Improved Photocatalytic Performance of Heterojunction by Controlling the Contact Facet: High Electron Transfer Capacity between TiO2 and the {110} Facet of BiVO4 Caused by Suitable Energy Band Alignment

Charge separation at the interface of heterojunctions is affected by the energy band alignments of the materials that compose the heterojunctions. Controlling the contact crystal facets can lead to different energy band alignments owing to the varied electronic structures of the different crystal facets. Therefore, BiVO4-TiO2 heterojunctions are designed with different BiVO4 crystal facets at the interface ({110} facet or {010} facet), named BiVO4-110-TiO2 and BiVO4-010-TiO2, respectively, to achieve high photocatalytic performance. Higher photocurrent density and lower photoluminescence intensity are observed with the BiVO4-110-TiO2 heterojunction than those of the BiVO4-010-TiO2 heterojunction, which confirms that the former possesses higher charge carrier separation capacity than the latter. The photocatalytic degradation results of both Rhodamine B and 4-nonylphenol demonstrate that better photocatalytic performance is achieved on the BiVO4-110-TiO2 heterojunction than the BiVO4-010-TiO2 heterojunction under visible light (422 nm) irradiation. The higher electron transfer capacity and better photocatalytic performance of the BiVO4-110-TiO2 heterojunction are attributed to the more fluent electron transfer from the {110} facet of BiVO4 to TiO2 caused by the smaller interfacial energy barrier. This is further confirmed by the selective deposition of Pt on the TiO2 surface as well as the longer lifetime of Bi5+ in the BiVO4-110-TiO2 heterojunction.