New Insights into Bi₂WO₆ Properties as a Visible-Light Photocatalyst

Bismuth tungstate has attractive photocatalytic properties under visible light. A better understanding of the origin of that good activity should allow its control and its optimization. An improved photocatalytic activity to different pollutants was obtained using bismuth-based oxide obtained by microwave-assisted synthesis combined with the addition of sodium dodecylsulfate as a size tailoring agent. It is shown using electron paramagnetic resonance that bismuth tungstate is able to generate hydroxyl radicals in aqueous aerated solution, but no superoxide radical anions are formed. The catalytic efficiency relative to TiO₂ could be associated to differences in the number of excitons generated, to their lifetimes as holes and electrons in the semiconductor, and to valence and conduction band positions