The pH Response Drift of Thermally Grown Titanium Oxide Thin Films

Abstract

The pH-response drift of thermally grown oxide film on titanium electrode was investigated through Devanathen hydrogen permeation tests and open-circuit potential measurements. Thermostatic measurements using heat-treated titanium electrodes were conducted in solutions with pH being changed stepwise from pH 4 to pH 10. A numerical simulation of the pH-response drift based on a diffusion-controlled model was made using experimental values of hydrogen diffusion coefficient and oxide film concentrations as parameters. Results of the study showed that there was a relative lower pH-response drift in titanium electrodes heat-treated at 400-700°C for 10 min. Combined Auger electron spectroscopy and scanning electron microscopy ͑SEM͒ revealed the formation of a dense oxygen-rich film on these titanium electrodes. The retardation effect of this film is believed to be responsible for the low pH-response drift in such heat-treated electrodes.

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