Principles of Electrochemistry

Abstract

Electrochromic iridium oxide films have been prepared by the thermal oxidation of iridium-carbon composite films (Ir-C films) obtained by evaporation of Ir from a graphite crucible with an electron gun. The XPS analysis indicates that the Ir-to-C ratio in the Ir-C films lies in a range from 0.061 to 0.165. A change in the transmittance of the Ir-C films begins when they are heated to 225~ or higher. The x-ray diffractometry analysis shows that the thermally oxidized iridium oxide films (TOIROF's) are amorphous when they are heated to temperatures up to 300~ and polycrystalline when heated at a temperature of 350~ The electrochemical measurements show that the degree of electrochromism of the TOIROF's is closely related to those structures. The coloration efficiency of the TOIROF's lies in a range from 13.5 to 15.4 cm2/C at a wavelength of 633 nm. The lifetime test of the TOIROF's has been carried out in 0.5M Na2SO4 electrolyte. Color-bleach cycles of 4 • 105 were recorded without degradation.