach both excellent activity and high stability.     

Fabrication of Nickel–Cobalt Bimetal Phosphide Nanocages for Enhanced Oxygen Evolution Catalysis

Replacement of precious metals with earth‐abundant electrocatalysts for oxygen evolution reaction (OER) holds great promise for realizing practically viable water‐splitting systems. It still remains a great challenge to develop low‐cost, highly efficient, and durable OER catalysts. Here, the composition and morphology of Ni–Co bimetal phosphide nanocages are engineered for a highly efficient and durable OER electrocatalyst. The nanocage structure enlarges the effective specific area and facilitates the contact between catalyst and electrolyte. The as‐prepared Ni–Co bimetal phosphide nanocages show superior OER performance compared with Ni₂P and CoP nanocages. By controlling the molar ratio of Ni/Co atoms in Ni–Co bimetal hydroxides, the Ni_0.6Co_1.4P nanocages derived from Ni_0.6Co_1.4(OH)₂ nanocages exhibit remarkable OER catalytic activity (η = 300 mV at 10 mA cm^?2) and long‐term stability (10 h for continuous test). The density‐functional‐theory calculations suggest that the appropriate Co doping concentration increases density of states at the Fermi level and makes the d‐states more close to Fermi level, giving rise to high charge carrier density and low intermedia adsorption energy than those of Ni₂P and CoP. This work also provides a general approach to optimize the catalysis performance of bimetal compounds.     

CuCo Hybrid Oxides as Bifunctional Electrocatalyst for Efficient Water Splitting

Solar‐driven water splitting is a promising approach for renewable energy, where the development of efficient and stable bifunctional electrocatalysts for simultaneously producing hydrogen and oxygen is still challenging. Herein, combined with the hydrogen evolution reaction (HER) activity of a copper(I) complex and oxygen evolution reaction (OER) activity of cobalt‐based oxides, a type of 1D copper‐cobalt hybrid oxide nanowires (CuCoO‐NWs) is developed via a facile two‐step growth‐conversion process toward a bifunctional water splitting catalyst. The CuCoO‐NWs exhibit excellent catalytic performances for both HER and OER in the same basic electrolyte, with optimized low onset overpotentials and high current densities. The efficient HER activity is ascribed to the formation of Cu₂O, while the activity for OER is primarily enabled by Co‐based oxides and abundant oxygen vacancies. The CuCoO‐NWs allow for the assembly of a water electrolyzer with strong alkaline media, with a current density of 10 mA cm^?2 at 1.61 V. Further combination with a commercial silicon photovoltaic allows the direct use of solar energy for spontaneous water splitting with excellent stability for over 72 h, suggesting the potential as a promising bifunctional electrocatalyst for efficient solar‐driven water splitting.     

Etching‐Doping Sedimentation Equilibrium Strategy: Accelerating Kinetics on Hollow Rh‐Doped CoFe‐Layered Double Hydroxides for Water Splitting

Exploring highly active and inexpensive bifunctional electrocatalysts for water‐splitting is considered to be one of the prerequisites for developing hydrogen energy technology. Here, an efficient simultaneous etching‐doping sedimentation equilibrium (EDSE) strategy is proposed to design and prepare hollow Rh‐doped CoFe‐layered double hydroxides for overall water splitting. The elaborate electrocatalyst with optimized composition and typical hollow structure accelerates the electrochemical reactions, which can achieve a current density of 10 mA cm^?2 at an overpotential of 28 mV (600 mA cm^?2 at 188 mV) for hydrogen evolution reaction (HER) and 100 mA cm^?2 at 245 mV for oxygen evolution reaction (OER). The cell voltage for overall water splitting of the electrolyzer assembled by this electrocatalyst is only 1.46 V, a value far lower than that of commercial electrolyzer constructed by Pt/C and RuO₂ and most reported bifunctional electrocatalysts. Furthermore, the existence of Fe vacancies introduced by Rh doping and the typical hollow structure are demonstrated to optimize the entire HER and OER processes. EDSE associates doping with template‐directed hollow structures and paves a new avenue for developing bifunctional electrocatalysts for overall water splitting. It is also believed to be practical in other catalysis fields as well.     

High‐Performance Metal‐Free Nanosheets Array Electrocatalyst for Oxygen Evolution Reaction in Acid

Development of low cost electrocatalysts with outstanding catalytic activity and stability for oxygen evolution reaction (OER) in acid is a major challenge to produce hydrogen energy from water splitting. Herein, a novel metal‐free electrocatalyst consisting of a oxygen‐functionalized electrochemically exfoliated graphene (OEEG) nanosheets array is reported. Benefitting from a vertically aligned arrays structure and introducing oxygen functional groups, the metal‐free OEEG nanosheets array exhibits superior electrocatalytic activity and stability toward OER with a low overpotential of 334 mV at 10 mA cm^?2 in acidic electrolyte. Such a high OER performance is thus far the best among all previously reported metal‐free carbon‐based materials, and even superior to commercial Ir/C catalysts (420 mV at 10 mA cm^?2) in acid. Characterization results and electrochemical measurements identify the COOH species in the OEEG acting as active sites for acidic OER, which is further supported by atomic‐scale scanning transmission electron microscopy imaging and electron energy‐loss spectroscopy. Density functional theory calculations reveal that the reaction pathway of dual sites that is mixed by zigzag and armchair edges (COOH‐zig‐corner) is better than the pathway of single site.     

Hierarchical Porous Ni3S4 with Enriched High‐Valence Ni Sites as a Robust Electrocatalyst for Efficient Oxygen Evolution Reaction

Electrochemical water splitting is a common way to produce hydrogen gas, but the sluggish kinetics of the oxygen evolution reaction (OER) significantly limits the overall energy conversion efficiency of water splitting. In this work, a highly active and stable, meso–macro hierarchical porous Ni₃S₄ architecture, enriched in Ni³⁺ is designed as an advanced electrocatalyst for OER. The obtained Ni₃S₄ architectures exhibit a relatively low overpotential of 257 mV at 10 mA cm^?2 and 300 mV at 50 mA cm^?2. Additionally, this Ni₃S₄ catalyst has excellent long‐term stability (no degradation after 300 h at 50 mA cm^?2). The outstanding OER performance is due to the high concentration of Ni³⁺ and the meso–macro hierarchical porous structure. The presence of Ni³⁺ enhances the chemisorption of OH^?, which facilitates electron transfer to the surface during OER. The hierarchical porosity increases the number of exposed active sites, and facilitates mass transport. A water‐splitting electrolyzer using the prepared Ni₃S₄ as the anode catalyst and Pt/C as the cathode catalyst achieves a low cell voltage of 1.51 V at 10 mA cm^?2. Therefore, this work provides a new strategy for the rational design of highly active OER electrocatalysts with high valence Ni³⁺ and hierarchical porous architectures.     

Amorphous Cobalt–Iron Hydroxide Nanosheet Electrocatalyst for Efficient Electrochemical and Photo‐Electrochemical Oxygen Evolution

Finding efficient electrocatalysts for oxygen evolution reaction (OER) that can be effectively integrated with semiconductors is significantly challenging for solar‐driven photo‐electrochemical (PEC) water splitting. Herein, amorphous cobalt–iron hydroxide (CoFe? H) nanosheets are synthesized by facile electrodeposition as an efficient catalyst for both electrochemical and PEC water oxidation. As a result of the high electrochemically active surface area and the amorphous nature, the optimized amorphous CoFe? H nanosheets exhibit superior OER catalytic activity in alkaline environment with a small overpotential (280 mV) to achieve significant oxygen evolution (j = 10 mA cm^?2) and a low Tafel slope (28 mV dec^?1). Furthermore, CoFe? H nanosheets are simply integrated with BiVO₄ semiconductor to construct CoFe? H/BiVO₄ photoanodes that exhibit a significantly enhanced photocurrent density of 2.48 mA cm^?2 (at 1.23 V vs reversible hydrogen electrode (RHE)) and a much lower onset potential of 0.23 V (vs RHE) for PEC‐OER. Careful electrochemical and optical studies reveal that the improved OER kinetics and high‐quality interface at the CoFe? H/BiVO₄ junction, as well as the excellent optical transparency of CoFe? H nanosheets, contribute to the high PEC performance. This study establishes amorphous CoFe? H nanosheets as a highly competitive candidate for electrochemical and PEC water oxidation and provides general guidelines for designing efficient PEC systems.     

Electro‐Oxidation of Ni42 Steel: A Highly Active Bifunctional Electrocatalyst

Janus type water‐splitting catalysts have attracted highest attention as a tool of choice for solar to fuel conversion. AISI Ni42 steel is upon harsh anodization converted into a bifunctional electrocatalyst. Oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are highly efficiently and steadfast catalyzed at pH 7, 13, 14, 14.6 (OER) and at pH 0, 1, 13, 14, 14.6 (HER), respectively. The current density taken from long‐term OER measurements in pH 7 buffer solution upon the electro‐activated steel at 491 mV overpotential (η) is around four times higher (4 mA cm^?2) in comparison with recently developed OER electrocatalysts. The very strong voltage–current behavior of the catalyst shown in OER polarization experiments at both pH 7 and at pH 13 are even superior to those known for IrO₂‐RuO₂. No degradation of the catalyst is detected even when conditions close to standard industrial operations are applied to the catalyst. A stable Ni‐, Fe‐oxide based passivating layer sufficiently protects the bare metal for further oxidation. Quantitative charge to oxygen (OER) and charge to hydrogen (HER) conversion are confirmed. High‐resolution XPS spectra show that most likely γ?NiO(OH) and FeO(OH) are the catalytic active OER and NiO is the catalytic active HER species.     

Regulating the Electronic Structure of CoP Nanosheets by O Incorporation for High‐Efficiency Electrochemical Overall Water Splitting

The exploration of earth‐abundant and high‐efficiency bifunctional electrocatalysts for overall water splitting is of vital importance for the future of the hydrogen economy. Regulation of electronic structure through heteroatom doping represents one of the most powerful strategies to boost the electrocatalytic performance of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, a rational design of O‐incorporated CoP (denoted as O‐CoP) nanosheets, which synergistically integrate the favorable thermodynamics through modification of electronic structures with accelerated kinetics through nanostructuring, is reported. Experimental results and density functional theory simulations manifest that the appropriate O incorporation into CoP can dramatically modulate the electronic structure of CoP and alter the adsorption free energies of reaction intermediates, thus promoting the HER and OER activities. Specifically, the optimized O‐CoP nanosheets exhibit efficient bifunctional performance in alkaline electrolyte, requiring overpotentials of 98 and 310 mV to deliver a current density of 10 mA cm^?2 for HER and OER, respectively. When served as bifunctional electrocatalysts for overall water splitting, a low cell voltage of 1.60 V is needed for achieving a current density of 10 mA cm^?2. This proposed anion‐doping strategy will bring new inspiration to boost the electrocatalytic performance of transition metal–based electrocatalysts for energy conversion applications.     

Single-Atom Co-Decorated MoS2 Nanosheets Assembled on Metal Nitride Nanorod Arrays as an Efficient Bifunctional Electrocatalyst for pH-Universal Water Splitting

The commercialization of electrochemical water splitting technology requires electrocatalysts that are cost-effective, highly efficient, and stable. Herein, an advanced bifunctional electrocatalyst based on single-atom Co-decorated MoS₂ nanosheets grown on 3D titanium nitride (TiN) nanorod arrays (CoSAs-MoS₂/TiN NRs) has been developed for overall water splitting in pH-universal electrolytes. When applied as a self-standing cathodic electrode, the CoSAs-MoS₂/TiN NRs requires overpotentials of 187.5, 131.9, and 203.4 mV to reach a HER current density of 10 mA cm^–2 in acidic, alkaline, and neutral conditions, respectively, which are superior to the most previously reported non-noble metal HER electrocatalysts at the same current density. The CoSAs-MoS₂/TiN NRs anodic electrode also shows low OER overpotentials of 454.9, 340.6, and 508.0 mV, respectively, at a current density of 10 mA cm^–2 in acidic, alkaline, and neutral mediums, markedly outperforming current OER catalysts reported elsewhere. More importantly, an electrolyzer delivered from the cathodic and anodic CoSAs-MoS₂/TiN NRs electrodes exhibits an extraordinary overall water splitting performance with good stability and durability in pH-universal conditions.     

Electronic and Vacancy Engineering of Mo–RuCoOx Nanoarrays for High-Efficiency Water Splitting (Adv. Funct. Mater. 40/2023)

Exploring efficient strategies to achieve novel high-efficiency catalysts for water splitting is of great significance to develop hydrogen energy technology. Herein, unique molybdenum (Mo)-doped ruthenium–cobalt oxide (Mo–RuCoO_x) nanosheet arrays are prepared as a high-performance bifunctional electrocatalyst toward hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) through combining electronic and vacancy engineering. Theoretical calculations and experimental results reveal that the incorporation of Ru and Mo can effectively tune the electronic structure, and the controllable Mo dissolution coupling with the oxygen vacancy generation during surface reconstruction is able to optimize the adsorption energy of hydrogen/oxygen intermediates, thus greatly accelerating the kinetics for both HER and OER. As a result, the Mo–RuCoO_x nanoarrays exhibit remarkably low overpotentials of 41 and 156 mV at 10 mA cm⁻² for HER and OER in 1 m KOH, respectively. Furthermore, the two-electrode electrolyzer assembled by the Mo–RuCoO_x nanoarrays requires a cell voltage as low as 1.457 V to achieve 10 mA cm⁻² for alkaline overall water splitting. This work holds great promise to develop novel and highly active electrocatalysts for future energy conversion applications.     

Homologous CoP/NiCoP Heterostructure on N‐Doped Carbon for Highly Efficient and pH‐Universal Hydrogen Evolution Electrocatalysis

Hydrogen evolution electrocatalysts can achieve sustainable hydrogen production via electrocatalytic water splitting; however, designing highly active and stable noble‐metal‐free hydrogen evolution electrocatalysts that perform as efficiently as Pt catalysts over a wide pH range is a challenging task. Herein, a new 2D cobalt phosphide/nickelcobalt phosphide (CoP/NiCoP) hybrid nanosheet network is proposed, supported on an N‐doped carbon (NC) matrix as a highly efficient and durable pH‐universal hydrogen evolution reaction (HER) electrocatalyst. It is derived from topological transformation of corresponding layer double hydroxides and graphitic carbon nitride. This 2D CoP/NiCoP/NC catalyst exhibits versatile HER electroactivity with very low overpotentials of 75, 60, and 123 mV in 1 m KOH, 0.5 m H₂SO₄, and 1 m PBS electrolytes, respectively, delivering a current density of 10 mA cm^?2 for HER. Such impressive HER performance of the hybrid electrocatalyst is mainly attributed to the collective effects of electronic structure engineering, strong interfacial coupling between CoP and NiCoP in heterojunction, an enlarged surface area/exposed catalytic active sites due to the 2D morphology, and conductive NC support. This method is believed to provide a basis for the development of efficient 2D electrode materials with various electrochemical applications.     

Defect‐Rich Nitrogen Doped Co3O4/C Porous Nanocubes Enable High‐Efficiency Bifunctional Oxygen Electrocatalysis

Heteroatom doping plays a significant role in optimizing the catalytic performance of electrocatalysts. However, research on heteroatom doped electrocatalysts with abundant defects and well‐defined morphology remain a great challenge. Herein, a class of defect‐engineered nitrogen‐doped Co₃O₄ nanoparticles/nitrogen‐doped carbon framework (N‐Co₃O₄@NC) strongly coupled porous nanocubes, made using a zeolitic imidazolate framework‐67 via a controllable N‐doping strategy, is demonstrated for achieving remarkable oxygen evolution reaction (OER) catalysis. X‐ray photoelectron spectroscopy, X‐ray absorption fine structure, and electron spin resonance results clearly reveal the formation of a considerable amount of nitrogen dopants and oxygen vacancies in N‐Co₃O₄@NC. The defect engineering of N‐Co₃O₄@NC makes it exhibit an overpotential of only 266 mV to reach 10 mA cm^?2, a low Tafel slope of 54.9 mV dec^?1 and superior catalytic stability for OER, which is comparable to that of commercial RuO₂. Density functional theory calculations indicate N‐doping could promote catalytic activity via improving electronic conductivity, accelerating reaction kinetics, and optimizing the adsorption energy for intermediates of OER. Interestingly, N‐Co₃O₄@NC also shows a superior oxygen reduction reaction activity, making it a bifunctional electrocatalyst for zinc–air batteries. The zinc–air battery with the N‐Co₃O₄@NC cathode demonstrates superior efficiency and durability, showing the feasibility of N‐Co₃O₄/NC in electrochemical energy devices.     

Ru–Ru2PΦNPC and NPC@RuO2 Synthesized via Environment‐Friendly and Solid‐Phase Phosphating Process by Saccharomycetes as N/P Sources and Carbon Template for Overall Water Splitting in Acid Electrolyte

Although numerous ruthenium‐based phosphates possess high catalytic activities for hydrogen evolution reaction (HER), most of them rely on dangerous and toxic synthesis routes. Biological slices confirm that Ru ions can penetrate the cell walls of saccharomycete, which facilitates the adsorption of Ru ions. Herein, based on a green synthesis process by saccharomycete cells as the carbon template and nitrogen/phosphorus (N/P) sources, novel Janus‐like ruthenium–ruthenium phosphide nanoparticles embedded into a N/P dual‐doped carbon matrix (Ru–Ru₂PΦNPC) electrocatalyst for HER are synthesized. Electrochemical tests reveal that Ru–Ru₂PΦNPC displays remarkable performance with a low overpotential of 42 mV at 10 mA cm^?2 and demonstrates superior stability at a high current density in 0.5 m H₂SO₄. Furthermore, ruthenium oxide nanoparticles coated N/P dual‐doped carbon (NPC@RuO₂) are also synthesized with a yolk–shell structure using saccharomycete cells as the core template and RuO₂ as a shell to isolate saccharomycete cells from the oxidation reaction during calcination in air. The NPC@RuO₂ as oxygen evolution reaction electrocatalyst possesses a low overpotential of 220 mV at 10 mA cm^?2. Finally, the Ru–Ru₂PΦNPC is integrated as a cathode and NPC@RuO₂ is integrated as an anode to construct a two‐electrode electrolyzer to enable an excellent performance for overall water splitting with a cell voltage of 1.50 V at 10 mA cm^?2 in 0.5 m H₂SO₄.     

Atomically Thin Defect‐Rich Fe–Mn–O Hybrid Nanosheets as High Efficient Electrocatalyst for Water Oxidation

Engineering non‐noble metal–based electrocatalysts with superior water oxidation performance is highly desirable for the production of renewable chemical fuels. Here, an atomically thin low‐crystallinity Fe–Mn–O hybrid nanosheet grown on carbon cloth (Fe–Mn–O NS/CC) is successfully synthetized as an efficient oxygen evolution reaction (OER) catalyst. The synthesis strategy involves a facile reflux reaction and subsequent low‐temperature calcination process, and the morphology and composition of hybrid nanosheets can be tailored conveniently. The defect‐rich Fe–Mn–O ultrathin nanosheet with uniform element distribution enables exposure of more catalytic active sites; moreover, the atomic‐scale synergistic action of Mn and Fe oxide contributes to an enhanced intrinsic catalytic activity. Therefore, the optimized Fe–Mn–O hybrid nanosheets, with lateral sizes of about 100–600 nm and ≈1.4 nm in thickness, enable a low onset potential of 1.46 V, low overpotential of 273 mV for current density of 10 mA cm^?2, a small Tafel slope of 63.9 mV dec^?1, and superior durability, which are superior to that of individual MnO₂ and FeOOH electrode, and even outperforming most reported MnO₂‐based electrocatalysts.     

Bifunctional Heterostructure Assembly of NiFe LDH Nanosheets on NiCoP Nanowires for Highly Efficient and Stable Overall Water Splitting

3D hierarchical heterostructure NiFe LDH@NiCoP/NF electrodes are prepared successfully on nickel foam with special interface engineering and synergistic effects. This research finds that the as‐prepared NiFe LDH@NiCoP/NF electrodes have a more sophisticated inner structure and intensive interface than a simple physical mixture. The NiFe LDH@NiCoP/NF electrodes require an overpotential as low as 120 and 220 mV to deliver 10 mA cm^?2 for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1 m KOH, respectively. Tafel and electrochemical impedance spectroscopy further reveal a favorable kinetic during electrolysis. Specifically, the NiFe LDH@NiCoP/NF electrodes are simultaneously used as cathode and anode for overall water splitting, which requires a cell voltage of 1.57 V at 10 mA cm^?2. Furthermore, the synergistic effect of the heterostructure improves the structural stability and promotes the generation of active phases during HER and OER, resulting in excellent stability over 100 h of continuous operation. Moreover, the strategy and interface engineering of the introduced heterostructure can also be used to prepare other bifunctional and cost‐efficient electrocatalysts for various applications.