Photocatalytic and photoelectrochemical properties of sol-gel TiO2 films of controlled thickness and porosity

Nonporous and mesoporous TiO2 films of well-defined thicknesses were synthesized by the sol-gel technique with dip-coating as the deposition method. Due to the potential applications as self-cleaning surfaces and photoanodes in water splitting activities of the prepared TiO2 films were evaluated for the photodegradation of model ink 2,6-dichloroindophenol and water photooxidation in aqueous media containing an inorganic salt. Thickness and mass parameters of the TiO2 films depend linearly on the number of deposition cycles (dip-coating, drying and calcinations). Due to different viscosities of the precursor, thicknesses of a single layer of nonporous and mesoporous titania film were 65 nm and 300 nm, respectively. The crucial effect of film mass on the decolourization of solid organic films was confirmed. Photocurrent in aqueous electrolyte depends strongly on the type of conductive substrate. It is about five times lower for indium doped tin oxide (ITO) which was confirmed to be due to the increase of resistivity of ITO conductive layer during calcinations. Mesoporous films reveal significantly lower photocurrents than nonporous films which can be explained by insufficient charge transfer in mesoporous films consisting of very small mesopores. (C) 2014 Elsevier B.V. All rights reserved.