Photocatalytic activity of WOx-TiO2 under visible light irradiation

With an attempt to extend light absorption of the TiO2-based photocatalysts toward the visible light range and eliminate the rapid recombination of excited electrons/holes during photoreaction, new photocatalyst (WOx -TiO2) powder was prepared by a sol-gel method. The photooxidation efficiency of WOx -TiO2 catalyst was also evaluated by conducting a set of experiments to photodegrade methylene blue (MB) in aqueous solution. The photocatalytic activity of WO,-TiO2 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 WOx-TiO2 under visible light irradiation. It was found that an optimal WO, dosage of 3% in WOx-TiO2 achieved the highest rate of MB photodegradation in this experimental condition. It has been confirmed that WOx-TiO2 could be excited by visible light (E < 3.2 eV) and the recombination rare of electrons/holes in WOx-TiO2 declined due to the existence of WO3 doped in TiO2. 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. (C) 2001 Elsevier Science B.V. All rights reserved.