TiO2, TiO2-1at.% W and TiO2-1at.% Cr were produced from metal-organic precursors by flame spray synthesis (FSS). TiO2-0.5at.% N was obtained by ammonolysis of FSS made TiO2 nanopowder in a rotating tube furnace under NH3 atmosphere. According to the X-ray diffraction (XRD) analysis, anatase is the predominant phase in all samples. Diffusive reflectance and the resulting band gap energy (Eg) were determined by diffusive reflection spectroscopy (DRS).
Additional impurity bands at 2.43 and 2.57 eV for N- and Cr-doped TiO2, respectively have been observed. The impurity band formed in the band gap resulted in increase of the light absorption in the visible range. The photocatalytic performance of the nanopowders under ultraviolet (UV, 290-410 nm) and visible light irradiation (Vis, 400-500 nm) was studied by the degradation of methylene blue (MB) in aqueous suspensions. It was found that all types of dopants influence the structure, interaction with the visible light as well as photocatalytic activity. Among all nanopowders, TiO2-W exhibited the best photoactivity, much higher than the commercial TiO2-P25 nanopowder. The optimum of the photodecolourization was obtained for 0.7 and 1 at.% W.