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 ex cited electrons/holes during photoreaction, new photocatalyst (WOx -TiO2) p owder was prepared by a sol-gel method. The photooxidation efficiency of WO x -TiO2 catalyst was also evaluated by conducting a set of experiments to p hotodegrade methylene blue (MB) in aqueous solution. The photocatalytic act ivity of WO,-TiO2 was examined by X-ray diffraction (XRD), UV-VIS absorptio n spectra, X-ray photoelectron emission spectroscopy (XPS), photoluminescen ce spectra (PL), surface photovoltage spectra (SPS) and electron-field-indu ced surface photovoltage spectra (EFISPS). The experiments demonstrated tha t 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 ex perimental 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 Els evier Science B.V. All rights reserved.