Small, Narrowly Distributed Iridium Nanoparticles Supported on Indium Tin Oxide for Efficient Anodic Water Oxidation

Decreasing the noble metal content while maintaining high catalytic activity is a critical requirement for the development of efficient anodic water oxidation catalysts in acidic media. In the present work, we developed a method for immobilizing 1.5 nm Ir nanoparticles on a conductive indium tin oxide support. In addition to having a low Ir content of 4.1 wt %, the obtained Ir_NP–ITO material is very active and stable in water oxidation, reaching a current of 10 A g_Ir^–1 at 1.470 V vs RHE. Our electrode design allows for convenient analysis of the catalyst after the electrochemical tests. Employing high resolution electron microscopy, we show that under the OER conditions, the core of iridium particles stays metallic, while amorphous layer forms on the particle surface, which we attribute to Ir-oxo-hydroxide based on our X-ray photoelectron spectroscopy studies. The surface Ir-oxo-hydroxide layer is responsible for the high OER efficiency of the supported catalyst.