Experimental and theoretical studies of Fe-doped TiO2 films prepared by peroxo sol–gel method

Transparent, uniform, crack-free and visible light activated Fe-doped TiO2 thin films have been prepared by an organic-free approach using titanium tetrachloride (TiCl4), Fe3+ and ammonium hydroxide solutions to form yellow aqueous peroxo titanic acid (PTA) solution. Pure glass was made superhydrophilic after heating at 550 °C for 1 h and was used as the coating substrate. The PTA solution dispersed uniformly on the superhydrophilic glass by forming a thin film, resulting in a crack-free Fe-doped TiO2 film as observed under FESEM. XRD results confirmed the presence of only anatase phase for all samples after calcination at 550 °C. The Fe-doped TiO2 films exhibited slight red-shift in absorbance and enhanced absorbance in the visible-light region compared with undoped TiO2, attributed to bandgap narrowing by successful Fe3+ doping into TiO2, which is supported by DOS calculations. Photodegradation of stearic acid (SA) revealed that Fe3+ doping increased visible light photocatalytic activity four-fold compared to undoped TiO2 at optimal Fe-doped TiO2 (1 wt% Fe3+) film. At higher Fe ions concentrations, the existence of increased charge recombination sites and segregated iron oxide phase suppressed the photoactivity.