Unraveling the Synergistic Mechanism of Bi-Functional Nickel–Iron Phosphides Catalysts for Overall Water Splitting

Ni–Fe bimetallic electrocatalysts are expected to replace existing precious metal catalysts for water splitting and achieve industrial applications due to their high intrinsic activity and low cost. However, the mechanism by which Ni and Fe species synergistically enhance catalytic activity remains obscure, which still needs further in-depth study. In this study, a highly active bi-functional electrocatalyst of Ni₂P/FeP heterostructures is constructed on Fe foam (Ni₂P/FeP-FF), clearly illustrating the effect of Ni on Fe species for oxygen evolution reaction (OER) and revealing the true catalytic active phase for hydrogen evolution reaction (HER). The Ni₂P/FeP-FF only needs overpotentials of 217 and 42 mV to reach 10 mA cm⁻² for OER and HER, respectively, exhibiting superior bi-functional activity for overall water splitting. The Ni can elevate the strength of Fe O on Ni₂P/FeP-FF surface and promote the formation of high-valence FeOOH phase during OER, thus enhancing OER performance. Based on first-principles calculations and Raman characterizations, the Ni₂P/Ni(OH)₂ heterojunction evolved from Ni₂P/FeP is identified as the real high active phase for HER. This study not only builds a near-commercial bifunctional electrocatalyst for overall water splitting, but also provides a deep insight for synergistic catalytic mechanism of Ni and Fe species.     

Mechanochemical Post-Synthesis of Metal–Organic Framework-Based Pre-Electrocatalysts with Surface Fe?O?Ni/Co Bonding for Highly Efficient Oxygen Evolution

Rational surface engineering of metal–organic frameworks (MOFs) provide potential opportunities to address the sluggish kinetics of oxygen evolution reaction (OER). However, the development of MOF-based materials with low overpotentials remains a great challenge. Herein, a post-synthesis strategy to prepare highly efficient MOF-based pre-electrocatalysts via all-solid-phase mechanochemistry is demonstrated. The surface of a Fe-based MOF (MIL-53) can be reconstructed and anchored with atomically dispersed Ni/Co sites. As expected, the optimized M-NiA-CoN exhibits a very low overpotential of 180 mV at 10 mA cm⁻² and a small Tafel slope of 41 mV dec⁻¹ in 1 m KOH electrolyte. The superior electrocatalytic OER activity is mainly due to the formation of surface Fe O Ni/Co bonding. Furthermore, density functional theory calculations reveal that the transformation from ^*OH to ^*O is the rate-determining step and the electrocatalytic OER activity trend at different metal sites is Co > Ni≈Fe.     

Dual-Sites Coordination Engineering of Single Atom Catalysts for Full-Temperature Adaptive Flexible Ultralong-Life Solid-State Zn−Air Batteries

High-performance rechargeable Zn-air batteries with long-life stability are desirable for power applications in electric vehicles. The key component of the Zn-air batteries is the bifunctional oxygen electrocatalyst, however, designing a bifunctional oxygen electrocatalyst with high intrinsic reversibility and durability is a challenge. Through density functional theory calculations, it is found that the catalytic activity originated from the electronic and geometric coordination structures synergistic effect of the Fe and Co dual-sites with metal-N₄ coordination environment, assisting the stronger hybridization of electronic orbitals between Co (dxz, dz²) and OO* (px, pz), thus making the stronger O₂ active ability of Co active site. These findings enable to development of a fancy dual single-atom catalyst comprising adjacent Fe N₄ and Co N₄ sites on N-doped carbon matrix (FeCo-NC). FeCo-NC exhibits extraordinary bifunctional activities for oxygen reduction and evolution reaction (ORR/OER), which displays high half-wave potential (0.893 V) for the ORR, and low overpotential (343 mV) at 10 mA cm⁻² for the OER. The assembled FeCo-NC air-electrode works well in the flexible solid-state Zn-air battery with a high specific capacity of 747.0 mAh g⁻¹, a long-time stability of more than 400 h (30 °C), and also a superior performance at extreme temperatures (−30 °C–60 °C).     

Catalyst-Support Interactions in Zr2ON2-Supported IrOx Electrocatalysts to Break the Trade-Off Relationship Between the Activity and Stability in the Acidic Oxygen Evolution Reaction

The development of highly active and durable Ir-based electrocatalysts for the acidic oxygen evolution reaction (OER) is challenging because of the corrosive anodic conditions. Herein, IrO_x/Zr₂ON₂ electrocatalyst is demonstrated, employing Zr₂ON₂ as a support material, to overcome the trade-off between the activity and stability in the OER. Zr₂ON₂ is selected due to its excellent electrical conductivity and chemical stability, and the fact that it induces strong interactions with IrO_x catalysts. As a result, IrO_x/Zr₂ON₂ electrocatalysts exhibit outstanding OER performances, reaching an overpotential of 255 mV at 10 mA cm⁻² and a mass activity of 849 mA mg_Ir⁻¹ at 1.55 V (vs the reversible hydrogen electrode). The activity of IrO_x/Zr₂ON₂ is maintained at 10 mA cm⁻² for 5 h, while in contrast, IrO_x/ZrN and an unsupported IrO_x catalyst undergo drastic degradation. Combined experimental X-ray analyses and theoretical interpretations reveal that the reduced oxidation state of Ir and the extended Ir O bond distance in IrO_x/Zr₂ON₂ effectively increase the activity and stability of IrO_x by altering reaction pathway from a conventional adsorbate evolution mechanism to a lattice oxygen-participating mechanism. These results demonstrate that it is possible to effectively reduce the Ir content in OER catalysts through interface engineering without sacrificing the catalytic performance.     

Fe?N4O?C Nanoplates Covalently Bonding on Graphene for Efficient CO2 Electroreduction and Zn?CO2 Batteries (Adv. Funct. Mater. 27/2023)

Electrochemical carbon dioxide (CO₂) reduction into value-added products holds great promise in moving toward carbon neutrality but remains a grand challenge due to lack of efficient electrocatalysts. Herein, the nucleophilic substitution reaction is elaborately harnessed to synthesize carbon nanoplates with a Fe N₄O configuration anchored onto graphene substrate (Fe N₄O C/Gr) through covalent linkages. Density functional theory calculations demonstrate the unique configuration of Fe N₄O with one oxygen (O) atom in the axial direction not only suppresses the competing hydrogen evolution reaction, but also facilitates the desorption of *CO intermediate compared with the commonly planar single-atomic Fe sites. The Fe N₄O C/Gr shows excellent performance in the electroreduction of CO₂ into carbon monoxide (CO) with an impressive Faradaic efficiency of 98.3% at −0.7 V versus reversible hydrogen electrode (RHE) and a high turnover frequency of 3511 h⁻¹. Furthermore, as a cathode catalyst in an aqueous zinc (Zn)-CO₂ battery, the Fe N₄O C/Gr achieves a high CO Faradaic efficiency (≈91%) at a discharge current density of 3 mA cm⁻² and long-term stability over 74 h. This work opens up a new route to simultaneously modulate the geometric and electronic structure of single-atomic catalysts toward efficient CO₂ conversion.     

Coupling Adsorbed Evolution and Lattice Oxygen Mechanism in Fe-Co(OH)2/Fe2O3 Heterostructure for Enhanced Electrochemical Water Oxidation

Oxygen evolution reaction (OER) remains a bottleneck for electrocatalytic water-splitting to generate hydrogen. However, the traditional adsorbed evolution mechanism (AEM) possesses sluggish reaction kinetics due to the scaling relationship, while lattice oxygen mechanism (LOM) triggers an unstable structure due to the escaping of lattice oxygen. Herein, a proof-of-concept Fe-Co(OH)₂/Fe₂O₃ heterostructure is put forward, where Fe-Co(OH)₂ following AEM can complete rapidly deprotonation process while Fe₂O₃ following LOM can trigger O─O coupling step. Combining the theoretical and experimental investigation confirmed that the redistributed space-charge of Fe-Co(OH)₂/Fe₂O₃ junction can optimize synergistically adsorbed and lattice oxygen, the coupling mechanism of AEM and LOM can facilitate synchronously the OER activity and stability. As a result, the Fe-Co(OH)₂/Fe₂O₃ heterostructure shows excellent OER performance with low overpotential of only 219 and 249 mV to reach a current density of 10 and 100 mA cm⁻². Specifically, the Fe-Co(OH)₂/Fe₂O₃ electrocatalyst maintains excellent long-term stability for 100 h at a large current density of 100 mA cm⁻². This work paves an avenue to break through the limit of the conventional OER mechanism.     

Highly Dispersed NiO Clusters Induced Electron Delocalization of Ni?N?C Catalysts for Enhanced CO2 Electroreduction

Oxygen-regulated Ni-based single-atom catalysts (SACs) show great potential in accelerating the kinetics of electrocatalytic CO₂ reduction reaction (CO₂RR). However, it remains a challenge to precisely control the coordination environment of Ni O moieties and achieve high activity at high overpotentials. Herein, a facile carbonization coupled oxidation strategy is developed to mass produce NiO clusters-decorated Ni N C SACs that exhibit a high Faradaic efficiency of CO (maximum of 96.5%) over a wide potential range (−0.9 to −1.3 V versus reversible hydrogen electrode) and a high turnover frequency for CO production of 10 120 h⁻¹ even at the high overpotential of 1.19 V. Density functional theory calculations reveal that the highly dispersed NiO clusters induce electron delocalization of active sites and reduce the energy barriers for *COOH intermediates formation from CO₂, leading to an enhanced reaction kinetics for CO production. This study opens a new universal pathway for the construction of oxygen-regulated metal-based SACs for various catalytic applications.     

V “Bridged” Co?O to Eliminate Charge Transfer Barriers and Drive Lattice Oxygen Oxidation during Water-Splitting

Oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) play significant role on the practical applications of water splitting for producing clean fuel. Although some low-cost metal oxides are active on catalyzing OER and HER, the instinct drawback of sluggish charges carriers transfer mobility decrease the reactions kinetic and hinder their application. To overcome the issue, Co V oxide is successfully built-up with a Co O V structure to eliminate energy barrier during carriers transfer by the spin-flip hopping process, which can be coated on various substrate to stimulate OER and HER. Moreover, the V “bridge” between Co O bonds stimulates the OER through more effective lattice oxygen oxidation mechanism, which can directly format O O bond in more effective pathway. The protocol could be spread on rational design of such OER electrocatalysts on various electrode to lower-cost water splitting.     

In Situ Reconstruction of V-Doped Ni2P Pre-Catalysts with Tunable Electronic Structures for Water Oxidation

Nickel-based electrocatalysts are promising candidates for oxygen evolution reaction (OER) but suffer from high activation overpotentials. Herein, in situ structural reconstruction of V-doped Ni₂P pre-catalyst to form highly active NiV oxyhydroxides for OER is reported, during which the partial dissolution of V creates a disordered Ni structure with an enlarged electrochemical surface area. Operando electrochemical impedance spectroscopy reveals that the synergistic interaction between the Ni hosts and the remaining V dopants can regulate the electronic structure of NiV oxyhydroxides, which leads to enhanced kinetics for the adsorption of *OH and deprotonation of *OOH intermediates. Raman spectroscopy and X-ray absorption spectroscopy further demonstrate that the increased content of active β-NiOOH phase with the disordered Ni active sites contributes to OER activity enhancement. Density functional theory calculations verify that the V dopants facilitate the generation of *O intermediates during OER, which is the rate-determining step for realizing efficient O₂ evolution. Optimization of these properties endows the NiV oxyhydroxide electrode with a low overpotential of 221 mV to deliver a current density of 10 mA cm⁻² and excellent stability in the alkaline electrolyte.     

Sulfate-Functionalized RuFeOx as Highly Efficient Oxygen Evolution Reaction Electrocatalyst in Acid

The design of highly active, stable, and low-cost electrocatalysts for the oxygen evolution reaction (OER) in proton exchange membrane water electrolyzer remains a challenge. RuO₂ shows relatively low cost but poor stability. Here, the critical role of sulfate anion doping in promoting OER activity and stability of RuO₂ is reported. Coupled with the Fe cation doping, the sulfate-functionalized RuFeO_x (S-RuFeO_x) displays a remarkable OER performance with a low overpotential of 187 mV at 10 mA cm⁻² in acid, and much enhanced stability. The excellent OER activity of S-RuFeO_x is attributed to the dual positive effects that the sulfate dopants weaken the adsorption of the *OO H intermediate, and Fe dopants promote the deprotonation of chemisorbed water molecules to form *OOH. The enhanced stability is in part due to the sulfate dopants which stabilize the lattice oxygen. These results demonstrate that the anion and cation co-doped RuO₂ is a promising candidate for highly efficient OER electrocatalysts.     

Realizing the Synergy of Interface Engineering and Chemical Substitution for Ni3N Enables its Bifunctionality Toward Hydrazine Oxidation Assisted Energy-Saving Hydrogen Production

Hydrazine oxidation assisted water electrolysis offers a unique rationale for energy-saving hydrogen production, yet the lack of effective non-noble-metal bifunctional catalysts is still a grand challenge at the current stage. Here, the Mo doped Ni₃N and Ni heterostructure porous nanosheets grow on Ni foam (denoted as Mo Ni₃N/Ni/NF) are successfully constructed, featuring simultaneous interface engineering and chemical substitution, which endow the outstanding bifunctional electrocatalytic performances toward both hydrazine oxidation reaction (HzOR) and hydrogen evolution reaction (HER), demanding a working potential of −0.3 mV to reach 10 mA cm⁻² for HzOR and −45 mV for that of HER. Impressively, the overall hydrazine splitting (OHzS) system requires an ultralow cell voltage of 55 mV to deliver 10 mA cm⁻² with remarkable long-term durability. Moreover, as a proof-of-concept, economical H₂ production systems utilizing OHzS unit powered by a waste AAA battery, a commercial solar cell, and a homemade direct hydrazine fuel cell (DHzFC) are investigated to inspire future practical applications. The density functional theory calculations demonstrate that the synergy of Mo substitution and abundant Ni₃N/Ni interface owns a more thermoneutral value for H* absorption ability toward HER and optimized dehydrogenation process for HzOR.     

Metal‐Ion (Fe,V, Co,and Ni)‐Doped MnO2 Ultrathin Nanosheets Supported on Carbon Fiber Paper for the Oxygen Evolution Reaction

Manganese dioxides (MnO₂) are considered one of the most attractive materials as an oxygen evolution reaction (OER) electrode due to its low cost, natural abundance, easy synthesis, and environmental friendliness. Here, metal‐ion (Fe, V, Co, and Ni)‐doped MnO₂ ultrathin nanosheets electrodeposited on carbon fiber paper (CFP) are fabricated using a facile anodic co‐electrodeposition method. A high density of nanoclusters is observed on the surface of the carbon fibers consisting of doped MnO₂ ultrathin nanosheets with an approximate thickness of 5 nm. It is confirmed that the metal ions (Fe, V, Co, and Ni) are doped into MnO₂, improving the conductivity of MnO₂. The doped MnO₂ ultrathin nanosheet/CFP and the IrO₂/CFP composite electrodes for OER achieve a low overpotential of 390 and 245 mV to reach 10 mA cm^?2 in 1 m KOH, respectively. The potential of the doped composite electrode for long‐term OER at a constant current density of 20 mA cm^?2 is much lower than that of the pure MnO₂ composite electrode.     

3D Self‐Supported Fe‐Doped Ni2P Nanosheet Arrays as Bifunctional Catalysts for Overall Water Splitting

The development of highly efficient bifunctional electrocatalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is crucial for improving the efficiency of overall water splitting, but still remains challenging issue. Herein, 3D self‐supported Fe‐doped Ni₂P nanosheet arrays are synthesized on Ni foam by hydrothermal method followed by in situ phosphorization, which serve as bifunctional electrocatalysts for overall water splitting. The as‐synthesized (Ni_0.33Fe_0.67)₂P with moderate Fe doping shows an outstanding OER performance, which only requires an overpotential of ≈230 mV to reach 50 mA cm^?2 and is more efficient than the other Fe incorporated Ni₂P electrodes. In addition, the (Ni_0.33Fe_0.67)₂P exhibits excellent activity toward HER with a small overpotential of ≈214 mV to reach 50 mA cm^?2. Furthermore, an alkaline electrolyzer is measured using (Ni_0.33Fe_0.67)₂P electrodes as cathode and anode, respectively, which requires cell voltage of 1.49 V to reach 10 mA cm^?2 as well as shows excellent stability with good nanoarray construction. Such good performance is attributed to the high intrinsic activity and superaerophobic surface property.     

High-Density Atomic Fe–N4/C in Tubular,Biomass-Derived,Nitrogen-Rich Porous Carbon as Air-Electrodes for Flexible Zn–Air Batteries

Developing low-cost single-atom catalysts (SACs) with high-density active sites for oxygen reduction/evolution reactions (ORR/OER) are desirable to promote the performance and application of metal–air batteries. Herein, the Fe nanoparticles are precisely regulated to Fe single atoms supported on the waste biomass corn silk (CS) based porous carbon for ORR and OER. The distinct hierarchical porous structure and hollow tube morphology are critical for boosting ORR/OER performance through exposing more accessible active sites, providing facile electron conductivity, and facilitating the mass transfer of reactant. Moreover, the enhanced intrinsic activity is mainly ascribed to the high Fe single-atom (4.3 wt.%) loading content in the as-synthesized catalyst.Moreover, the ultra-high N doping (10 wt.%) can compensate the insufficient OER performance of conventional Fe N C catalysts. When as-prepared catalysts are assembled as air-electrodes in flexible Zn–air batteries, they perform a high peak power density of 101 mW cm⁻², a stable discharge–charge voltage gap of 0.73 V for >44 h, which shows a great potential for Zinc–air battery. This work provides an avenue to transform the renewable low-cost biomass materials into bifunctional electrocatalysts with high-density single-atom active sites and hierarchical porous structure.     

Rapid Synthesis of Various Electrocatalysts on Ni Foam Using a Universal and Facile Induction Heating Method for Efficient Water Splitting

Electrocatalytic water splitting for the production of hydrogen proves to be effective and available. In general, the thermal radiation synthesis usually involves a slow heating and cooling process. Here, a high-frequency induction heating (IH) is employed to rapidly prepare various self-supported electrocatalysts grown on Ni foam (NF) in liquid- and gas-phase within 1–3 min. The NF not only serves as an in situ heating medium, but also as a growth substrate. The as-synthesized Ni nanoparticles anchored on MoO₂ nanowires supported on NF (Ni-MoO₂/NF-IH) enable catalysis of hydrogen evolution reaction (HER), showing a low overpotential of −39 mV (10 mA cm⁻²) and maintaining the stability of 12 h in alkaline condition. Moreover, the NiFe layered double hydroxide (NiFe LDH/NF-IH) is also synthesized via IH and affords outstanding oxygen evolution reaction (OER) activity with an overpotential of 246 mV (10 mA cm⁻²). The Ni-MoO₂/NF-IH and NiFe LDH/NF-IH are assembled to construct a two-electrode system, where a small cell voltage of ≈1.50 V enables a current density of 10 mA cm⁻². More importantly, this IH method is also available to rapidly synthesize other freestanding electrocatalysts on NF, such as transition metal hydroxides and metal nitrides.     

Fe?N?C Electrocatalysts with Densely Accessible Fe?N4 Sites for Efficient Oxygen Reduction Reaction

The development of iron and nitrogen co-doped carbon (Fe N C) electrocatalysts for the oxygen reduction reaction (ORR) in proton-exchange membrane fuel cells (PEMFCs) is a grand challenge due to the low density of accessible Fe N₄ sites. Here, an in situ trapping strategy using nitrogen-rich molecules (e.g., melamine, MA) is demonstrated to enhance the amount of accessible Fe N₄ sites in Fe N C electrocatalysts. The melamine molecules can participate in the coordination of Fe ions in zeolitic imidazolate frameworks to form Fe N₆ sites within precursors. These Fe N₆ sites are then converted into atomically dispersed Fe N₄ sites during a pyrolytic process. Remarkably, the Fe N C/MA exhibits a high single-atom Fe content (3.5 wt.%), a large surface area (1160 m² g⁻¹), and a high density of accessible FeN₄ sites (45.7 × 10¹⁹ sites g⁻¹). As a result, Fe N C/MA shows a much enhanced ORR activity with a half-wave potential of 0.83 V (vs the reversible hydrogen electrode) in a 0.5 m H₂SO₄ electrolyte solution and a good performance in a PEMFC system with an activity of 80 mA cm⁻² at 0.8 V under 1.0 bar H₂/air. This work offers a promising approach toward high-performance carbon-based ORR electrocatalysts.     

Highly Boosted Reaction Kinetics in Carbon Dioxide Electroreduction by Surface-Introduced Electronegative Dopants

Effectively improving the selectivity while reducing the overpotential over the electroreduction of CO₂ (CO₂ER) has been challenging. Herein, electronegative N atoms and coordinatively unsaturated Ni N₃ moieties co-anchored carbon nanofiber (Ni N₃ NCNFs) catalyst via an integrated electrospinning and carbonization strategy are reported. The catalyst exhibits a maximum CO Faradaic efficiency (F.E.) of 96.6%, an onset potential of −0.3 V, and a low Tafel slope of 71 mV dec⁻¹ along with high stability over 100 h. Aberration corrected scanning transmission electron microscopy, X-ray absorption spectroscopy, and X-ray photoelectron spectroscopy identify the atomically dispersed Ni N₃ sites with Ni atom bonded by three pyridinic N atoms. The existence of abundant electronegative N dopants adjoin the Ni N₃ centers in Ni N₃ NCNFs. Theoretical calculations reveal that both, the undercoordinated Ni N₃ centers and their first neighboring C atoms modified by extra N dopants, display the positive effect on boosting CO₂ adsorption and water dissociation processes, thus accelerating the CO₂ER kinetics process. Furthermore, a designed Zn CO₂ battery with the cathode of Ni N₃ NCNFs delivers a maximum power density of 1.05 mW cm⁻² and CO F.E. of 96% during the discharge process, thus providing a promising approach to electric energy output and chemical conversion.     

Directional Reconstruction of Iron Oxides to Active Sites for Superior Water Oxidation

Rationally constructing and manipulating the in situ formed catalytically active surface of catalysts remains a tremendous challenge for a highly efficient water electrolysis. Herein, an anion and cation co-induced strategy is presented to modulate in situ catalyst dissolution-redeposition and to achieve the directional reconstruction of Zn and S co-doped Fe₂O₃ and Fe₃O₄ on iron foams (Zn,S-Fe₂O₃-Fe₃O₄/IF), for oxygen evolution reaction (OER). Benefiting from Zn, S co-doping and the presence of Fe₃O₄, a directionally reconstructed surface is obtained. The Fe₂O₃ in the Zn,S-Fe₂O₃-Fe₃O₄/IF is directionally reconstructed into FeOOH (Zn,S-Fe₃O₄-FeOOH/IF), in which the S leaching promotes the Fe dissolution and the Zn co-deposition regulates the activity of the obtained FeOOH. Moreover, the presence of Fe₃O₄ provides a stable site for FeOOH deposition, and thus causes more FeOOH active components to be formed. Directionally reconstructed Zn,S-Fe₃O₄-FeOOH/IF outperformes many state-of-the-art OER catalysts and demonstrates a remarkable stability. The experimental and density functional theory (DFT) calculation results show that the introduction of Zn-doped FeOOH with abundant oxygen vacancies through directional reconstruction has activated lattice O atoms, facilitating the OER process on the heterojunction surface following the lattice oxygen mechanism (LOM) pathway. This work makes a stride in co-induced strategy modulating directional reconstruction.     

Fe3O4‐Decorated Co9S8 Nanoparticles In Situ Grown on Reduced Graphene Oxide: A New and Efficient Electrocatalyst for Oxygen Evolution Reaction

Cobalt sulfide materials have attracted enormous interest as low‐cost alternatives to noble‐metal catalysts capable of catalyzing both oxygen reduction and oxygen evolution reactions. Although recent advances have been achieved in the development of various cobalt sulfide composites to expedite their oxygen reduction reaction properties, to improve their poor oxygen evolution reaction (OER) activity is still challenging, which significantly limits their utilization. Here, the synthesis of Fe₃O₄‐decorated Co₉S₈ nanoparticles in situ grown on a reduced graphene oxide surface (Fe₃O₄@Co₉S₈/rGO) and the use of it as a remarkably active and stable OER catalyst are first reported. Loading of Fe₃O₄ on cobalt sulfide induces the formation of pure phase Co₉S₈ and highly improves the catalytic activity for OER. The composite exhibits superior OER performance with a small overpotential of 0.34 V at the current density of 10 mA cm^?2 and high stability. It is believed that the electron transfer trend from Fe species to Co₉S₈ promotes the breaking of the Co–O bond in the stable configuration (Co–O–O superoxo group), attributing to the excellent catalytic activity. This development offers a new and effective cobalt sulfide‐based oxygen evolution electrocatalysts to replace the expensive commercial catalysts such as RuO₂ or IrO₂.     

Self-Reconstruction of Single-Atom-Thick A Layers in Nanolaminated MAX Phases for Enhanced Oxygen Evolution

M_n+1AX_n (MAX) phases are a family of nanolaminated ternary carbide/nitride, which are generally investigated as high-safety structural materials, but their direct applications on electrocatalysis is still far from reality. Here, it is shown that by taking the advantages of self-reconstruction, a unique class of MAX phases of V₂(Sn, A)C (A = Ni, Co, Fe) can be adopted as efficient catalysts for oxygen evolution reaction (OER). The specific single-atomic-thick (Sn, A) layers within V–C networks in V₂(Sn, A)C are highly flexible to react with electrolyte. As a result, the V₂(Sn, Ni)C (VSNC) can maintain bulk crystalline structure, and merely encounter surface reconstruction to generate Ni-based oxyhydroxide accompanying with the self-doping of V and Sn elements under alkaline OER condition. The surface-reconstructed VSNC exhibits significantly enhanced OER performance to that of reconstructed Ni nanopowder and V₂SnC. Density functional theory simulations indicate that the doping of Sn/V into γ-NiOOH leads to the change of reaction pathway of alkaline OER, while the introduction of V can reduce the reaction barrier to facilitate the OER process. This study exhibits a new functionality of a unique MAX phase toward OER, which puts forward the potential applications of MAX phase materials in electrocatalysis and beyond.