Composite Photocatalysts Containing BiVO₄ for Degradation of Cationic Dyes

The creation of composite structures is a commonly employed approach towards enhanced photocatalytic performance, with one of the key rationales for doing this being to separate photoexcited charges, affording them longer lifetimes in which to react with adsorbed species. Here we examine three composite photocatalysts using either WO₃, TiO₂ or CeO₂ with BiVO₄ for the degradation of model dyes Methylene Blue and Rhodamine B. Each of these materials (WO₃, TiO₂ or CeO₂) has a different band edge energy offset with respect to BiVO₄, allowing for a systematic comparison of these different arrangements. It is seen that while these offsets can afford beneficial charge transfer (CT) processes, they can also result in the deactivation of certain reactions. We also observed the importance of localized dye concentrations, resulting from a strong affinity between it and the surface, in attaining high overall photocatalytic performance, a factor not often acknowledged. It is hoped in the future that these observations will assist in the judicious selection of semiconductors for use as composite photocatalysts.