MoO ₂ ‐Mediated Ni─Fe Bond Contraction and Electronic Modulation in Ni ₃ Fe Alloy for Efficient Water Electrolysis at High‐Current‐Densities

Abstract

Abstract Ni 3 Fe alloy electrocatalysts show promising activity for water electrolysis but are limited by sluggish hydrogen/oxygen evolution reaction (HER/OER) kinetics, and inefficient gas‐liquid mass transfer under high‐current‐densities. Here, a superhydrophilic/superaerophobic 3D carbonized wood‐loaded Ni 3 Fe‐MoO 2 (Ni 3 Fe/MoO 2 /CW) heterojunction is designed to address these challenges. X‐ray absorption fine structure (XAFS) and theoretical calculations reveal that the introduction of MoO 2 shortens the Ni─Fe bond length, induces electron transfer from Ni 3 Fe to MoO 2 , and regulates the d ‐band center of Ni/Fe. These optimized Ni─Fe bonds and electronic structure enhance H─OH bond dissociation and H* adsorption/desorption, thereby accelerating the HER Volmer‐Heyrovsky step. Simultaneously, for the OER adsorption evolution mechanism on Ni 3 Fe (1.462 eV), the strengthened Ni─O─Mo bond on Ni 3 Fe‐MoO 2 heterojunction reduces the energy barrier (1.092 eV) of the rate‐determining step, significantly improving catalytic efficiency. Thus, Ni 3 Fe/MoO 2 /CW displays good activity (HER: η −10/−750 = 45/342 mV; OER: η 300/1000 = 251/306 mV). Notably, the large specific area of Ni 3 Fe/MoO 2 /CW from its nanosheet‐particle structure enhances the electrolyte/bubble exchange at the gas‐liquid‐solid three‐phase interface, enabling stable operation at 1000 mA cm −2 for 24 h in an anion exchange membrane electrolyzer. This work demonstrates a MoO 2 ‐driven strategy for electronic modulation and metal bond regulation to boost HER/OER kinetics, advancing Ni 3 Fe‐based catalysts toward practical high‐current‐densities water electrolysis.