Non-Iridium-Based Electrocatalysts for the Acidic Oxygen Evolution Reaction: Progress and Perspectives.

The oxygen evolution reaction (OER) in acidic media remains a major bottleneck for proton exchange membrane water electrolysis (PEMWE), demanding catalysts with both high activity and durability. Although Ir-based materials exhibit excellent performance, their scarcity and high cost hinder large-scale applications. Recent advances are focused on non-Ir-based catalysts, including Ru-based systems, transition-metal oxides, and metal-free materials, where strategies such as defect engineering, heteroatom doping, interface modulation, and high-entropy design can effectively tune electronic structures for better performance with improved stability. Active sites and reaction intermediates under working conditions are explored for getting deeper insights into the mechanism, using advanced in situ/operando characterization techniques. Nevertheless, under harsh acidic conditions, mental dissolution and structural degradation of catalysts still limit long-term operation. Therefore, future efforts will integrate AI-driven high-throughput screening to accelerate the rational design of catalysts while simultaneously optimizing PEM electrolyzer architectures and operando characterization techniques. Furthermore, developing sustainable seawater electrolysis technology could promote acidic OER toward large-scale green hydrogen production.