Microstructures and photocatalytic properties of Ag+ and La3+ surface codoped TiO2 films prepared by sol–gel method

Ag+ and La3+ surface codoped TiO2 films were successfully prepared by the improved sol–gel and doping processes. The as-prepared specimens were characterized using differential thermal analysis-thermogravimetry (DTA–TG), X-ray diffraction (XRD), high-resolution field emission scanning electron microscopy (FE-SEM), X-ray energy dispersive spectroscopy (EDS), Brunauer–Emmett–Teller (BET) surface area, Photoluminescence spectrum (PL) and UV–vis diffuse reflectance spectroscopy. The photocatalytic activities of the films were evaluated by degradation of an organic dye in aqueous solution. The results of XRD, FE-SEM and BET analyses indicated that the TiO2 films were composed of nano-particles or aggregates with a size of less than 10 nm. With the codoping of Ag+ and La3+, TiO2 films with high photocatalytic activity and clearly responsive to the visible light were obtained. The improvement mechanism by ions doping was also discussed.

Graphical AbstractThe PL intensity of Ag+ and La3+ surface codoped TiO2 was the lowest among all samples, indicating the recombination of electron and hole was effectively prohibited compared with pure TiO2, Ag+ and La3+ bulk codoped TiO2.Figure optionsDownload as PowerPoint slideHighlights
► Ag+ and La3+ codoping can reduce the crystal size of TiO2.
► Ag+ and La3+ surface codoped TiO2 films have an obvious optical response red-shift.
► Ag+ and La3+ surface codoped TiO2 films can exhibit excellent photocatalytic activity under both UV and visible light irradiations.