EFFECT OF ANIONS ON THE ELECTROREFLECTANCE SPECTRA OF ANODICALLY OXIDIZED IRIDIUM IN AQUEOUS-SOLUTIONS

The spectra intensity of the imaginary part of electroreflectance for hydrated IrO2 films on Ir electrodes in alkaline solutions increases u pon adding anions of perchlorate, sulfate, and phosphate, as the energ y of formation of the hydrogen bond between the anion and water increa ses. In the case of perchlorate and sulfate ions in acid solutions, th is phenomenon is complicated by the involvement of free water as an ac ceptor of protons from adsorbed water molecules. No simple dependence can describe the influence of the anion nature on the spectra of the r eal part of electroreflectance because of the spectrum sign inversion. The electroreflectance caused by electromodulation of the optical pol arizability of the water adsorption layer is believed to determine the rate of electrochromic transition in the IrO2 films in aqueous soluti ons.