SELECTIVE SYNTHESIS AND VISIBLE LIGHT PHOTOCATALYTIC ACTIVITIES OF BiVO4 WITH DIFFERENT CRYSTALLINE PHASES

摘要

Bismuth vanadate (BiVO4) is one of the non-titania-based visible light-driven semiconductor photocatalysts. It is a promising material for a wide variety of applications; for example, it is usually used as gas sensors, posistors, solid state electrolytes positive electrode materials for lithium rechargeable batteries, etc. In addition, it also shows catalytic and photocatalytic properties and it is commonly used as a catalyst in water splitting and oxidative dehydrogenation. However, the photophysical and photocatalytic properties of BiVO4 are strongly influenced by its crystal form. There are three crystalline phases reported for synthetic BiVO4: zircon structure with tetragonal system (z-t), scheelite structure with monoclinic (s-m) and tetragonal (s-t) systems. When BiVO4 (z-t) is heat-treated at about 400-600 °C, BiVO4 (s-m) can be obtained. And the phase transition between BiVO4 (s-m) and BiVO4 (s-t) is reversible at about 255 °C. The BiVO4 (s-m) powder showed high activity for photocatalytic O2 evolution under visible light irradiation while the photocatalytic activity of BiVO4 (z-t) was negligible. So, the photocatalytic properties of BiVO4 (s-m) were quite different from those of BiVO4 (z-t) for O2 evolution. BiVO4 can be synthesized by different methods. Generally, monoclinic BiVO4 is obtained by the high-temperature process, whereas tetragonal BiVO4 is prepared in aqueous media by the low-temperature process. BiVO4 with different crystal forms can be obtained from the different preparation methods. It is of great importance to control the crystal form of BiVO4 in a simple approach.