Study On The Modification Of Bi₂WO₆ And Its Photocatalytic Degradation Of Toluene

Volatile organic pollutants?VOCs?are recognized as a class of atmospheric pollutants that are toxic and harmful to the human body.After a series of photochemical reactions,smog will form.Therefore,the treatment of VOCs is important aspects of the"defense of the blue sky".Photocatalytic technology has unique advantages and is widely used in the degradation of VOCs.So far,researchers have developed a series of photocatalysts.Bi₂WO₆ is considered as one of the photocatalysts with potential development,but pure Bi₂WO₆ has the following problems in practical applications:it has electron-hole recombination easily;and it has low utilization of visible light.This subject used Bi₂WO₆ as the main catalyst to solve the above problems by controlling the surface morphology,forming heterojunction,and depositing noble metal.The catalysts'activity test is evaluated with toluene which as the target pollutant for photocatalytic degradation.The research content is as follows:?1?Bi₂WO₆ Morphology and Structure Regulation:The effects of polyvinylpyrrolidone?PVP?on the preparation conditions and activity of Bi₂WO₆catalysts were analyzed.The Bi₂WO₆ catalysts were analyzed by a series of characterization techniques,and analysis of its crystal phase structure and morphology.The synthesis of Bi₂WO₆ catalysts was evaluated by photocatalytic degradation of toluene.During the experiment,Bi₂WO₆ were synthesized by hydrothermal method and Solvothermal method with adding PVP.It was determined that the optimal amount of pvp added in the two synthesis methods.The results show that the addition of PVP had a certain effect on improving the morphology of Bi₂WO₆catalyst,which help to expand the absorption range of visible light and improve the photocatalytic degradation performance of toluene.?2?MoS₂and Bi₂WO₆ were combined to form heterojunction,expand the visible light absorption range,and increase electron transmission and separation.MoS₂/Bi₂WO₆ composite catalysts is formed by solvothermal.The influence of the composite catalyst with single factor and different molar ratio of Mo:W on the photocatalytic degradation of toluene was investigated.The structure and optical properties of the composite catalyst were characterized.TEM images show that the Bi₂WO₆ nanoparticles were loaded on the sheet of MoS₂.The toluene degradation experiment found that the activity of MoS₂/Bi₂WO₆ composite catalyst's activity is significantly improved compared to pure Bi₂WO₆.When the molar ratio of Mo:W is1:5,MoS₂/Bi₂WO₆ exhibits the best photocatalytic degradation rate.And the degradation rate reaches 91%at 120.0 min.The increase in degradation rate is mainly caused by two reasons:on the one hand,the addition of MoS₂ can form heterojunctions,which has a positive effect on the electron-hole separation,thereby improving the photocatalytic activity of the material;On the other hand,the addition of MoS₂ improved the absorption of visible light.?3?Bi₂WO₆ was modified with Bi metal.The plasmon resonance effect on the surface of Bi metal can effectively accelerate the charge transfer.The Bi/Bi₂WO₆ was synthesized by a simple two-step hydrothermal/solvothermal route.The structure and optical properties of the synthesized composite catalyst were analyzed by a series of characterization techniques,and the activity of Bi/Bi₂WO₆ composites catalyst was evaluated by degradation the toluene.TEM images showed that Bi metal was successfully loaded on the surface of Bi₂WO₆ nanosheets,and it is clear that there is a contact between the interface of Bi nanosphere and Bi₂WO₆ nanosheet;XPS data shows that the addition of Bi after metal,the binding energy of the Bi 4f and W 4f orbitals of the composite catalyst is shifted to the direction of high binding energy compared to the single Bi₂WO₆ catalyst,which can be attributed to a strong interaction between the Bi₂WO₆ and metallic Bi.Degradation experiments show that when the reduction temperature was controlled at 180.0?,the corresponding Bi/Bi₂WO₆ composite photocatalyst?180.0?sample?has the best photocatalytic degradation ability,and the degradation rate reaches 88%at 150.0 min.Bi/Bi₂WO₆composites photocatalysts have a good photocatalytic degradation ability,indicating that the SPR effect of Bi metal can effectively improve the ability of absorbing visible light and promoting the transfer of charge carriers.?4?In the experiment of toluene degradation by MoS₂/Bi₂WO₆ and Bi/Bi₂WO₆under visible light,with the increase of initial concentration of toluene,the removal efficiency of MoS₂/Bi₂WO₆ and Bi/Bi₂WO₆ composite catalysts decreased.The increase of oxygen concentration promotes the catalytic reaction of the composite catalyst.However,if the oxygen concentration continues to increase to 25%,the degradation rate of toluene for MoS₂/Bi₂WO₆ and Bi/Bi₂WO₆ composite catalysts tends to decrease.Light intensity also plays an important role in the whole reaction system.With the increase of the light intensity,the more photons per unit area of the composite surface,the higher the degradation rate of the material for toluene.