Preparation And Photocatalytic Performance Of BiOCl-based Composites

As a semiconductor photocatalyst,Bi OCl has a unique layered structure,which is easy to prepare and chemically stable.However,the wide band gap and narrow light absorption region of Bi OCl,and the easy combination of photogenerated electrons and holes severely affect the photocatalytic activity of Bi OCl.Therefore,in order to improve the photocatalytic performance of Bi OCl-based nanomaterials,this paper firstly explored the synthesis of small-sized Bi OCl nanosheets,and then deposited Bi OCl nanosheets onto Cs/Mn O₂ porous templates and flower spherical Bi₂WO₆ templates by precipitation method to prepare Cs/Mn O₂/Bi OCl and Bi₂WO₆/Bi OCl composites,respectively.The effects of factors such as composition and microstructure of the composites on the photodegradation performance of different organic pollutants are investigated as follows:（1）Bi OCl nanosheets are synthesized with an average thickness of 50 nm and 10 nm by the solvothermal and precipitation methods,respectively.The photocatalytic performance tests showed that the thickness of the Bi OCl nanosheets affected their photocatalytic activity,and the thin Bi OCl nanosheets synthesized by the precipitation method showed a better photocatalytic performance than the thick nanosheets synthesized by the solvothermal method.Under UV light irradiation,the precipitated Bi OCl nanosheets degraded 95%of rhodamine B in 35 min and over95%of MB in 45 min.The excellent photocatalytic performance can be attributed to the thin thickness,smaller particle size and larger specific surface area of the precipitated Bi OCl nanosheets.（2）Porous C_S/Mn O₂ composites are prepared by using carbon nanosheets（Cs）prepared by high-temperature carbonization as reducing agents and sacrificial templates,and the Cs/Mn O₂/Bi OCl ternary composites are prepared by chemical deposition on this substrate.By adjusting the loading of Bi OCl,the optimized Cs/Mn/Bi-1/1 composites exhibited the highest photocatalytic activity and excellent cyclic degradation performance.Under UV light irradiation,97%of rhodamine B was degraded in 25 min,98%of methylene blue in 40 min and 80%of tetracycline hydrochloride in 30 min.The degradation rate constants are 0.129,0.081 and 0.038min^-1,respectively,and the photocatalytic mechanism is verified as a Z-type heterojunction transfer mode based on the electron spin resonance results.The excellent photocatalytic performance depends on the formation of Z-type heterojunctions between Mn O₂ and Bi OCl.In addition,the conductive carbon layer reduces the charge transfer resistance and accelerates the separation and transfer efficiency of photogenerated carriers.（3）Bi₂WO₆ hydrangeas are firstly synthesized by hydrothermal method and used as porous templates.Hydrangea-like Bi₂WO₆/Bi OCl composites with porous nanostructures are synthesized by changing the concentrations of Bi³⁺and Cl^-precursors.Under visible light irradiation,the optimized Bi₂WO₆/Bi OCl-1/1 composite degrades 100%of rhodamine B after 60 min,88%of methylene blue after 75 min and 90%of tetracycline hydrochloride after 90 min,which are far superior to pure Bi₂WO₆ and pure Bi OCl.Their excellent photocatalytic performance is attributed to the hydrangea-like microstructure and the formation of Z-shaped heterojunctions.There are 43 figures,5 tables,and 118 references in this paper.