Self‐Reconstructed Spinel with Enhanced SO ₄ ²⁻ Adsorption and Highly Exposed Co ³⁺ From Heterostructure Boosts Activity and Stability at High Current Density for Overall Water Splitting

Abstract Developing overall water splitting non‐noble metal electrocatalysts achieving long‐term stability with high activity at industrial‐grade current density remains challenging. Herein, a self‐reconstruction strategy of Co ₉ S ₈ ‐Ni ₃ S ₂ /NCF is employed to fabricate Ni _x Co _3‐x O ₄ ‐Ov‐ in which partial Co is replaced by Ni in the structure. The reconstructed Ni _x Co _3‐x O ₄ ‐Ov can enhance the adsorbing ability of leached from the initial phase compared with Co spinel, achieving exceeding 1000‐h oxygen evolution reaction (OER) and 600‐h overall water splitting stability at 1000 mA cm ⁻² with excellent activity. In situ Raman and X‐ray photoelectron spectroscopy (XPS) results indicate that partial substitution of Ni for Co atoms enhances the adsorption capacity on the reconstructed Ni _x Co _3‐x O ₄ ‐Ov, facilitating the formation of high‐density Co ³⁺ active sites on (400) that expedited interfacial electron transfer at high current densities. Density functional theory (DFT) calculations reveal that the adsorption of leached stabilizes surface oxygen vacancies and optimizes the adsorption energy of intermediates, thereby improving both stability and catalytic performance. The findings provide new insights into overcoming the activity‐stability trade‐off and contribute to the strategy for the design of electrocatalysts for long‐term water splitting at industrial‐grade current densities.