Pathways to Low-Iridium Loading in Proton Exchange Membrane Water Electrolyzer Anodes: From Catalyst Design to Catalyst Layer Integration

Proton exchange membrane water electrolyzers (PEMWEs) are a promising technology for large-scale green hydrogen production; however, the high cost and scarcity of iridium (Ir) remain major obstacles to commercialization. Reducing Ir loading while maintaining catalytic activity and durability is therefore essential to achieving cost-effective hydrogen production. Among various strategies, the development of supported oxygen evolution reaction catalysts has emerged as a particularly effective approach. By anchoring Ir nanostructures onto acid-stable, high-surface-area metal oxide supports, such as TiO 2, SnO 2, and Ta 2 O 5, researchers have demonstrated enhanced catalyst utilization, improved stability, and significantly reduced precious metal content. These supports not only disperse active sites more effectively but also promote strong metal−support interactions, enabling robust performance under harsh PEMWE operating conditions. This perspective highlights recent advances in structure engineering, oxidation state modulation, and support material design that collectively enable the fabrication of low-Ir anodes with high efficiency. This work further focuses on the integration of these supported catalysts into membrane electrode assemblies (MEAs) and proposes future research directions aimed at achieving the Ir loading target (0.125 mg Ir cm −2 ) suggested by the U.S. Department of Energy. Together, these innovations offer a path forward toward scalable and economically viable PEMWE systems for a sustainable hydrogen economy.