Preparation And Photocatalytic Performance Of Bismuth Tungstate Composites

In recent years,photocatalysis technology has been widely concerned by people.The main advantages of photocatalysis lie in mild reaction conditions,no secondary pollution,inexhaustible use of the sun,and cheap and non-toxic catalyst can be used repeatedly.The most representative photocatalyst is Ti O₂catalyst,which can be used for air purification and sewage treatment and has the function of sterilization.However,Ti O₂has a wide band gap and a small absorption range of light.Therefore,it is an inevitable trend of photocatalytic development to find photocatalysts with excellent performance to achieve efficient utilization of energy.Bismuth tungstate（Bi₂WO₆）is a photocatalyst with visible light response.Compared with traditional photocatalyst,Bi₂WO₆ has larger specific surface area and smaller band gap,so it has a higher utilization rate of light energy.Moreover,the quantum efficiency and catalytic activity of Bi₂WO₆ can be further improved by means of ion doping.The research contents of this paper are as follows:（1）Bi₂WO₆ visible light catalyst was successfully synthesized from bismuth nitrate pentahydrate（Bi（NO₃）₃·5H₂O）and sodium tungstate dihydrate（Na₂WO₄·2H₂O）by hydrothermal synthesis.The effects of different conditions（reaction temperature,reaction time,p H value of adjusting precursor night）on the structure,morphology and photocatalytic performance of the synthesized products were investigated,and the best reaction conditions were determined.The photocatalytic performance of bismuth tungstate was determined by measuring the degradation rate of rhodamine B（Rh B）in simulated industrial dye wastewater.The results show that when the hydrothermal temperature is 160℃,the hydrothermal time is24h,the p H is 4,the photocatalytic activity is the best,and the degradation rate can reach 91.7%.（2）Bi₂WO₆ matrix catalyst was prepared by hydrothermal method.Ag modified Bi₂WO₆ catalyst was prepared by two-step hydrothermal method.The effects of different amount of Ag on the crystal structure and properties of the synthesized samples were studied.The results show that the modification of Ag does not change the morphology of Bi₂WO₆,but extends the visible light absorption range of Bi₂WO₆,and the photocatalytic activity of the obtained sample Ag/Bi₂WO₆ is higher than that of pure Bi₂WO₆.Among them,5%Ag/Bi₂WO₆（w）sample has the best catalytic activity,and the photocatalytic degradation rate of oxytetracycline solution is 83%after two hours of illumination,compared with that of pure bismuth tungstate,the photocatalytic degradation rate of oxytetracycline solution is only 54%,which shows good performance in the cycle test,providing a new perspective for the development of new visible light photocatalyst.（3）Bi₂WO₆ photocatalyst with different Ce doping amount was prepared by one-pot hydrothermal synthesis method,and its photocatalytic activity was investigated by degradation of oxytetracycline solution.The experimental results show that the doping of Ce element has an important effect on the structure and properties of the samples.Ce³⁺infiltrates into the structure of Bi₂WO₆ to replace Bi³⁺,causing crystal distortion of Bi₂WO₆ and greatly reducing the recombination rate of photoinduced electrons and holes,which effectively improves the photocatalytic performance of Bi₂WO₆.When the doping amount is 6%(n Ce³⁺:n Bi₂WO₆),the sample showed many unique photoelectric and physicochemical properties.After two hours of visible light irradiation,the degradation effect of oxyterracycin solution was the best,the degradation efficiency reached 88.11%,compared with pure Bi₂WO₆,the degradation rate increased by 35%,and had good stability.