Electrochemical Properties of TiO₂ Coated ITO Electrodes Prepared by Sol-Gel Method

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An ITO electrode was coated with layers of TiO₂ by using a sol-gel method. The coated electrodes were calcined to change pore and crystal structure of the TiO₂ layer. For these electrodes, cyclic voltammetry and spectro-electrochemical measurements were carried out in the absence of a substrate and in the presence of ethyl viologen as a substrate. Significant differences in electrochemical properties were found between the calcined and uncalcined electrodes. When a negative potential was applied to the uncalcined electrode, Ti³⁺ was formed in its TiO₂ layer. The uncalcined electrode reduced irreversibly ethyl viologen while the calcined one did reversibly. These behaviors are discussed on the basis of the porosity and electronic structure of the TiO₂ layer.