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

Abstract

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.