Seed-Mediated Growth of Mesoporous Pyrochlore for Efficient and Durable Acidic Oxygen Evolution

Proton exchange membrane water electrolysis (PEMWE) is a promising route to hydrogen, yet sluggish anodic oxygen evolution reaction (OER) kinetics and durability limitations in acidic media still constrain device efficiency and lifetime. Here we report Y2Ir1.2Ru0.8O7, a pyrochlore catalyst in which dual active sites are precisely constructed at the B site via seed-mediated growth, enabling concurrent high activity and durability for acidic OER. The mesoporous nanosphere architecture creates a superhydrophilic, high surface area microenvironment that improves mass transport and facilitates bubble detachment. In 0.1 M HClO4, the catalyst requires only 227 mV overpotential at 10 mA cm–2 and the cell voltage rises by about 20 mV after 1200 h of continuous operation. Operando characterization (FTIR/18O–DEMS) combined with DFT results indicates that the OER on Y2Ir1.2Ru0.8O7 follows an oxide pathway mechanism (OPM), thereby validating the feasibility of OPM at B site dual active centers in the pyrochlore structure. Notably, Y2Ir1.2Ru0.8O7 supports direct coupling of *O–*O radicals during OER, thereby avoiding the formation of *OOH. A PEMWE cell using Y2Ir1.2Ru0.8O7 as the anode maintains stability for more than 200 h at 2 A cm–2, indicating potential for scale up. This work provides a generalizable structure-mechanism codesign strategy for high performance, long-lived acidic OER catalysts tailored to PEMWE.