Unraveling Surface Reconstruction During Oxygen Evolution Reaction on the Defined Spinel Oxide Surface

Abstract The reconstructed surface structure of Co‐based spinel oxides serves as the active site for oxygen evolution reaction (OER). However, the structural complexity of spinel oxides and surface dynamics during the OER hinder the understanding of the reconstruction mechanism and electronic structure of the active site. In this study, spinel Co₃O₄@(CoFeV)₃O₄ nanocube (CoFeV) is reported, a (001) facet‐defined spinel oxide comprising Co, Fe, and V deposited on the Co₃O₄ nanocube template to exclude facet‐dependent factors. Introducing highly dissoluble V cations accelerates the reconstruction process to enhance the electrocatalytic activity. CoFeV exhibited enhanced electrocatalytic activity (266 mV at 10 mA cm⁻² in 1 M KOH) and durability (maintained stable electrocatalytic activity during a 200 h chronopotentiometry (CP) test at 100 mA cm⁻²) with significantly enlarged electrochemically active surface area (ECSA). The experimental and theoretical results demonstrated that V dissolution during catalysis induced oxygen vacancies, accelerating the surface reconstruction to highly active oxyhydroxide. Consequently, the anion exchange membrane water electrolyzer (AEMWE) of CoFeV as the anode exhibited a remarkable performance of 6.19 A cm⁻² at 2.0 V_cell in 1 M KOH and robust durability for 96 h at a constant current density of 500 mA cm⁻².