Photocatalytic activity of WO x-TiO 2 under visible light irradiation

Abstract

With an attempt to extend light absorption of the TiO 2-based photocatalysts toward the visible light range and eliminate the rapid recombination of excited electrons/holes during photoreaction, new photocatalyst (WO x -TiO 2) powder was prepared by a sol–gel method. The photooxidation efficiency of WO x -TiO 2 catalyst was also evaluated by conducting a set of experiments to photodegrade methylene blue (MB) in aqueous solution. The photocatalytic activity of WO x -TiO 2 was examined by X-ray diffraction (XRD), UV–VIS absorption spectra, X-ray photoelectron emission spectroscopy (XPS), photoluminescence spectra (PL), surface photovoltage spectra (SPS) and electron-field-induced surface photovoltage spectra (EFISPS). The experiments demonstrated that the MB in aqueous solution was successfully photodegraded using WO x -TiO 2 under visible light irradiation. It was found that an optimal WO x dosage of 3% in WO x -TiO 2 achieved the highest rate of MB photodegradation in this experimental condition. It has been confirmed that WO x -TiO 2 could be excited by visible light ( E<3.2 eV) and the recombination rate of electrons/holes in WO x -TiO 2 declined due to the existence of WO 3 doped in TiO 2. The order of its photoactivity from weak to strong had a good agreement with that of PL intensity and that of EFISPS intensity from strong to weak.