Pulsed photoelectrochemistry of titanium dioxide

Abstract

Photocurrent transients induced by pulsed-laser illumination of polycrystalline titanium dioxide electrodes in contact with aqueous electrolytes have been investigated in the micro- and milli-second time ranges. Reduced pyrolysed, and anodized, electrodes gave anodic photocurrents as expected, but unreduced pyrolysed electrodes gave anodic currents at low laser fluences and both anodic and cathodic photocurrents at higher fluences, owing to saturation of the depletion layer: the quantum yields decreased sharply with increasing fluence. The electrodes under pulsed illumination are models for colloidal and particulate TiO₂, widely investigated as elements for the photoelectrochemical conversion and stroage of solar energy, under weak continuous illumination: the results show why, under appropriate conditions of doping level and irradiance, both oxidation and reduction are expected to take place at the semiconductor surface, as has been observed chemically.