Effect of substrate on surface morphology and photocatalysis of large-scale TiO2 films

Nanostructured TiO2 films were prepared on a variety of substrates, including acid frosted soda-lime glass, acid frosted soda-lime glass pre-coated with a SiO2 barrier layer, commercial glazed ceramic tile and 6061 aluminum alloy. For each substrate, the phase and microstructure of the films were determined to be exclusively anatase. However, the growth of the TiO2 crystallites, the film morphology and thickness varied substantially with substrate. Thermal stress, resulting from the difference in the coefficient of thermal expansion between the substrates and the films, contributed to the formation and propagation of cracks. This was most clearly observed on the films deposited on SiO2 barrier layer and aluminum. The photocatalytic activity of the TiO2 films deposited on glass with and without SiO2 barrier layer, ceramic, and aluminum was studied via UV decolorization of methyl orange in aqueous solution. Complete degradation rapidly occurred on the TiO2/glass and TiO2/SiO2 barrier layer films, but not with the ceramic or metal substrates. It appears that the photocatalytic activity of the films deposited on aluminum and ceramic substrates was affected by the quantity and the size of the anatase crystallites. The aluminum substrate promoted the formation of TiO2 films with the largest anatase crystallite size, exhibiting a cracked morphology, where as the ceramic substrate resulted in the formation of TiO2 films with large crystallite size in an island morphology