Synthesis Of Bismuth Oxyiodide Based Photocatalysts And Study On The Photocatalytic Activities

Bismuth oxyiodide is regarded as promising photocatalysts for its favorableproperties such as narrow band gap, layered structure, and strong inner static electricfield. In this work, pure BiOI photocatalysts are synthesized by one-step hydrothermalmethod and two step liquid phase-hydrothermal method, BiOBr_xI_1-x（x=0.0,0.3,0.5,0.7,1.0） solid solutions are prepared by two step liquid phase-hydrothermal method,and BiOI/BiOBr using CTAB as Br source. The crystal structure, morphology andelement compositions of the obtained catalysts were characterized by XRD, UV-Vis,SEM, TEM, and EDS, respectively. The photocatalytic activities of the samples wereestimated from the photodegradation of methyl orange （MO） under irradiation withvisible light.The pure BiOI photocatalyst synthesized by liquid phase-hydrothermal methodexhibit a three-dimensional flower-like morphology composed of several nanoflakeswith a thickness of⁷0nm. The composed nanoflakes are monocrystalline with {001}planes exposed, revealing the direction of growth perpendicular to [001] crystaldirection. The as-prepared sample showed higher photocatalytic activities than thesample prepared via a simple hydrothermal method, which could achieve thedegradation of100ml10mg·L^-1MO aqueous within40min. In the process ofphotocatalytic reaction, exited eletrons react with dissolved O2to produce O2· andtogether with the photogenerated holes react with MO molecules, which leading to thephotodegradation of MO aqueous.BiOBr_xI_1-x（x=0.0,0.3,0.5,0.7,1.0） solid solutions were synthesized by liquidphase-hydrothermal method.XRD patterns of the solid solutions shifted between the twopure phases and exhibit a three-dimensional flower-like morphology composed ofseveral nanoflakes with a thickness of⁷0nm. Four elements were uniform distributedin the solid solution, adjusting the band structure and light absorption efficiently.Compared to the pure BiOI and BiOBr, BiOBr_0.3I_0.7solid solution showed excellentphotodegradation activities, which could lead to the degradation of MO within20min.The valent band position of solid solutions are more positive than BiOI, which madethem generate stronger oxidizing holes in the photocatalytic reactions.BiOI/BiOBr photocatalysts were prepared via hydrothermal method using CTAB asBr source and surfactant.30%BiOI/BiOBr displayed higher photocatalytic activitiesthan pure BiOI, BiOBr and the same ratio BiOI/BiOBr with KBr as Br source. The photocatalysts could achieve the degradation of MO within40min under visible lightirradiation.