Microwave-assisted Preparation Of Zn/S Co-doped BiOI And Study On Visiblelight-driven Photocatalytic Performance And Mechanism

Due to the characteristics of wide varieties,hard degradation,wide distribution and easy enrichment,organic pollution of water body has caused great harm to the human ecological environment.Semiconductor photocatalytic technology has shown great potential in removing organic pollutants due to its advantages of green,low energy consumption,strong oxidation capacity and mild reaction conditions,and has become a research hotspot.The core of this technology is to design and prepare high-efficiency and stable photocatalysts.In this paper,microwave-assisted precipitation method was used to prepare Zn/S co-doped BiOI（Zn/S-BiOI）photocatalyst,and the photocatalytic system with bisphenol A（BPA）in water as the main target contaminant was established.The visible-light photocatalytic performance was tested.The mechanism of visible-light photocatalytic degradation of BPA by Zn/S-BiOI was also discussed.Zn/S-BiOI photocatalyst was prepared by microwave-assisted precipitation method.The preparation conditions of Zn/S-BiOI were optimized,and the optimal preparation conditions were as follows: the molar ratio of Zn source/Bi source was 1/2,the microwave reaction temperature was 60 ℃,the microwave reaction time was 40 min,and the p H value of the precipitation reaction was 5.Characterizations of XRD,SEM,TEM,EDS,XPS,FTIR,BET,UV-VIS DRS and PL were used to characterize the structure of BiOI and Zn/S-BiOI.The results showed that the doping of Zn/S promoted the formation of defects and oxygen vacancies.The microstructure showed the three-dimensional irregular spherical structure formed by the connection of ultrathin nanosheets with rough surface.The specific surface area（92.0 m²/g）was greatly increased and the pore structure was suitable（mainly distributed at 2.5 nm and 8.6 nm）.The visible-light photocatalytic performance of the optimized Zn/S-BiOI was studied.The results showed that the degradation rate of BPA by Zn/S-BiOI radiated under simulated visible light for 2 h could reach nearly 90%,and the photocatalytic reaction rate(0.01829 min^-1) of pseudo-first-order reaction kinetics was about twice that of pure BiOI(0.00949 min^-1).It also had excellent recyclability and stability（the degradation rate remained nearly 90% after 5 repeats）.Moreover,Zn/S-BiOI had good adaptability under weak acidic to neutral conditions.The mechanism of visible-light photocatalytic degradation of BPA by Zn/SBiOI was investigated systematically.According to the trapping experiments of active species and combined with EPR detection technology,the active species playing the main role in the photocatalytic system were ·O₂^- and holes.Based on the energy band structure,the photocatalytic degradation mechanism of BPA by Zn/S-BiOI was further analyzed.The Mulliken population analysis and Fukui index of BPA were calculated by density functional theory（DFT）to analyze the degradation sites of BPA,with that the intermediate products and degradation pathways of BPA were predicted.