Study On The Synthesis And Visible-light Photocatalytic Activity Of Bi-based Composites

Bi-based semiconductor photocatalytic materials have attracted much attention owing to their appropriate band gap and unique structure.However,for pure phase Bi-based semiconductor photocatalytic materials,they suffer some drawbacks,including low visible light utilization owing to wide band gaps,and high recombination rate of the photogenerated electron-hole pairs,and restricts its practical applications.In this paper,BiFeO₃ and BiOBr were studied because of their chemical stability,proper bandgaps for light absorption and environmentally friendly properties.A series of appropriate modifications were carried out in the paper to overcome the shortcomings.The main work and results are introduced as follows.（1）The uniform dispersion of hollow microspheres BiOBr^-Sepiolite Composite Photocatalysts were prepared by solvothermal method with polyvinyl pyrrolidone（PVP）assisted.The structure,morphology and optical properties of composite photocatalysts were characterized by SEM,XRD,UV-Vis,FTIR and other techniques.The results indicate that The modified composite catalyst could reduce agglomeration、 improve visible light absorption and inhibit the recombination of electron-hole pairs.（2）The degradation of rhodamine B were studied to determine the optimal blending rate of acidized sepiolite.When the content of AS was 6%,the PVP/AS/Bi OBr composite showed the highest photocatalytic degradation rate about 100%,TOC removal rates was 75%,which was superior to the pure BiOBr obviously.The optium reaction conditions for PVP/AS/BiOBr were studied,and the results showed that when the catalyst dosage was 1.0g/L,the initial concentration of 10mg/L,,the solution pH of 5,the photocatalytic activitie was better.The degradation of diclofenac sodium aqueous solution by PVP/AS/BiOBr showed the composite catalyst had wide application scope.（3）The rhombohedral BiFeO₃/Cd S heterojunction composite photocatalyst were prepared by hydrothermal method.The structure,morphology,specific area and optical properties of composite photocatalysts were characterized by SEM,XRD,BET,UV-Vis and other techniques.The degradation of rhodamine B were studied to determine the optimal blending rate of CdS.The results showed that the activity and stability of BiFeO₃/CdS were all improved,which solved the problems,including low photocatalytic performance of BiFeO₃ and the photocorrosion of CdS.（4）In the measurement of reactive radical formation,O2·-、h+、·OH are involved in the process of the degradation of RhB by PVP/AS/BiOBr,and O2·-showed the maximum contribution rate.And O2·-plays a major role in the BiFeO₃/CdS photocatalytic reaction.（5）The GC-MS and UV-Vis DRS showed that the RhB degradation starts with N-de-ethylation,followed by the ring opening.Hydroquinone,Oleic acid,and Palmiti acid were produced.Subsequently,these compounds were further decomposed into smaller molecules,such as Adipic acid and Glutaric acid,which were further mineralized into CO2 and H2 O.