Iridium Selenium Oxyhydroxide Shell for Polymer Electrolyte Membrane Water Electrolyzer with Low Ir Loading

Low-Ir electrocatalysts are crucial for developing large-scale polymer-electrolyte-membrane water electrolysis (PEMWE) facilities, which are necessary to advance the hydrogen economy. However, the performance and durability of low-Ir electrocatalysts are unsatisfactory. To address this issue, we prepared selenium-modified Ir nanoparticles on high-crystalline-carbon (HCC) supports. The introduction of HCC supports effectively reduced Ir usage, and Se incorporation mitigated Ir degradation. Se nucleophiles suppressed the electrochemical oxidation of Ir, leading to the formation of a unique nanostructure featuring an ultrathin IrO_xH_ySe_z shell and a crystalline Ir core. Theoretical calculations indicated that the electronic structure of Ir and its binding affinity with *O were modified, thereby enhancing the catalytic activities. Ir-IrO_xH_ySe_z/HCC exhibited outstanding PEMWE performances (Ir-mass specific power of 23.69 kW·gIr^-1; durability for 370 h) with a small amount of Ir (0.05 mg·cm^-2). Thus, employing a carbon support and nucleophile-induced nanostructures can serve as a strategy to ensure long-term PEMWE performance while reducing Ir usage.