Strontium Doped IrO_x Triggers Direct O-O Coupling to Boost Acid Water Oxidation Electrocatalysis

The discovery of efficient and stable electrocatalysts for the oxygen evolution reaction (OER) in acidic conditions is crucial for the commercialization of proton-exchange membrane water electrolyzers. In this work, we propose a Sr(OH)₂-assisted method to fabricate a (200) facet highly exposed strontium-doped IrO_x catalyst to provide available adjacent iridium sites with lower Ir-O covalency. This design facilitates direct O-O coupling during the acidic water oxidation process, thereby circumventing the high energy barrier associated with the generation of *OOH intermediates. Benefiting from this advantage, the resulting Sr-IrO_x catalyst exhibits an impressive overpotential of 207 mV at a current density of 10 mA cm^-2 in 0.5 M H₂SO₄. Furthermore, a PEMWE device utilizing Sr-IrO_x as the anodic catalyst demonstrates a cell voltage of 1.72 V at 1 A cm^-2 and maintains excellent stability for over 500 hours. Our work not only provides guidance for the design of improved acidic OER catalysts but also encourages the development of iridium-based electrocatalysts with novel mechanisms for other electrocatalytic reactions.