Sustainable Low-Valent Iridium Active Sites in Rhenium Doped Perovskite Iridates for Efficient Acidic Oxygen Evolution Reaction via Hybridized Reaction Pathways.

Proton exchange membrane water electrolysis (PEMWE) is a promising route for sustainable hydrogen production, yet its adoption is limited by the scarcity and cost of Ir-based oxygen evolution reaction (OER) catalysts. Here, we first report that a Re-doped SrZrxIr1-xO3 (Re-SZIO) perovskite iridate exhibits outstanding OER performance in acid media, combining a low overpotential (250 mV at 10 mA cm-2) and high Ir mass activity (> 1,300 A gIr-1) with robust durability. High-valent Re doping stabilizes an active low-valent Ir species in Re-SZIO, suppresses overoxidation, and promotes sustainable formation of active sites. Combinational mechanistic studies using in situ spectroscopy and grand canonical density functional theory (GC-DFT) with microkinetic modeling reveal that dynamic Re-Ir-O interactions open an additional oxide path mechanism (OPM) branch alongside the conventional adsorbate evolution mechanism (AEM), yielding a hybrid pathway in which the OPM contributes at low overpotentials while the AEM remains dominant at higher overpotentials. This work demonstrates a viable strategy for designing robust, efficient, and low-Ir based OER catalysts via precise electronic modulation of both the reaction pathway and the framework stability.