Preparation Of Novel Bismuth Oxyhalide Composite Photocatalytic And Thier Photocatalytic Properties

This thesis is based on the application of bismuth oxyhalide in photocatalysis.In this study,a series of preparation method for bismuth oxyhalide composite photocatalysts were designed,the morphology,photochemical,electrochemical properties,etc.of these photocatalysts were characterized,the degradation efficiency and cycling stability of Rhodamine B?RhB?and tetracycline?TC?for these were studied,the catalytic reaction mechanism of these photocatalysts systems were further proposed.The specific research contents were briefly described below:The BiOI/Bi₂O₂CO₃ binary composite photocatalysts were constructed by anion exchange method.Then,the surface of the binary complexes were modified to form negatively charged complexes.Finally,these binary complexes were combined with graphene?RGO?to form amino-functionalized?Ami-?BiOI/Bi₂O₂CO₃/RGO ternary composites through electrostatic self-assembly strategy,which makes the close interface contact between RGO and?Ami-?BiOI/Bi₂O₂CO₃.A series of experimental test indicating the binary composites showed more excellent photocatalytic activity for the degradation of RhB and TC than BiOI and Bi₂O₂CO₃ photocatalyst,which was depended on the formation of a p-n junction between BiOI and Bi₂O₂CO₃ photocatalyst to promotes the separation of photogenerated carriers;the degradation efficiency of RhB and TC by ternary composites showed higher photocatalytic property than the binary composites and the unmodified ternary materials,suggesting that photocatalyst loaded RGO could enhance the transfer rate of electron-hole on the heterojunction and he carrier mobility was further improved after recombination with the amino-functionalized semiconductor materials.Three types of bismuth oxyhalide?BiOI,Bi₄O₅I and Bi₅O₇I?with different elemental stoichiometry were successfully prepared with pH modulated by the solvothermal methods,with special and uniform morphologies.Their photocatalytic efficiencies were better than the previous flake BiOI because the incident light was repeatedly refracted owing to the hierarchical 3d structure and more active species and reactant molecules can be absorbed on the surface of these porous microspheres with large surface area,which further increasing a number of charge carriers.Moreover,part of Bi₄O₅I₂ photocatalyst precursor was converted into Bi and Bi₅O₇I forming Bi/Bi₄O₅I₂/Bi₅O₇I composite photocatalysts in virtue of NaBH₄ as a reducing agent and CTAB as a template.It was found that Bi/Bi₄O₅I₂/Bi₅O₇I composite photocatalyst exhibited higher photocatalytic degradation efficiency for RhB and TC under visible light irradiation for the synergistic effect of bismuth nanoparticles providing surface plasmon resonance effect and Bi₄O₅I₂/Bi₅O₇I homotypic heterojunction.The ultrathin BiOBr nanosheets with uniform size and good dispersion,were prepared by hydrothermal method with CTAB as bromine source and template.The Cu₂O/BiOBr and Cu/Cu₂O/BiOBr composite photocatalysts were prepared by adjusting the amount of reducing agent with CTAB as chelating agent.The size of the Cu₂O was uniform and the dispersion was good that shows the presence of CTAB inhibited the reduction capacity of N₂H₄.The photocatalytic experiments indicated that Cu/Cu₂O/BiOBr composite photocatalysts showed the highest degradation efficiency for TC under visible light irradiation,which was attributed to the response range of light broaden by the heterojunction,while the surface plasmon resonance effect caused by Cu as cocatalyst further promoting the electron transfer rate on the surface of Cu₂O/BiOBr heterojunction.The radical capture experiments revealed that the main active species in the photocatalytic degradation process were h⁺,·O₂^-and·OH.On the basis of these experiment,we proposed the possible electron transfer path,and designed a novel Z type heterojunction system well explaining the experimental results.