W-doped titania nanoparticles for UV and visible-light photocatalytic reactions

Nanocrystalline tungsten doped titanium dioxide powders were prepared by a sol–gel method based on hydrolysis of TiCl4 in aqueous solution. Addition of W was done to extend light absorption of the TiO2-based photocatalysts towards the visible light range. Different tungsten precursors and contents were investigated, regarding their photocatalytic properties and activity. Their photocatalytic activity was measured via degradation of methylene blue (MB) in aqueous solution under ultraviolet (UVA) or visible light. Highest activity was observed for sol–gel samples calcined at 773 K, due to full removal of chloride and increase of crystallite size by thermal treatment. Activity of Ti(W)Ox sol–gel photocatalysts under UVA strongly depends on the tungsten content (maximum reached for a ratio between 1 and 2 mol%) and the precursor choice (WCl6 > (NH4)6H2W12O40 > H2WO4). Under visible-light, activity increases with W content.