Geopolymer-supported photocatalytic TiO2 film: Preparation and characterization

The article reports preparation and characteristics of TiO2 films deposited on geopolymer substrates via sol-gel dip coating process. Serious cracking takes place within TiO2 film derived from sol precursor with butyl titanate as titanium source and prepared by traditional dip-coating process on geopolymer substrates. It is found that the incorporation of 6% Polyvinylpyrrolidone, and the application of vacuum impregnation before withdrawing relieve cracking significantly, and the resulting TiO2 film exhibits mesoporous morphology. The TiO2 film annealed at 600 °C is mainly composed of anatase phase, and exhibits highest photocatalytic activity evaluated by degrading methylene blue. Multilayer dip-coating promotes photocatalytic activity of the obtained TiO2 film in some extent, but decreases in photocatalytic efficiency and homogeneity are observed when the number of coating layers is over 3.