Reactivity and Stability of Reduced Ir-Weight TiO2-Supported Oxygen Evolution Catalysts for Proton Exchange Membrane (PEM) Water Electrolyzer Anodes

Reducing the iridium demand in Proton Exchange Membrane Water Electrolyzers (PEM WE) is a critical priority for the green hydrogen industry. This study reports the discovery of a TiO2-supported Ir@IrO(OH)x core–shell nanoparticle catalyst with reduced Ir content, which exhibits superior catalytic performance for the electrochemical oxygen evolution reaction (OER) compared to a commercial reference. The TiO2-supported Ir@IrO(OH)x core–shell nanoparticle configuration significantly enhances the OER Ir mass activity from 8 to approximately 150 A gIr–1 at 1.53 VRHE while reducing the iridium packing density from 1.6 to below 0.77 gIr cm–3. These advancements allow for viable anode layer thicknesses with lower Ir loading, reducing iridium utilization at 70% LHV from 0.42 to 0.075 gIr kW–1 compared to commercial IrO2/TiO2. The identification of the Ir@IrO(OH)x/TiO2 OER catalyst resulted from extensive HAADF-EDX microscopic analysis, operando XAS, and online ICP-MS analysis of 30–80 wt % Ir/TiO2 materials. These analyses established correlations among Ir weight loading, electrode electrical conductivity, electrochemical stability, and Ir mass-based OER activity. The activated Ir@IrO(OH)x/TiO2 catalyst–support system demonstrated an exceptionally stable morphology of supported core–shell particles, suggesting strong catalyst–support interactions (CSIs) between nanoparticles and crystalline oxide facets. Operando XAS analysis revealed the reversible evolution of significantly contracted Ir–O bond motifs with enhanced covalent character, conducive to the formation of catalytically active electrophilic OI– ligand species. These findings indicate that atomic Ir surface dissolution generates Ir lattice vacancies, facilitating the emergence of electrophilic OI– species under OER conditions, while CSIs promote the reversible contraction of Ir–O distances, reforming electrophilic OI– and enhancing both catalytic activity and stability.