Study On Preparation,Modification And Photocatalytic Activity Of Bismuth Tungstate

Bismuth tungstate?Bi₂WO₆?as a new type of photocatalytic material has received more and more attention because of its narrow band gap,high photochemical stability,strong oxidation capacity and low cost advantages.In this paper,we prepared a series of bismuth tungstate and metal modified bismuth tungstate materials by using bismuth nitrate?Bi?NO3?3· 5H2O?and sodium tungstate?Na2WO4 · 2H2O?as raw materials.The effects of different preparation conditions on the activity of the materials and the photocatalytic reaction mechanism were investigated.At last,we provided a theoretical basis for the preparation of photocatalyst with high catalytic activity.The main research contents are as follows:?1?The bismuth tungstate?Bi₂WO₆?was prepared by hydrothermal method,and its best reaction conditions were determined by changing the ratio of raw materials,the pH value of the precursor liquid and the reaction time.The morphology and structure of Bi₂WO₆ were analyzed by X-ray diffraction?XRD?,scanning electron microscopy?SEM?and UV-visible diffuse reflectance spectroscopy?DRS?.The photocatalytic activity of catalysts,to degrade a selected dye such as Rhodamine B?RhB?was studied.The results show that the Bi₂WO₆ nanosheets have the best degree of crystallization and the highest photocatalytic activity when the molar ratio of Bi/W is 2,the precursor pH is 1 and the reaction time is 24 h.?2?The Ag-Bi₂WO₆ was prepared by a two-step method,and the silver ammonia solution was used as the silver source.The degradation of Rhodamine B was studied.The results show that the trace silver content on the surface of bismuth tungstate does not greatly affect the structure and crystal form of bismuth tungstate,but it improves its degradation activity in visible light to a certain extent.The reason for this phenomenon may be that the plasma resonance effect of the silver element increases the absorption range of the catalyst in the visible region,and the silver element as a conductor promotes the separation of photo-generated electron-hole.?3?The Cu-Bi₂WO₆ was synthesized by hydrothermal method using copper nitrate as copper source,and the degradation performance of Rhodamine B at different pH was also explored.The results show that the modification of trace copper has little effect on the crystal form and structure of pure Bi₂WO₆,but it can improve the degradation activity of visible and ultraviolet light.It also shows that the trace copper increases the absorption of catalysts in thevisible area,and promote the photo-generated electron-hole separation efficiency.The main active species in the degradation of Rhodamine B in Bi₂WO₆ was found to be photogenerated holes and hydroxyl radicals.The degradation of Rhodamine B occurred mainly on the surface of the catalyst.Therefore,the adsorption process of Rhodamine B was the important step in the whole degradation.