Graphene Decorated with Uniform Ultrathin (CoP)x–(FeP)1–x Nanorods: A Robust Non‐Noble‐Metal Catalyst for Hydrogen Evolution

Developing high‐performance but low‐cost hydrogen evolution reaction (HER) electrocatalysts with superior activity and stability for future sustainable energy conversion technologies is highly desired. Tuning of microstructure, configuration, and chemical composition are paramount to developing effective non‐noble electrocatalysts for HER. Herein, a universal “nanocasting” method is reported to construct graphene decorated with uniform ternary (CoP)_x –(FeP)_1?x (0 ≤ x ≤ 1) nanorods hybrids with different chemical compositions [(CoP)_x –(FeP)_1?x –NRs/G] as a highly active and durable nonprecious‐metal electrocatalyst for the HER. The optimized (CoP)_0.54–(FeP)_0.46–NRs/G electrocatalyst exhibits overpotentials of as low as 57 and 97 mV at 10 mA cm^?2, Tafel slopes of 52 and 62 mV dec^?1, exchange current densities of 0.489 and 0.454 mA cm^?2, and Faradaic efficiency of nearly 100% in acidic and alkaline media, respectively. More importantly, this electrocatalyst also exhibits high tolerance and durability in a wide pH range and keeps catalytic activity for at least 3000 cycles and 24 h of sustained hydrogen production. The excellent catalytic performance of the (CoP)_x –(FeP)_1?x –NRs/G electrocatalyst may be ascribed to its unique mesoporous structure and strong synergistic effect between CoP and FeP. Thus, the work provides a feasible way to fabricate cheap and highly efficient electrocatalyst as alternatives for Pt‐based electrocatalysts for HER in electrochemical water splitting.     

Coupling PtNi Ultrathin Nanowires with MXenes for Boosting Electrocatalytic Hydrogen Evolution in Both Acidic and Alkaline Solutions

Developing an efficient electrocatalyst for the hydrogen evolution reaction (HER) working in both acidic and alkaline solutions is highly desirable, but still remains challenging. Here, Pt_xNi ultrathin nanowires (NWs) with tunable compositions (x = 1.42, 3.21, 5.67) are in situ grown on MXenes (Ti₃C₂ nanosheets), serving as electrocatalysts toward HER. Such Pt_xNi@Ti₃C₂ electrocatalysts exhibit excellent HER performance in both acidic and alkaline solutions, with the Pt_3.21Ni@Ti₃C₂ being the best one. Specifically, Pt_3.21Ni@Ti₃C₂ achieves record‐breaking performance in terms of lowest overpotential (18.55 mV) and smallest Tafel slope (13.37 mV dec^?1) for HER in acidic media to date. Theory calculations and X‐ray photoelectron spectroscopy analyses demonstrate that the coupling of MXenes with the NWs not only approaches the Gibbs free energy for hydrogen adsorption close to zero through the electron transfer between them in acidic media, but also provides additional active sites for water dissociation in alkaline solution, both of them being beneficial to the HER performance.     

Hierarchically Porous W‐Doped CoP Nanoflake Arrays as Highly Efficient and Stable Electrocatalyst for pH‐Universal Hydrogen Evolution

It is still challenging to develop high‐efficiency and low‐cost non‐noble metal‐based electrocatalysts for hydrogen evolution reaction (HER) in pH‐universal electrolytes. Herein, hierarchically porous W‐doped CoP nanoflake arrays on carbon cloth (W‐CoP NAs/CC) are synthesized via facile liquid‐phase reactions and a subsequent phosphorization process. The W‐CoP NAs/CC hybrid can be directly employed as a binder‐free electrocatalyst and delivers superior HER performance in pH‐universal electrolytes. Especially, it delivers very low overpotentials of 89, 94, and 102 mV to reach a current density of 10 mA cm^–2 in acidic, alkaline, and neutral electrolytes, respectively. Furthermore, it shows a nearly 100% Faradaic efficiency as well as superior long‐term stability with no decreasing up to 36 h in pH‐universal electrolytes. The outstanding electrocatalytic performance of W‐CoP NAs/CC can be mainly attributed to the porous W‐doped nanoflake arrays, which not only afford rich exposed active sites, but also accelerate the access of electrolytes and the diffusion of H₂ bubbles, thus efficiently promoting the HER performance. This work provides a new horizon to rationally design and synthesize highly effective and stable non‐noble metal phosphide‐based pH‐universal electrocatalysts for HER.     

Fabrication of Hollow CoP/TiOx Heterostructures for Enhanced Oxygen Evolution Reaction

Transition‐metal phosphides have flourished as promising candidates for oxygen evolution reaction (OER) electrocatalysts. Herein, it is demonstrated that the electrocatalytic OER performance of CoP can be greatly improved by constructing a hybrid CoP/TiO_x heterostructure. The CoP/TiO_x heterostructure is fabricated using metal–organic framework nanocrystals as templates, which leads to unique hollow structures and uniformly distributed CoP nanoparticles on TiO_x. The strong interactions between CoP and TiO_x in the CoP/TiO_x heterostructure and the conductive nature of TiO_x with Ti³⁺ sites endow the CoP–TiO_x hybrid material with high OER activity comparable to the state‐of‐the‐art IrO₂ or RuO₂ OER electrocatalysts. In combination with theoretical calculations, this work reveals that the formation of CoP/TiO_x heterostructure can generate a pathway for facile electron transport and optimize the water adsorption energy, thus promoting the OER electrocatalysis.     

Defect‐Induced Pt–Co–Se Coordinated Sites with Highly Asymmetrical Electronic Distribution for Boosting Oxygen‐Involving Electrocatalysis

Rational design and synthesis of hetero‐coordinated moieties at the atomic scale can significantly raise the performance of the catalyst and obtain mechanistic insight into the oxygen‐involving electrocatalysis. Here, a facile plasma‐photochemical strategy is applied to construct atomically coordinated Pt–Co–Se moieties in defective CoSe₂ (CoSe_2?x) through filling the plasma‐created Se vacancies in CoSe_2?x with single Pt atomic species (CoSe_2?x‐Pt) under ultraviolet irradiation. The filling of single Pt can remarkably enhance the oxygen evolution reaction (OER) activity of CoSe₂. Optimal OER specific activity is achieved with a Pt content of 2.25 wt% in CoSe_2?x‐Pt, exceeding that of CoSe_2?x by a factor of 9. CoSe_2?x‐Pt shows much better OER performance than CoSe_2?x filled with single Ni and even Ru atomic species (CoSe_2?x‐Ni and CoSe_2?x‐Ru). Noticeably, it is general that Pt is not a good OER catalyst but Ru is; thus the design of active sites for electrocatalysis at an atomic level should follow a different intrinsic mechanism. Mechanism studies unravel that the single Pt can induce much higher electronic distribution asymmetry degree than both single Ni and Ru, and benefit the interaction between the Co sites and adsorbates (OH*, O*, and OOH*) during the OER process, leading to a better OER activity.     

Highly Robust Non‐Noble Alkaline Hydrogen‐Evolving Electrocatalyst from Se‐Doped Molybdenum Disulfide Particles on Interwoven CoSe2 Nanowire Arrays

Developing efficient non‐noble and earth‐abundant hydrogen‐evolving electrocatalysts is highly desirable for improving the energy efficiency of water splitting in base. Molybdenum disulfide (MoS₂) is a promising candidate, but its catalytic activity is kinetically retarded in alkaline media due to the unfavorable water adsorption and dissociation feature. A heterogeneous electrocatalyst is reported that is constructed by selenium‐doped MoS₂ (Se‐MoS₂) particles on 3D interwoven cobalt diselenide (CoSe₂) nanowire arrays that drives the hydrogen evolution reaction (HER) with fast reaction kinetics in base. The resultant Se‐MoS₂/CoSe₂ hybrid exhibits an outstanding catalytic HER performance with extremely low overpotentials of 30 and 93 mV at 10 and 100 mA cm^–2 in base, respectively, which outperforms most of the inexpensive alkaline HER catalysts, and is among the best alkaline catalytic activity reported so far. Moreover, this hybrid catalyst shows exceptional catalytic performance with very low overpotentials of 84 and 95 mV at 10 mA cm^–2 in acidic and neutral electrolytes, respectively, implying robust pH universality of this hybrid catalyst. This work may provide new inspirations for the development of high‐performance MoS₂‐based HER electrocatalysts in unfavorable basic media for promising catalytic applications.     

Cactus‐Like Hollow Cu2‐xS@Ru Nanoplates as Excellent and Robust Electrocatalysts for the Alkaline Hydrogen Evolution Reaction

The development of Pt‐free electrocatalysts for the hydrogen evolution reaction (HER) recently is a focus of great interest. While several strategies are developed to control the structural properties of non‐Pt catalysts and boost their electrocatalytic activities for the HER, the generation of highly reactive defects or interfaces by combining a metal with other metals, or with metal oxides/sulfides, can lead to notably enhanced catalytic performance. Herein, the preparation of cactus‐like hollow Cu_2‐x S@Ru nanoplates (NPs) that contain metal/metal sulfide heterojunctions and show excellent catalytic activity and durability for the HER in alkaline media is reported. The initial formation of Ru islands on presynthesized Cu_1.94S NPs, via cation exchange between three Cu⁺ ions and one Ru³⁺, induces the growth of the Ru phase, which is concomitant with the dissolution of the Cu_1.94S nanotemplate, culminating in the formation of a hollow nanostructure with numerous thin Ru pillars. Hollow Cu_2‐x S@Ru NPs exhibit a small overpotential of 82 mV at a current density of ?10 mA cm^?2 and a low Tafel slope of 48 mV dec^?1 under alkaline conditions; this catalyst is among state‐of‐the‐art HER electrocatalysts in alkaline media. The excellent performance of hollow Cu_2‐x S@Ru NPs originates from the facile dissociation of water in the Volmer step.     

Colloidal Cobalt Phosphide Nanocrystals as Trifunctional Electrocatalysts for Overall Water Splitting Powered by a Zinc–Air Battery

Highly efficient and stable electrocatalysts, particularly those that are capable of multifunctionality in the same electrolyte, are in high demand for the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR). In this work, highly monodisperse CoP and Co₂P nanocrystals (NCs) are synthesized using a robust solution‐phase method. The highly exposed (211) crystal plane and abundant surface phosphide atoms make the CoP NCs efficient catalysts toward ORR and HER, while metal‐rich Co₂P NCs show higher OER performance owing to easier formation of plentiful Co₂P@COOH heterojunctions. Density functional theory calculation results indicate that the desorption of OH* from cobalt sites is the rate‐limiting step for both CoP and Co₂P in ORR and that the high content of phosphide can lower the reaction barrier. A water electrolyzer constructed with a CoP NC cathode and a Co₂P NC anode can achieve a current density of 10 mA cm^?2 at 1.56 V, comparable even to the noble metal‐based Pt/C and RuO₂/C pair. Furthermore, the CoP NCs are employed as an air cathode in a primary zinc–air battery, exhibiting a high power density of 62 mW cm^?2 and good stability.     

Biomorphic Co?N?C/CoOx Composite Derived from Natural Chloroplasts as Efficient Electrocatalyst for Oxygen Reduction Reaction

Natural chloroplasts containing big amounts of chlorophylls (magnesium porphyrin, Mg‐Chl) are employed both as template and porphyrin source to synthesize biomorphic Co? N? C/CoO_x composite as electrocatalyst for the oxygen reduction reaction (ORR). Cobalt‐substituted chlorophyll derivative (Co‐Chl) in chloroplasts is first obtained by successively rinsing in hydrochloric acid and cobalt acetate solutions. After calcining in nitrogen to 800 °C, Co‐Chl is transferred to Co? N? C; while other parts of chloroplasts adsorbed with Co ions are transferred to CoO_x retaining the microarchitecture of chloroplasts. The abundant active Co? N? C sites are protected by circumjacent biocarbon and CoO_x to avoid leakage and agglomeration, and at the same time can overcome the poor conductivity weakness of CoO_x by directly transporting electrons to the carbonaceous skeleton. This unique synergistic effect, together with efficient bioarchitecture, leads to good electrocatalytical performance for the ORR. The onset and half‐wave potentials are 0.89 and 0.82 V versus reversible hydrogen electrode, respectively, with better durability and methanol tolerance than that of commercial Pt/C. Different from the traditional concept of biomorphic materials which simply utilize bioarchitectures, this work provides a new example of coupling bioderivative components with bioarchitectures into one integrated system to achieve good comprehensive performance for electrocatalysts.     

Nickel Diselenide Ultrathin Nanowires Decorated with Amorphous Nickel Oxide Nanoparticles for Enhanced Water Splitting Electrocatalysis

Well‐designed hybrid materials based on noble metal‐free elements have great potential to generate hydrogen (H₂) and oxygen (O₂) sustainably via overall water splitting for developing practical energy‐related technologies. Herein, an accessible method is presented to synthesize nickel diselenide (NiSe₂) ultrathin nanowires decorated with amorphous nickel oxide nanoparticles (NiO_x NPs) as multifunctional electrocatalysts (NSWANs) for hydrogen and oxygen evolution reaction (HER and OER). The NSWANs exhibit quite low HER and OER overpotentials of 174 and 295 mV, respectively, holding the current density of 20 mA cm^?2 for 24 h continuous operations in alkaline media. Meanwhile, a cell voltage of 1.547 V at the current density of 10 mA cm^?2 for overall water splitting has been achieved by the NSWANs for the practical application, which could maintain fascinating activity of 20 mA cm^?2 for 72 h without degradation. The decorated NiO_x NPs not only prevent the NiSe₂ from further oxidation but also expose requisite active sites for electrocatalytic process. It is believed that this study may provide a valuable strategy to design high‐efficiency electrocatalysts and expand the applications of selenide‐based materials.     

Regulating Water‐Reduction Kinetics in Cobalt Phosphide for Enhancing HER Catalytic Activity in Alkaline Solution

Electrochemical water splitting to produce hydrogen renders a promising pathway for renewable energy storage. Considering limited electrocatalysts have good oxygen‐evolution reaction (OER) catalytic activity in acid solution while numerous economical materials show excellent OER catalytic performance in alkaline solution, developing new strategies that enhance the alkaline hydrogen‐evolution reaction (HER) catalytic activity of cost‐effective catalysts is highly desirable for achieving highly efficient overall water splitting. Herein, it is demonstrated that synergistic regulation of water dissociation and optimization of hydrogen adsorption free energy on electrocatalysts can significantly promote alkaline HER catalysis. Using oxygen‐incorporated Co₂P as an example, the synergistic effect brings about 15‐fold enhancement of alkaline HER activity. Theory calculations confirm that the water dissociation free energy of Co₂P decreases significantly after oxygen incorporation, and the hydrogen adsorption free energy can also be optimized simultaneously. The finding suggests the powerful effectiveness of synergetic regulation of water dissociation and optimization of hydrogen adsorption free energy on electrocatalysts for alkaline HER catalysis.     

Reduced graphene oxide/CoSe2 nanocomposites: hydrothermal synthesis and their enhanced electrocatalytic activity

Reduced graphene oxide (RGO)/CoSe₂ nanocomposites were synthesized by self-assembly of CoSe₂/DETA (DETA: diethylenetriamine) onto the surface of graphene oxide (GO), followed by subsequent chemical reduction of GO during a hydrothermal process. The as-synthesized products were characterized by powder X-ray diffraction, energy dispersive X-ray spectroscopy, Raman spectra, scanning electron microscopy, and transmission electron microscopy. The morphology of the CoSe₂ on the RGO nanosheets can be well controlled by adjusting the reaction time during the hydrothermal process. The catalytic activities of the RGO/CoSe₂ nanocomposites were investigated for oxygen evolution reaction (OER) in alkaline conditions. It was found that the as-formed RGO/CoSe₂ nanocomposites show higher catalytic activity compared with the unsupported CoSe₂. In addition, the loading amounts and morphologies of CoSe₂ on RGO sheets have a great influence on the catalytic performance of RGO/CoSe₂. Our studies raise promising possibilities for designing effective OER electrocatalysts for energy conversion.     

Nickel–Cobalt Diselenide 3D Mesoporous Nanosheet Networks Supported on Ni Foam: An All‐pH Highly Efficient Integrated Electrocatalyst for Hydrogen Evolution

Novel 3D Ni_1?x Co_x Se₂ mesoporous nanosheet networks with tunable stoichiometry are successfully synthesized on Ni foam (Ni_1?x Co_x Se₂ MNSN/NF with x ranging from 0 to 0.35). The collective effects of special morphological design and electronic structure engineering enable the integrated electrocatalyst to have very high activity for hydrogen evolution reaction (HER) and excellent stability in a wide pH range. Ni_0.89Co_0.11Se₂ MNSN/NF is revealed to exhibit an overpotential (η₁₀) of 85 mV at ?10 mA cm^?2 in alkaline medium (pH 14) and η₁₀ of 52 mV in acidic solution (pH 0), which are the best among all selenide‐based electrocatalysts reported thus far. In particular, it is shown for the first time that the catalyst can work efficiently in neutral solution (pH 7) with a record η₁₀ of 82 mV for all noble metal‐free electrocatalysts ever reported. Based on theoretical calculations, it is further verified that the advanced all‐pH HER activity of Ni_0.89Co_0.11Se₂ is originated from the enhanced adsorption of both H⁺ and H₂O induced by the substitutional doping of cobalt at an optimal level. It is believed that the present work provides a valuable route for the design and synthesis of inexpensive and efficient all‐pH HER electrocatalysts.     

Synergistic Coupling of Ni Nanoparticles with Ni3C Nanosheets for Highly Efficient Overall Water Splitting

Exploring earth‐abundant bifunctional electrocatalysts with high efficiency for water electrolysis is extremely demanding and challenging. Herein, density functional theory (DFT) predictions reveal that coupling Ni with Ni₃C can not only facilitate the oxygen evolution reaction (OER) kinetics, but also optimize the hydrogen adsorption and water adsorption energies. Experimentally, a facile strategy is designed to in situ fabricate Ni₃C nanosheets on carbon cloth (CC), and simultaneously couple with Ni nanoparticles, resulting in the formation of an integrated heterostructure catalyst (Ni–Ni₃C/CC). Benefiting from the superior intrinsic activity as well as the abundant active sites, the Ni–Ni₃C/CC electrode demonstrates excellent bifunctional electrocatalytic activities toward the OER and hydrogen evolution reaction (HER), which are superior to all the documented Ni₃C‐based electrocatalysts in alkaline electrolytes. Specifically, the Ni–Ni₃C/CC catalyst exhibits the low overpotentials of only 299 mV at the current density of 20 mA cm^?2 for the OER and 98 mV at 10 mA cm^?2 for the HER in 1 m KOH. Furthermore, the bifunctional Ni–Ni₃C/CC catalyst can propel water electrolysis with excellent activity and nearly 100% faradic efficiency. This work highlights an easy approach for designing and constructing advanced nickel carbide‐based catalysts with high activity based on the theoretical predictions.     

Nitrogen Engineering on 3D Dandelion‐Flower‐Like CoS2 for High‐Performance Overall Water Splitting

Searching for highly efficient and stable bifunctional electrocatalysts toward hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is highly desirable for the practical application of water electrolysis under alkaline electrolyte. Although electrocatalysts based on transition metal sulfides (TMSs) are widely studied as efficient (pre)catalysts toward OER under alkaline media, their HER performances are far less than the state‐of‐the‐art Pt catalyst. Herein, the synthesis of nitrogen doped 3D dandelion‐flower‐like CoS₂ architecture directly grown on Ni foam (N‐CoS₂/NF) is reported that possesses outstanding HER activity and durability, with an overpotential of 28 mV to obtain the current density of 10 mA cm^?2, exceeding almost all the documented TMS‐based electrocatalysts. Density functional theory calculations and experimental results reveal that the d‐band center of CoS₂ could be efficiently tailored by N doping, resulting in optimized adsorption free energies of hydrogen (ΔG_*H) and water , which can accelerate the HER process in alkaline electrolyte. Besides, the resulting N‐CoS₂/NF also displays excellent performance for OER, making it a high‐performance bifunctional electrocatalyst toward overall water splitting, with a cell voltage of 1.50 V to achieve 10 mA cm^?2.     

Optimizing the Electronic Structure of Atomically Dispersed Ru Sites with CoP for Highly Efficient Hydrogen Evolution in both Alkaline and Acidic Media

Developing efficient and stable electrocatalysts for hydrogen evolution reaction (HER) over a wide pH range and industrial large-scale hydrogen production is critical and challenging. Here, a tailoring strategy is developed to fabricate an outstanding HER catalyst in both acidic and alkaline electrolytes containing high-density atomically dispersed Ru sites anchored in the CoP nanoparticles supported on carbon spheres (NC@Ru_SA-CoP). The obtained NC@Ru_SA-CoP catalyst exhibits excellent HER performance with overpotentials of only 15 and 13 mV at 10 mA cm⁻² in 1 m KOH and 0.5 m H₂SO₄, respectively. The experimental results and theoretical calculations indicate that the strong interaction between the Ru site and the CoP can effectively optimize the electronic structure of Ru sites to reduce the hydrogen binding energy and the water dissociation energy barrier. The constructed alkaline anion exchange membrane water electrolyze (AAEMWE) demonstrates remarkable durability and an industrial-level current density of 1560 mA cm⁻² at 1.8 V. This strategy provides a new perspective on the design of Ru-based electrocatalysts with suitable intermediate adsorption strengths and paves the way for the development of highly active electrocatalysts for industrial-scale hydrogen production.     

2D Cobalt Chalcogenide Heteronanostructures Enable Efficient Alkaline Hydrogen Evolution Reaction

The development of high-efficiency non-precious metal electrocatalysts for alkaline electrolyte hydrogen evolution reactions (HER) is of great significance in energy conversion to overcome the limited supply of fossil fuels and carbon emission. Here, a highly active electrocatalyst is presented for hydrogen production, consisting of 2D CoSe₂/Co₃S₄ heterostructured nanosheets along Co₃O₄ nanofibers. The different reaction rate between the ion exchange reaction and redox reaction leads to the heterogeneous volume swelling, promoting the growth of 2D structure. The 2D/1D heteronanostructures enable the improved the electrochemical active area, the number of active sites, and more favorable H binding energy compared to individual cobalt chalcogenides. The roles of the different composition of the heterojunction are investigated, and the electrocatalysts based on the CoSe₂/Co₃S₄@Co₃O₄ exhibited an overpotential as low as 165 mV for 10 mA cm⁻² and 393 mV for 200 mA cm⁻² in 1 m KOH electrolyte. The as-prepared electrocatalysts remained active after 55 h operation without any significant decrease, indicating the excellent long-term operation stability of the electrode. The Faradaic efficiency of hydrogen production is close to 100% at different voltages. This work provides a new design strategy toward Co-based catalysts for efficient alkaline HER.     

High-Performance Bifunctional Porous Iron-Rich Phosphide/Nickel Nitride Heterostructures for Alkaline Seawater Splitting

Seawater is the most abundant natural water resource in the world, which is an inexhaustible and low-cost feedstock for hydrogen production by alkaline water electrolysis. It is appearling to develop robust and stable electrocatalysts for alkaline seawater electrolysis. However, the development of seawater electrolysis is seriously impeded by anodic chloride corrosion and chlorine evolution reaction, and few non-noble electrocatalysts show prominent catalytic performance and excellent durability. Here, a heterogeneous electrocatalyst constructed by in situ growing highly dispersed iron-rich bimetallic phosphide nanoparticles on metallic Ni₃N (Fe_2−2xCo_2xP/Ni₃N), which exhibits outstanding bifunctional catalytic activities for alkaline seawater splitting, is reported. The optimal (Fe_0.74Co_0.26)₂P/Ni₃N and Fe₂P/Ni₃N electrocatalysts demand only 113 and 212 mV to afford 100 mA cm⁻² for hydrogen and oxygen evolution reactions (HER and OER) in 1 m KOH, respectively, thus substantially expediting overall water/seawater electrolysis at 100 mA cm⁻² with 1.592/1.645 V. Particularly, Fe₂P/Ni₃N displays an unprecedented overpotential of 302 mV at 500 mA cm⁻², which represents the best alkaline seawater oxygen evolution activity among the ever-reported non-noble electrocatalysts; and thus substantially expedites overall water/seawater splitting at 500 mA cm⁻² with 1.701/1.768 V, surpassing most of the reported non-noble lectrocatalysts. This work provides a new approach for developing high-performance electrocatalysts for seawater splitting.     

Synergism of Geometric Construction and Electronic Regulation: 3D Se‐(NiCo)Sx/(OH)x Nanosheets for Highly Efficient Overall Water Splitting

The exploration of highly efficient electrocatalysts for both oxygen and hydrogen generation via water splitting is receiving considerable attention in recent decades. Up till now, Pt‐based catalysts still exhibit the best hydrogen evolution reaction (HER) performance and Ir/Ru‐based oxides are identified as the benchmark for oxygen evolution reaction (OER). However, the high cost and rarity of these materials extremely hinder their large‐scale applications. This paper describes the construction of the ultrathin defect‐enriched 3D Se‐(NiCo)S_x/(OH)_x nanosheets for overall water splitting through a facile Se‐induced hydrothermal treatment. Via Se‐induced fabrication, highly efficient Se‐(NiCo)S_x/(OH)_x nanosheets are successfully fabricated through morphology optimization, defect engineering, and electronic structure tailoring. The as‐prepared hybrids exhibit relatively low overpotentials of 155 and 103 mV at the current density of 10 mA cm^?2 for OER and HER, respectively. Moreover, an overall water‐splitting device delivers a current density of 10 mA cm^?2 for ≈66 h without obvious degradation.     

Ultrathin Cobalt Oxide Layers as Electrocatalysts for High‐Performance Flexible Zn–Air Batteries

Synergistic improvements in the electrical conductivity and catalytic activity for the oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) are of paramount importance for rechargeable metal–air batteries. In this study, one‐nanometer‐scale ultrathin cobalt oxide (CoO_x) layers are fabricated on a conducting substrate (i.e., a metallic Co/N‐doped graphene substrate) to achieve superior bifunctional activity in both the ORR and OER and ultrahigh output power for flexible Zn–air batteries. Specifically, at the atomic scale, the ultrathin CoO_x layers effectively accelerate electron conduction and provide abundant active sites. X‐ray absorption spectroscopy reveals that the metallic Co/N‐doped graphene substrate contributes to electron transfer toward the ultrathin CoO_x layer, which is beneficial for the electrocatalytic process. The as‐obtained electrocatalyst exhibits ultrahigh electrochemical activity with a positive half‐wave potential of 0.896 V for ORR and a low overpotential of 370 mV at 10 mA cm^?2 for OER. The flexible Zn–air battery built with this catalyst exhibits an ultrahigh specific power of 300 W g_cat ^?1, which is essential for portable devices. This work provides a new design pathway for electrocatalysts for high‐performance rechargeable metal–air battery systems.