Fabrication Of Heterojunction Based On Bismuth Oxyiodide And Study On The Photodegradation Properties

Semiconductor photocatalysts have great application in the utilization of solarenergy and the oxidative degradation of pollutants. As one of the commonphotocatalytic material, TiO₂has advantages of relatively high activity, goodstability and chemical resistance. However, it only responds to ultraviolet light,which accounts for a mere fraction of sunlight. Besiedes, electron-hole separationefficiency of TiO₂is rather slow. Owing to these factors, the development ofphotocatalytic material who has the ability to response in visible is necessary. Asone of the novel photocatalysts, BiOI exhibits relatively superior performance onphotocatalytic degradation of organic pollutants. The reason for its highperformance is special layered structure. Meanwhile construction of heterojunctionstructure has proven to be a rather useful method to separate photo-generatedelectron-hole, further to improve the photocatalytic property.BiOI and its heterostructure photocatalyst were prepared using solvothermalmethod. XRD, SEM, TEM, BET, FT-IR, XPS and other characterizations were usedto characterize the structure and morphology. Four common dyes （rhodamine B,methylene blue, methyl orange and acid fuchsin） were used as models to study thephotocatalytic performance under visible irradiation.BiOI nanosheets were prepared through precipitation-solvothermal method.As-prepared samples were characterized and characterization results are as follows.Samples prepared with assitance of surfactants show thinner nanosheet structure,and BiOI-20has the thinnest thickness of about30nm. Specific surface area, porediameter, and the light absorption of BiOI-20are smaller than BiOI-0. However,samples prepared with asstance of PVP（BiOI-20） has superior adsorption andphotocatalytic property compared to BiOI-0, and the degradation rate constant ofBiOI-20is46times than BiOI-0. FT-IR and XPS were used to study the possiblebonding mode between PVP and BiOI, and the results indeicate that PVP iscombined with BiOI through hydrogen. Zeta potential tests showed BiOI-20had amore negative charge compared with BiOI-0. Thinner nanosheet structure, excellentadsorption performance and unique electron structure give BiOI-20a more excellentphotocatalytic property.BiOIxPhotocatalyst were prepared in the presence of surfactant PVP. Iodinedoping could improve the crystallinity of the photocatalyst, and iodine-dopingincreased the thickness of samples compared to the undoped one. BiOI_1.3showedmost outstanding performance, and the higher doping is harmful for photocatalyticperformance.Solvothermal method was successfully used to build BiOI/Bi₂O₂CO₃ heterostructure photocatalyst. XRD and HRTEM showed evidence for the existenceof the heterojunction structure. SEM result reveals that as-prepared samples arenanoflower-shaped structure composed by nanosheets. Samples prepared with citricacid alone have better adsorption and photocatalytic performance than the samplesprepared with adding urea and citric acid. When the ratio of BiOI and Bi₂O₂CO₃is5:5, sample possessed the best adsorption and photocatalytic performance could beobtainded. Photocatalytic performance of heterostructure in photodegradingmethylene blue, methyl orange, acid fuchsine are higher than the pure BiOI andBi₂O₂CO₃substance.