Small, Narrowly Distributed Iridium Nanoparticles Supported on Indium Tin Oxide for Efficient Anodic Water Oxidation Dmitry Lebedev Christophe Copéret 10.1021/acsaem.8b01724.s001 https://acs.figshare.com/articles/journal_contribution/Small_Narrowly_Distributed_Iridium_Nanoparticles_Supported_on_Indium_Tin_Oxide_for_Efficient_Anodic_Water_Oxidation/7471466 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<sub>NP</sub>–ITO material is very active and stable in water oxidation, reaching a current of 10 A g<sub>Ir</sub><sup>–1</sup> 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. 2018-12-13 00:00:00 ITO particle surface water oxidation OER efficiency X-ray photoelectron spectroscopy studies Indium Tin Oxide anodic water oxidation catalysts surface Ir-oxo-hydroxide layer immobilizing 1.5 nm Ir nanoparticles conductive indium tin oxide support OER conditions Iridium Nanoparticles NP layer forms iridium particles 1.470 V vs RHE electrochemical tests Efficient Anodic Water Oxidation resolution electron microscopy electrode design Ir content metal content acidic media