Strontium Leaching Precedes SrIrO3 Dissolution During Electrochemical Water Oxidation

Mechanistic studies of oxide electrocatalysts for heterogeneous water oxidation have been primarily focused on understanding the origins of activity. Despite encouraging progress, achieving long-term stability remains an important goal for their industrial implementation. In this work, we study the degradation pathways of a highly active SrIrO3 electrocatalyst during the oxygen evolution reaction (OER). SrIrO3 serves as a model system for perovskite AMO3 oxides as it can exhibit both A-cation leaching and transition metal (TM) oxide dissolution. Employing epitaxial SrIrO3 thin films, we explore the electrolyte- and potential-dependent leaching of Sr from the perovskite structure by following these processes through operando electrochemical atomic force microscopy (EC-AFM). Dissolution was imaged and quantified at the nanometer scale. We show that Sr leaching results in the in-situ formation of Sr1-xIrOy layer, with the leaching rate controlled via electrolyte composition. Crucially, Sr leaching occurs at a potential > 0.5V lower than that for transition metal oxide dissolution. Our study demonstrates that suppression of the A-site leaching is crucial for improving the overall stability of perovskite oxide during electrocatalysis.