The Preparation Of Bi₂MoO₆ Photocatalyst In Different Dimensions And Its Application For Photoreduction Of CO₂

Over-utilization of fossil fuels not only causes global energy crisis,produces a large amount of greenhouse gas CO₂,but also causes environmental problems such as global warming and sea level rise.In order to solve the two major crises at the same time,photo catalytic reduction of CO₂ to produce organic fuels has become the most potential research topic.In recent years,bismuth-based semiconductors have drawn attention due to their high efficiency of visible light absorption.Therefore,this project mainly researches the application of Bi₂MoO₆ material in the direction of photocatalytic reduction of CO₂ to produce hydrocarbons.In this thesis,a hydrothermal method for preparing Bi₂MoO₆ quantum dots loading on reduced graphene oxide（RGO）has been developed.Due to the small particle size of Bi₂MoO₆ quantum dots,the migration distance of photo-generated carriers is reduced from the internal to the surface,so that the migration time is shortened,the photo-carrier recombination rate is greatly reduced.While the recombination of Bi₂MoO₆ and RGO,the absorption of visible light is enhangced.At the same time,the photo-generated carriers of the quantum dot on the surface are transmitted to the RGO layer material in time under visible light excitation,further preventing recombination of electron-hole pairs.By comparing the photocatalytic reduction performance of Bi₂MoO₆/GO composites with different additions of GO,it was found that when the addition amount of GO at 10 mg,the yield of methanol and ethanol reached the highest after reacting for4h at visible light,which were 84.8μmol gcatal.^-1and 57.5μmol gcatal.^-1,respectively.The total yield was 142.3μmol gcatal.^-1,which was 2.22 times higher than the pure Bi₂MoO₆ quantum dots(64.0μmol gcatal.^-1).In addition,a method of solvothermal preparing ultrathin monolayer Bi₂MoO₆nanosheets self-assembled into 3D hydrangeas has also been developed.This kind of material not only possesses the advantages of the ultrathin monolayer nanostructures which can shortens the diffusion time of carrier transport from the inside to the surface and effectively prevents the recombination of carriers,but also has the advantages of preventing stacking of layered materials,large specific surface area,more contact with reactants,more active sites and so on.Through the single variable method to explore the effect of surfactant CTAB,solvent ethylene glycol and solvent heat time on the morphology and properties of the material,it was confirmed that both CTAB and solvent ethylene glycol have a direct effect on the configuration of 3D Bi₂MoO₆hydrangea material.The time of solvothermal affects the thickness of the nanosheet.When the time of solvothermal is 3h,the nanosheet crystallizes well,and the sheet is monolayer.While the time of solvothermal is increased,the crystallinity of the material is increased,the thickness of the nanosheet is also increased,and the performance of the photocatalytic reduction of CO₂ is reduced.The BM-3h has the best performance of photoreduction CO₂,the yields of methanol and ethanol were 106.5μmol gcatal.^-1and10.3μmol gcatal.^-11 respectively,after 4 hours photoreaction.