Preparation Of Two Kinds Of Oxide/Graphene Quantum Dots/Mesoporous Titanium Dioxide Photocatalysts And Their Application In Photocatalytic Epoxidation Of Styrene

Mesoporous titanium dioxide（m-TiO₂）had always been one of the hotspots of research scholars because of its adjustable band gap,excellent electronic and optical properties,etc,and it was suitable as an excellent photocatalyst for photocatalysis.Graphene quantum dots（GQDs）with fast electron migration rate,excellent mechanical strength,and a particle size value of 13.8 nm with zero band gap was doped on m-TiO₂in order to overcome its own limitations,such as a wide band gap,ultraviolet light absorption in the range and rapid electronic recombination,etc.It can improve its visible light irradiation for the purpose of making full use of green and clean solar energy.The new ZnO/GQDs/m-TiO₂ was improved by the sol-gel method,and the V₂O₅/GQDs/m-TiO₂ composite photocatalyst was improved by the hydrothermal method for exploring photocatalysis at room temperature Epoxidation of styrene and its catalytic mechanism.The primary studies were as follows:1.Preparation and characterization of ZnO/GQDs/m-TiO₂ and its application in photocatalytic epoxidation of styreneA series of ZnO/GQDs/m-TiO₂ photocatalysts with different loading of ZnO were synthesized by Sol-gel method.Then its structure and morphology was tested by X-ray diffractometer（XRD）,Fourier transform infrared spectroscopy（FT-IR）,transmission electron microscope（TEM）,etc.X-ray photoelectron spectroscopy（XPS）was explored the surface chemical state and chemical bonds of the elements.The experimental results confirmed that superoxy radical（·O₂^-）was the active substance of the reaction.Electron paramagnetic resonance（EPR）was explored the active substance of the reaction,and the experimental results confirmed that superoxy radical（·O₂^-）was the active substance of the reaction.And speculate the possible mechanism of the reaction,at the same time the photocatalytic styrene epoxidation activity of the synthesized catalyst was studied.It can be seen from the experimental results that ethanol was used as the solvent for the reaction,and the amount of the catalyst was 75mg,the loading of ZnO was 7%,the photoreaction was 3 h,the number of cycles was 5,and the n H₂O₂/n Styrene was 4,the experimental results were the best.2.Preparation and characterization of V₂O₅/GQDs/m-TiO₂ composite photocatalyst and its application in photocatalytic epoxidation of styreneA series of V₂O₅/GQDs/m-TiO₂ photocatalyst was synthesized by hydrothermal method,and its structure and morphology were studied by XRD,FT-IR and TEM.XPS was explored the chemical state and chemical bond of its element surface.The EPR test results showed that the active species was·O₂^-,and speculated the mechanism of the catalyst in the photocatalytic epoxidation of styrene.At the same time,the photocatalytic activity of the synthesized catalyst was studied,Such as the effective component V₂O₅ content,proton and aprotic solvents,molar ratio（H₂O₂/styrene）,photocatalytic oxidation time,catalyst usage and cycle times.It can be seen from the experimental results that ethanol was used as the reaction solvent,the loading of V₂O₅was 9%,the catalyst mass was 50mg,the n H₂O₂/n Styrene was 1,and the photoreaction took 1 h,the experimental results were the best.