Modification of Manganese Dioxide to Achieve Activity–Stability Trade-Off for Acidic Oxygen Evolution Reaction: A Critical Review

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The acidic oxygen evolution reaction (OER) is a critical process in proton exchange membrane water electrolysis (PEMWE) for green hydrogen production. However, the harsh acidic and oxidative condition poses significant challenges to the achievement of activity–stability trade-off for electrocatalysts. While noble metal oxides (IrO₂, RuO₂) are always the benchmark materials, the high cost and scarcity hinder their widespread application. Manganese dioxide (MnO₂) has emerged as a promising non-noble candidate due to its exceptional corrosion resistance, cost-effectiveness, and unique self-healing capability. Nevertheless, its practical utility is limited by modest intrinsic activity and dissolution at low pH values or high potentials. This review comprehensively summarizes the recent advances in modification strategies to enhance the OER performance of MnO₂-based catalysts in acidic media. The OER mechanisms in acid are first delineated with a specific focus on the distinct catalytic pathway of MnO₂. Subsequently, various engineering approaches, including phase engineering, composite engineering (with noble/non-noble metals), atomic array construction, and heteroatom doping, are systematically elaborated. These strategies are discussed in terms of how they optimize the electronic structure, enhance conductivity, stabilize the MnO₂ lattice, and reinforce metal–support interactions to boost both activity and durability. Finally, a perspective on the remaining challenges and future research directions is provided, emphasizing the need for mechanistic insights, standardized evaluation protocols, and the transition toward practical PEMWE device integration.