Synthesis And Photocatalytic Activity Of BiVO₄ Under Visible-light Irradiation

Bismuth vanadate(BiVO₄) is an visible-light driven semiconductor photocatalyst.It exists in three main crystal structures:monoclinic scheelite,tetragonal zircon and tetragonal scheelite. The photocatalytic property of BiVO₄ is strongly influenced by its crystal structure.Monoclinic BiVO₄ showed high photocatalytic activity while the photocatalytic activity of tetragonal BiVO₄ was negligible.Therefore,many efforts have been made to obtain monoclinic BiVO₄.In this paper,BiVO₄ powders were obtained by hydrothermal method and solid-state reaction at low temperature.An additive-free hydrothermal process was involved to synthesis visible-light driven BiVO₄ from aqueous Bi(NO₃)₃ and NH₄VO₃ solutions.The characterization of the as-prepared BiVO₄ samples was carried out by XRD,SEM,nitrogen adsorption and UV-vis DRS.It can be infered that the pH value plays an important role in the selective synthesis of BiVO₄,there exsits an optimal pH value range(2＜pH＜7) for the preparation of monoclinic BiVO₄.It can affect the morphology of resulting products significantly as well.When all samples were applied to the photodegradation of MB under visible light,the monoclinic BiVO₄ showed an obvious superiority when compared to the tetragonal BiVO₄,it showed better photocatalytic property than TiO₂(P25).KBrO₃ can improvement the photocatalytic activity of BiVO₄ when it was used as electron acceptor.The synthesis by solid-state reaction at low temperature can avoid the use of HNO₃,which was used in almost all the wet chemical methods,and the reaction temperature was below 120℃, the synthesis route was simple and convenient.Thus,solid-state reaction at low temperature is a green chemical synthesis method for the preparation of BiVO₄.Urea was an important imfactor in selective preparation of monoclinic and tetragonal BiVO₄.The as-prepared monoclinic BiVO₄ samples possess better coloristic properties than tetragonal counterparts.