Low-temperature synthesis and characterization of TiO2 and TiO2–ZrO2 photocatalytically active thin films

Abstract

Transparent TiO₂ and TiO₂–ZrO₂ (molar ratio Zr/Ti = 0.1) thin films were produced by low-temperature sol–gel processing from nanocrystalline aqueous based solutions. The structural features and compositions of the films treated at room temperature, 100 °C and 500 °C were investigated by X-ray diffraction, X-ray photoelectron spectroscopy and thermal analysis. Addition of zirconia increased specific surface area (140–230 m² g⁻¹) and hindered the growth of anatase crystallites, exhibiting a constant size of 6–7 nm in the whole temperature range. These significant changes with respect to pure TiO₂ in anatase crystalline form did not result in significantly and systematically different photocatalytic activity, which was evaluated in terms of aqueous pollutant degradation (azo-dye in water) and self-cleaning ability (fatty contaminant deposit). The films treated at only 100 °C showed excellent photocatalytic activity towards azo-dye degradation. Contact angle measurements of aged and contaminated surfaces revealed a fast or sharp hydrophilicity gain under UVA illumination. Accordingly, the results of this study confirmed the potential application of advantageous low-temperature films in water treatment as well as for self-cleaning surfaces.