One step activation of WOx/TiO2 nanocomposites with enhanced photocatalytic activity

New photocatalyst (WOx–TiO2) powder was successfully prepared by a sol–gel method with an attempt to extend light absorption of the TiO2-based photocatalyst towards the visible light range and eliminate the rapid recombination of excited electrons/holes during photoreaction. The photo composite was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), BET, Raman spectra, UV–vis diffuse reflectance spectra (DRS), photoluminescence spectra (PLS) and X-ray photoelectron spectroscopy (XPS). XRD, Raman, HRTEM and XPS analysis indicated that WOx is uniformly dispersed on the surface of TiO2 probably with monolayer thickness and the mean particle size of the composite was 12 nm. XPS analysis also indicated that the vacuum activated composites contained more W in reduced form while the calcined composites showed more W in hexavalent form. The beneficial effect of W can be explained by considering the formation of W+5 species by means of a transfer of photo-generated electrons from TiO2 to W+6.Subsequently W+5 could be oxidized to W+6 by transferring electrons to adsorbed O2.DRS showed an extension of light absorption into the visible region for this WOx composite and PL analysis indicated that the electron-hole recombination rate has been effectively inhibited when WOx is deposited on the surface of TiO2.The samples activated in vacuum showed higher photocatalytic activity than calcined samples in case of MO and superior activity in case of phenol. The optimal WO3 dosage of 4.0% in WOx–TiO2 achieved the highest rate of photodegradation in this experimental condition.