Study On Preparation Of TiO₂ Photocatalytic Thin Films Via Non-hydrolytic Sol-gel

TiO₂ film with high photocatalysis was prepared by nonhydrolytic sol-gel methodusing TiCl₄ as precursor, absolute ethanol as oxygen donor and PEG as additive.Systematic studies were made on the influences of TiCl₄ concentration, PEG molecularweight and its contents, the oxygen donors and coating times on the structures andphotocatalysis of the films by means of XRD, FTIR, FE-SEM and UV-VIS. The reactionmechanism, microstructures and photocatalysis of TiO₂ film by hydrolytic andnon-hydrolytic sol-gel routes were compared. On the basis of optimizing processingparameters, futher reasearch was made on the effects of Si⁴⁺ and Al³⁺ doping on thestructure and photocatalysis of TiO₂ films.TiO₂ photocatalytic film has been fabricated via nonhydrolytic sol-gel route which ischaracterized by simple operation and low cost. The optimizing processing parameters isthat TiCl₄ concentration is 0.83mol/L, PEG molecular weight is 1000 and its molar ratioto TiCl₄ is 0.10, and the optimal coating numbers is 5 times. The TiO₂ film, with freecrystal grains and a great deal of evenly-dispersed micropores, has the lagerest specificaera, and consequently the best photocatalytisis. The methyl orange photodegradationratio can reach above 79ï¼…after irradiated for 8 hours under ultraviolet light.The non-hydrolyric sol-gel method has different reaction mechanism from thehydrolytic one. The non-hydrolytic route involves the cleavage of the carbon-oxygenbond instead of the metal-oxygen bond. The phase transition temperature ofanatase-to-rutile by non-hydrolytic sol-gel is 750℃, which is higher than that bytraditional hydrolytic sol-gel method. TiO₂ films by non-hydrolytic sol-gel, with finergrain and higher specific surface aera, have higher photocatalytisis than that oftraditional hydrolytic sol-gel method.When Si⁴⁺ and Al³⁺ were doped into TiO₂ thin films, they not only retard thetransformation of anatase to rutile, but also suppress the growth of TiO₂ particles. Thecompound doping of Si⁴⁺ and Al³⁺ is more effective than single Si⁴⁺ doping. 15ï¼…Si⁴⁺ and5ï¼…Al³⁺ compound doping causes the transformation temperature of anatase to rutileincreases from 750℃to 1200℃. Compared to pure TiO₂, 20ï¼…Si⁴⁺ doped TiO₂ has bestphotocatalytisis, its degradation rate increases by 40ï¼…after heated at 1000℃.