Abstract

The most general photocatalyst, TiO_2 and WO_3, are acknowledged to be ineffective in range of visible light. Therefore, many efforts have been directed at improving their activity such as: band-gap narrowing with non-metal element doping and making composites with high specific surface area to effectively separate electrons and holes. In this paper, the method was introduced to prepare a photo-active catalyst to visible irradiation by making a mixture with TiO_2 and WO_3. In the TiO_2-WO_3 composite, WO_3 absorbs visible light creating excited electrons and holes while some of the excited electrons move to TiO_2 and the holes remain in WO_3. This charge separation reduces electron-hole recombination resulting in an enhancement of photocatalytic activity. Added Ag plays the role of electron acceptor, retarding the recombination rate of excited electrons and holes. In making a mixture of TiO_2-WO_3 composite, the mixing route affects the photocatalytic activity. The planetary ball-mill method is more effective than magnetic stirring route, owing to a more effective dispersion of aggregated powders. The volume ratio of TiO_2(4) and WO_3(6) shows the most effective photocatalytic activity in the range of visible light in the view point of effective separation of electrons and holes.

• Keywords: WO_3 powder;TiO_2 powder;visible-light;photocatalysts;Planetary milling;