Synthesis, Surface Acidity and Photocatalytic Activity of WO<sub>3</sub>/TiO<sub>2 </sub>Nanocomposites – An Overview

Titania has been studied to be one of the best photocatalysts for the decomposition of many organic pollutants present in aqueous medium. Because of the wide band gap energy of TiO 2 (3.2 eV) it can be activated only under UV light region which is present 4 % in the solar light spectrum. The photocatalytic activity of TiO 2 was enhanced by means of several methods. TiO 2 coupled with other semiconductor has gained additional importance, owing to improving the efficient charge separation by trapping the photogenerated electrons. WO 3 is a better semiconductor having relatively lower band gap energy (2.8 eV) and absorb broad solar light spectrum. The formation of WO x monolayer on TiO 2 notably increases the surface acidity of TiO 2 . This increasing the surface acidity of WO 3 /TiO 2 photocatalyst facilitates the adsorption of the more hydroxyl group in addition to more organic reactants on its surface which obviously facilitate the enhancement of photocatalytic activity. In this review, the synthesis methods and photocatalytic activity of some selected and unique results related to WO 3 /TiO 2 photocatalyst were discussed. The efficient charge separation, increased absorption of the reactants by increasing the surface acidity and high aspect ratio structures of WO 3 /TiO 2 are also reviewed.