Transition Metal Oxide Catalysts for Acidic Oxygen Evolution: Current Status and Key Strategies Toward Efficient PEM Water Electrolysis

ABSTRACT Proton exchange membrane water electrolysis (PEMWE) is a promising technology for green hydrogen production due to its high efficiency, compact design, and flexible operation. However, the reliance on noble metal‐based anode catalysts significantly increases hydrogen production costs. Transition metal oxides have emerged as alternatives for the acidic oxygen evolution reaction (OER) because of their diverse compositions, tunable structures, and lower cost. This review summarizes recent advances in transition metal oxide catalysts beyond pure IrO 2 , RuO 2 , and their mixtures. Fundamental OER mechanisms, including the adsorbate evolution mechanism, lattice oxygen mechanism, and oxide pathway mechanism, are introduced, with emphasis on their roles in regulating catalytic activity and stability. Representative catalyst systems such as spinels, perovskites, pyrochlores, dioxides, and high entropy oxides are systematically reviewed, highlighting performance enhancement strategies including heterostructure construction, elemental doping, and defect engineering. Emerging concepts such as reaction pathway engineering, corrosion suppression, and dynamic structural stability are discussed as effective approaches to overcoming the trade‐off between activity and stability. Finally, current challenges and future perspectives are outlined, with emphasis on artificial intelligence‐assisted catalyst design, characterization optimization, scalable synthesis, and standardized industrial evaluation, to accelerate the practical deployment of advanced acidic OER catalysts in sustainable hydrogen production.