Mesoporous films of TiO2 as efficient photocatalysts for the purification of water

Variably thick mesoporous TiO2 films were prepared by alternately dip-and spray-coating using sol containing titanium(IV) alkoxide, concentrated HCl and suitable block-copolymer as a structure directing agent. The film thickness was controlled by varying the number of deposited layers. Their porosity was homogeneous: surface area and pore volume increased linearly with increasing number of deposited layers. Photoactivity of the films was tested employing photocatalytic degradation of 10(-4) M 4-chlorophenol in a 60 mL photoreactor under UV irradiation at 365 nm. The incident light intensity was 1 mW cm(-2). The degradation rate constants increased with increasing number of layers, proportional to their absorbances. However, the progressive improvement of the photocatalytic performance slightly decreased with the increasing number of layers. The spray-coating layers exhibited lower photocatalytic performance due to their smaller thicknesses.