Cation‐Vacancy‐Induced Reinforced Electrochemical Surface Reconstruction on Spinel Nickel Ferrite for Boosting Water Oxidation

Abstract Spinel oxides still exhibit unsatisfactory electrocatalytic performance toward oxygen evolution reaction (OER) given their low intrinsic activity, poor electronic conductivity, and limited exposure of reaction sites. Defect engineering has garnered intensive attention and become a promising strategy to enhance the reaction kinetics. In this work, spinel NiFe₂O₄ nanospheres with rich nickel vacancies are prepared via simple one‐pot hydrothermal synthesis. Combined electrochemical measurements and in situ Raman characterization prove that a relatively higher degree of electrochemical surface reconstruction is realized after the introduction of nickel vacancies in NiFe₂O₄, in addition to boosted OER electrocatalytic performance. Further theoretical calculations also reveal that the cation‐vacancy‐induced effect can reduce the difficulty for surface reconstruction by increasing the octahedral nickel‐oxygen covalency in nickel ferrite. Contributed to the great structural flexibility and optimized electronic structure of the pre‐catalyst, the reconstructed electrocatalyst presents desirable OER performance, accompanied by long durability in alkaline solution. This work provides a sound strategy to intensify surface reconstruction on spinel oxides and design electrocatalysts with high efficiency toward water oxidation.