M-BiVO₄ at γ-Bi₂O₃ core-shell p-n heterogeneous nanostructure for enhanced visible-light photocatalytic performance

In this paper, γ-Bi₂O₃, considered as the best photocatalyst among all Bi₂O₃ polymorphs, was successfully prepared on the surface of m-BiVO₄ octahedral crystals through an alkaline "etching" process. Extensive XRD, SEM and TEM characterization revealed the formation of a p-n junction in the form of m-BiVO₄ at γ-Bi₂O₃ core-shell heterostructure. In addition, the alkaline concentration and reaction time during the etching process were studied and found to be critical parameters in the formation and yield of the Bi₂O₃ phase. The visible-light photocatalytic activities of these heterogeneous samples with different γ-Bi₂O₃/m-BiVO₄ phase ratios were evaluated for the degradation of Rhodamine B (RhB). The results indicated that with an optimum amount of γ-Bi₂O₃ on the m-BiVO₄ surface, the powders showed superior photocatalytic performance over pure m-BiVO₄ octahedral crystals. The enhancement mechanisms were discussed based on the specific surface area and γ-Bi ₂O₃ shell thickness, as well as the influences of improved charge carrier transfer on the p-n heterostructure.