Photocatalytic activity of binary and ternary SnO<inf>2</inf>-ZnO-ZnWO<inf>4</inf> nanocomposites

Binary and ternary SnO<inf>2</inf>-ZnO-ZnWO<inf>4</inf> nanocomposites were prepared by a sol-gel route. The photocatalytic activity of the samples was evaluated through the decomposition of 4-nitrophenol and partial oxidation of 4-methoxybenzyl alcohol to p-anisaldehyde. All the mixed catalysts revealed higher photoactivity than bare ZnO, SnO<inf>2</inf> or ZnWO<inf>4</inf> and the best performances were exhibited by the binary nanocomposites. The high photocatalytic activity was explained by the presence of heterojunctions among different semiconductors that enhance the separation of the photogenerated electron-hole pairs, hindering their recombination. As a general consideration, an essential role was played by the electronic features of the samples in the degradation reactions whereas the surface properties were key factors for the selective formation of p-anisaldehyde.