Hydrothermal synthesis of m-BiVO4/t-BiVO4 heterostructure for organic pollutants degradation: Insight into the photocatalytic mechanism of exposed facets from crystalline phase controlling.

A series of BiVO4 photocatalysts were prepared by a co-precipitation followed hydrothermal synthesis method for the photodegradation of Rhodamine B (RhB) and 2,4-Dichlorophenol (2,4-DCP). The crystalline phase ratio of the heterostructured BiVO4 (m-BiVO4/t-BiVO4) between monoclinic and tetragonal could be easily controlled at different pH and hydrothermal time. Interestingly, the as-prepared heterostructured BiVO4 photocatalyst at pH = 7 for 24 h (BiVO4-7-24) showed the highest photocatalytic activities for the degradation of RhB, while the best photodegradation of 2,4-DCP was obtained at pH = 0.5 for 24 h (BiVO4-0.5-24). The photocatalytic mechanism can be explained by the different charge carrier transfer pathways and active oxidation species in the m-BiVO4/t-BiVO4 heterostructure. More importantly, the exposed facets originated from crystalline phase controlling in BiVO4-0.5-24 and BiVO4-7-24 photocatalyst is an essential reason for the different photocatalytic activity. The proposed energy band alignments of BiVO4-0.5-24 and BiVO4-7-24 photocatalyst provide insights into the photocatalytic mechanism of the m-BiVO4/t-BiVO4 heterostructure.