Low-Temperature Preparation and Photocatalytic Performance of F-Doped Nanosized TiO2 Thin Film

F-doped TiO2 (FTO) sol was prepared using NH4F as the fluorine precursor by a hydrothermal method. FTO thin film was then prepared via dip-coating. The TiO2 thin film prepared from the TiO2 sol that was hydrothermally treated at 120 degrees C for 10 h had preferable transparence and high photocatalytic activity. F doping did not significantly change the grain size of TiO2 but greatly enhanced the photocatalytic activity of the TiO2 film. The optimal doping concentration of F corresponded to F/Ti molar ratio of 0.01. The photocatalytic activity of the FTO thin film was 23% higher than that of TiO2 thin film. X-ray photoelectron spectroscopy results showed that there were two forms of F element in the FTO thin film: surface chemically adsorbed F and substituent lattice F. Both surface adsorbed F and substituent lattice F played a role in the photocatalytic activity enhancement of the FTO thin film.