Electrochemical characterization of sol-gel formed Ir metal nanoparticles

Electrochemical studies of a sol-gel (SG) derived Ir-containing film have shown conclusively that films formed by air drying or heating at temperatures below ca. 500 degrees C are metallic in nature, exhibiting the typical signature of Ir metal. Both compact oxide formation and reduction, and the hydrogen adsorption and desorption underpotential deposited peaks are seen in cyclic voltammetry experiments in sulfuric acid solutions. The metallic nature of these films has also been confirmed by electron diffraction analysis. Transmission electron microscopy examination has revealed that the Ir particles are uniform in size, ranging from 1 to 2 nm in diam. These Ir nanoparticles can be converted to hydrous Ir oxide by the normal potential cycling and pulsing route, apparently converting all of the Ir sites to the oxidized form. The resulting Ir oxide films are electrochromic, exhibit high charge densities, and are extremely adherent. Ir oxide films can also be formed directly using the SG route by heating the coated electrodes at temperatures above approximately 500 degrees C. (C) 1999 The Electrochemical Society. S1099-0062(98)11-081-7. All rights reserved.