High‐Performance Supported Iridium Oxohydroxide Water Oxidation Electrocatalysts

Abstract

Abstract The synthesis of a highly active and yet stable electrocatalyst for the anodic oxygen evolution reaction (OER) remains a major challenge for acidic water splitting on an industrial scale. To address this challenge, we obtained an outstanding high‐performance OER catalyst by loading Ir on conductive antimony‐doped tin oxide (ATO)‐nanoparticles by a microwave (MW)‐assisted hydrothermal route. The obtained Ir phase was identified by using XRD as amorphous (XRD‐amorphous), highly hydrated Ir III/IV oxohydroxide. To identify chemical and structural features responsible for the high activity and exceptional stability under acidic OER conditions with loadings as low as 20 μg Ir cm −2 , we used stepwise thermal treatment to gradually alter the XRD‐amorphous Ir phase by dehydroxylation and crystallization of IrO 2 . This resulted in dramatic depletion of OER performance, indicating that the outstanding electrocatalytic properties of the MW‐produced Ir III/IV oxohydroxide are prominently linked to the nature of the produced Ir phase. This finding is in contrast with the often reported stable but poor OER performance of crystalline IrO 2 ‐based compounds produced through more classical calcination routes. Our investigation demonstrates the immense potential of Ir oxohydroxide‐based OER electrocatalysts for stable high‐current water electrolysis under acidic conditions.