Electrochemical characterization of sol-gel formed Ir metal nanoparticles

Electrochemical studies of a sol-gel (SG) derived Ir-containing film have s hown conclusively that films formed by air drying or heating at temperature s below ca. 500 degrees C are metallic in nature, exhibiting the typical si gnature of Ir metal. Both compact oxide formation and reduction, and the hy drogen adsorption and desorption underpotential deposited peaks are seen in cyclic voltammetry experiments in sulfuric acid solutions. The metallic na ture of these films has also been confirmed by electron diffraction analysi s. Transmission electron microscopy examination has revealed that the Ir pa rticles are uniform in size, ranging from 1 to 2 nm in diam. These Ir nanop articles can be converted to hydrous Ir oxide by the normal potential cycli ng and pulsing route, apparently converting all of the Ir sites to the oxid ized form. The resulting Ir oxide films are electrochromic, exhibit high ch arge densities, and are extremely adherent. Ir oxide films can also be form ed directly using the SG route by heating the coated electrodes at temperat ures above approximately 500 degrees C. (C) 1999 The Electrochemical Societ y. S1099-0062(98)11-081-7. All rights reserved.