WO3/TiO2 composite with morphology change via hydrothermal template-free route as an efficient visible light photocatalyst

The WO3/TiO2 composites are prepared by a template-free synthetic approach based on hydrothermal reaction that leads to the formation of nanoparticles and microspheres with the change in concentrations of ammonium tungstate used as a dopant precursor. 5.0% composite generally exists in loose aggregate nanoparticles. These particles are aggregated to form the peculiar morphology of microspheres at 10.0% WO3/TiO2 due to the in situ formation of ammonium sulfate in supersaturated state. 5.0% composite exhibits the best photoactivity as compared to pure TiO2, P-25 and pure WO3 in the degradation of methyl orange and 2, 4-dichlorophenol in UV and visible light. 10.0% WO3/TiO2 composite contains more dopant contents but exhibits comparable higher activity due to its specific morphology of spheres. Morphological variations of a photocatalyst also influence the photocatalytic efficiencies. Catalysts exhibit high activity owing to the combined effects of both the unique structural characteristics and the tungsten doping. The doped tungsten (W) inhibits the electron-hole recombination rate. The kinetics of the organics degradation is found to follow the Langmuir-Hinshelwood model. (C) 2010 Elsevier B.V. All rights reserved.