Activating Oxygen Radical Coupling on Face-Shared IrO₆ Dimer Through Enhanced Electronic Coupling for Acidic Water...

Driving the oxygen evolution reaction (OER) through an oxide‑path mechanism (OPM) offers an appealing route to achieve simultaneously high activity and durability, yet rational modulation of dual‑metal active sites remain elusive. Here, we realize an unprecedented switch from the conventional adsorbate evolution mechanism (AEM) to OPM in 6H-SrIrO₃ via partial La substitution. Electronic structure analysis reveals that La incorporation strengthens electronic coupling across face-sharing IrO₆ dimers via Ir-O-Ir bridge. Consequently, these dimers, characterized by short Ir-Ir interatomic distances, are activated as dual-metal centers that enable oxygen radical coupling via the OPM pathway. Benefiting from this mechanistic transition, the optimized 2%La-SrIrO₃ catalyst surpasses the activity-stability trade‑off, exhibiting a low overpotential and exceptional durability over 1900 h at 1 A cm^-2 in a proton exchange membrane (PEM) electrolyzer. This work unveils a mechanistic design paradigm for robust OER electrocatalysts operating under acidic conditions.