Cu_2O nanoparticles decorated BiVO_4 as an effective visible-light-driven p-n heterojunction photocatalyst for methylene blue degradation

摘要

Bismuth vanadate (BiVO_4) is a chemically stable and nontoxic semiconductor (SC) photocatalyst that can absorb visible light to degrade most of pollutants in aqueous solution due to suitable band-gap energy (ca. 2.4 eV), but it usually shows a low activity in its pristine form owing to poor charge-separation characteristics and the weak surface adsorption properties. In this paper, we demonstrated that the photocatalytic activity of BiVO_4 can be greatly enhanced by surface modification with Cu_2O nanoparticles through polyol reduction method. The modified photocatalysts (Cu_2O/BiVO_4) with proper loading amount of Cu_2O (0.75 wt%) showed the highest photocatalytic degradation activity for methylene blue (MB) degradation with the pseudo-first-order rate constant k_(app) and degradation efficiency two times higher than pristine BiVO_4 under visible light and solar light irradiation. The characterizations of resulting photocatalysts revealed that decoration of Cu_2O nanoparticles led to the formation of a p-n heterojunction at the contact interface of Cu_2O and BiVO_4, which narrowed the band gap of BiVO_4 for extending the absorption range of visible light and promoted the charge transfer across interface for suppressing the recombination of photogenerated electron-hole pairs, thus improving the catalytic performance of photocatalysts. This work demonstrates that the structural integration of p-type Cu_2O SC with n-type BiVO_4 SC will be a new promising strategy to develop a high-efficient heterojunction photocatalyst for visible-light-driven degradation of pollutants.