Research Progress on Regulating the Alkaline OER Performance of Transition Metal-Based Catalysts Through Vacancy Defect Engineering

The oxygen evolution reaction (OER) is the rate-limiting step in alkaline water electrolysis for hydrogen production. Owing to their earth abundance and high intrinsic activity, transition metal-based catalysts (TMBCs) have emerged as promising alternatives to noble-metal catalysts, with defect engineering recognized as an effective strategy for enhancing OER performance. This review systematically summarizes recent advances in regulating alkaline OER activity of TMBCs through vacancy defects, including anion vacancies, cation vacancies, and divacancies. First, the alkaline OER mechanism, key performance evaluation parameters, and activity descriptors are briefly introduced. The formation mechanisms and regulation strategies of different vacancy types are discussed, with emphasis on how vacancy defects enhance OER performance by modulating electronic structures, optimizing active sites, and tuning adsorption–desorption behaviors of reaction intermediates. In addition, the advantages and application scenarios of various characterization techniques for vacancy defects are summarized. Finally, current challenges are identified, and future research directions are proposed. This review provides theoretical and practical references for the rational design of high-performance transition metal-based OER catalysts and the large-scale advancement of alkaline water electrolysis for hydrogen production.