Solar photocatalytic activities of porous Nb-doped TiO₂ microspheres by coupling with tungsten oxide

Highlights: • Nb-TiO₂/WO₃ was prepared by USP method combined impregnation method. • Nb-doping extend the spectral absorption of TiO₂ into visible spectrum. • Nb-TiO₂/WO₃ has a similar optical band gap as Nb-TiO₂. • PL spectra indicate WO₃ can accept the photoexcited electrons from Nb-TiO₂. • Nb-TiO₂/WO₃ shows higher activity than TiO₂ and Nb-TiO₂ under solar light. - Abstract: Nb doped TiO₂ microspheres modified with WO₃ (Nb-TiO₂/WO₃) was prepared by ultrasonic spray pyrolysis method combined with impregnation method. The microspheres were characterized with SEM, TEM, XRD, BET, photoluminescence and UV–vis absorption spectra. The Nb-doping was observed to extend the spectral absorption of TiO₂ into visible spectrum, and the absorption onset was red-shifted for about 88 nm compared to pristine TiO₂ microspheres. Nb-TiO₂/WO₃ microspheres do not display a red-shifted absorption edge compared with Nb doped TiO₂ microspheres. Under solar irradiation, Nb-TiO₂/WO₃ microspheres showed higher photocatalytic activity for methylene blue degradation compared with that of pure TiO₂ microspheres and Nb doped TiO₂ microspheres, which could be ascribed to the extended light absorption range and the suppression of electron-hole pair recombination