Building Metal–Oxygen Connectivity in Amorphous Iridium Oxide through Electrochemical Cycling in Acid

The development of oxygen evolution reaction (OER) catalysts has been hindered by the high overpotential requirements, challenges in catalyst stability, and the complexity of OER mechanisms. Under water oxidation conditions, multiple concurrent processes, such as catalyst dissolution and surface reconstruction, further complicate mechanistic understandings. One factor that makes studies of water oxidation mechanisms especially difficult is the dynamic nature of the catalytic structure under reaction conditions. Herein, we report the observation of a stabilization effect of an amorphous iridium oxide (IrOx) catalyst under water oxidation conditions. The effect was revealed to be caused by improved connectivity between neighboring Ir and O atoms on the surface. The reaction was found to proceed in parallel to the oxidation of H2O and was only observed under potentials above the onset of water oxidation. X-ray photoelectron spectroscopy, X-ray absorption spectroscopy, and density functional theory calculations further confirmed this understanding. The results shed light on the competing reaction pathways once an active metal center is activated and highlight the favorable outcomes by improved connectivity for water oxidation catalysis.