Preparation And Photocatalytic Properties Of Fluorine/Sulfur Doped Bi₂WO₆

With the continuous development of the industry,the discharged wastewater contains various pollutants,including some heavy metals,organic dyes,etc.Cr（Ⅵ）is included in the list of toxic pollutants due to its potential carcinogenicity and persistent environmental hazards.Dyestuffs and Cr（Ⅵ）often coexist in industrial wastewater.Methyl orange（MO）is a refractory azo colored compound and is representative of similar dyes.Semiconductor photocatalysis technology is considered as one of the effective means to remove Cr（Ⅵ）and dyes simultaneously.As a typical Aurivillius layered perovskite material,bismuth tungstate（Bi₂WO₆）has attracted much attention due to its unique layered structure,thermal and photochemical stability,and environmental friendliness.However,limited visible light absorption and slow separation of photogenerated carriers hinder its practical application.In this paper,using Bi₂WO₆ as the substrate and adopting the doping strategy of non-metal elements,the energy band structure of Bi₂WO₆ was optimized to obtain F,S doped nano-Bi₂WO₆photocatalytic materials,and their visible light catalysis for Cr（Ⅵ）reduction and MO degradation was studied.performance,and explore ways to improve its visible light catalytic efficiency.The main research contents and results are as follows:1.F-doped Bi₂WO₆ photocatalyst（F-Bi₂WO₆）was prepared by a hydrothermal method by modulating the amount of F doping,and MO and Cr（Ⅵ）were used as target pollutants to explore the visible light catalytic reduction and degradation of Cr（Ⅵ）.MO activity.Studies have shown that the amount of F doping is closely related to the morphology and photocatalytic activity of F-Bi₂WO₆.The introduction of an appropriate amount of F ions can change the electronic structure of Bi₂WO₆ crystals,induce oxygen vacancies,reduce the band gap,and obtain red blood cell-like F-Bi₂WO₆ nanosheet catalyst,thereby accelerating the migration rate of photogenerated carriers and promoting the effective separation of photogenerated carriers,enhancing the photocatalytic activity.The optimized F_1.0-Bi₂WO₆ achieved 93.9%Cr（Ⅵ）reduction and 90.1%MO degradation within 120 min.2.In addition to reducing the forbidden band width of Bi₂WO₆ by doping with halogen elements,broadening the visible light absorption range and promoting the effective separation of photogenerated carriers,the activity of S doping on Bi₂WO₆catalytic reduction of Cr（Ⅵ）and degradation of MO under visible light was studied.The results showed that proper doping of S atoms could change the electronic structure of Bi₂WO₆ and induce oxygen vacancies,but did not affect its morphology and structure,and the band gap of S-Bi₂WO₆ was further reduced than that of F-Bi₂WO₆,and the photocatalytic oxidation activity was significantly improved.Reduced reducing activity.The optimized S_0.90-Bi₂WO₆ had a Cr（Ⅵ）reduction rate of 88.2%within 120 min,and a MO degradation rate of 97.6%within 75 min.3.A photocatalyst（S/F-Bi₂WO₆）co-doped with S and F was prepared.After characterization and theoretical analysis,the material still has good stability while maintaining high catalytic activity.The separation of photogenerated electron-hole pairs is promoted,the recombination rate of carriers is reduced,and the photocatalytic activity of the material is improved.The photocatalytic performance of the material was investigated by the oxidation of methyl orange MO and the reduction of Cr（Ⅵ）.The results showed that the S_0.10F-Bi₂WO₆ material had the highest photocatalytic activity,which can achieved 94.3%Cr（Ⅵ）reduction and 95.4%MO degradation within 120min.