Mechanistic Study of IrO Dissolution during the Electrocatalytic Oxygen Evolution Reaction.

Understanding the mechanistic interplay between the activity and stability of water splitting electrocatalysts is crucial for developing efficient and durable water electrolyzers. Ir-based materials are among the best catalysts for the oxygen evolution reaction (OER) in acidic media, but their degradation mechanisms are not completely understood. Here, through first-principles calculations we investigate iridium dissolution at the IrO(110)/water interface. Simulations reveal that the surface-bound IrOOH species formed upon iridium dissolution should be thermodynamically stable in a relatively wide potential window undergoing transformations into Ir (as IrO) at high anodic potentials and Ir (as Ir(OH)) at low anodic potentials. The identified high-valence surface-bound dissolution intermediates of Ir are determined to display greater OER activities than the pristine IrO(110) surface in agreement with the experimentally observed high activity of an amorphous hydrated IrO surface layer. Combined with recent experimental results, our simulations illuminate the mechanistic details of the degradation mechanism of IrO and how it couples to electrocatalytic OER.