Photocatalytic activity of Li+–Rb+–Y3+ doped or codoped TiO2 under sunlight irradiation

Doped TiO2 particles were synthesized by solid grinding and sol–gel methods. The ensuing powders were analysed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and ground state diffuse reflectance absorption spectroscopy (GSDR). The doped samples prepared by solid grinding at 400 °C were in the anatase form, while those synthesised via sol–gel method and calcinated at the same temperature were dominated by the rutile phase. The X-ray photoelectron spectroscopy (XPS) revealed a surface segregation of the doping elements namely for Y, Rb and Rb–Y. The photocatalytic activity of the prepared catalysts, under sunlight irradiation, was evaluated using 2-naphthol as a pollutant model. Results showed a great enhancement in the photocatalytic efficiency with incorporation of Y in samples prepared by solid grinding, while in samples prepared via sol–gel process both Rb and Y dopants greatly improve the photocatalytic activity. The Langmuir–Hinshelwood model was used to describe the photocatalytic reactions from which a pseudo-first-order kinetics was established. The repeatability of photocatalytic activity was also tested for several degradation cycles.