Study On The Synthesis Of WO₃/BiOBr Photocatalyst And Its Photocatalytic Activity Driven By Visible Light Irradiation

Photocatalytic technology has become a research hotspot because of its advantages of high efficiency,energy and environmental pollution.The study found that halogenated bismuth oxide（BiOX,X=Cl,Br,BiOX,Ⅰ）is a new type bismuth catalyst that could response to visible light.BiOX have special layer structure,can promote the separation of photogenerated electrons and holes.The BiOBr is known as promising in the simple P type semiconductor photocatalytic material with visible light response.In order to further improve its photocatalytic activity and stabilization,considered to be combined with another traditional narrow band semiconductor catalyst WO₃.Therefore,compositing BiOBr and WO₃ improve the charge separation efficiency of photo-generated electron-hole pairs and then enhance the quantum efficiency.In this paper,different n（W）:n（Br）ratio of WO₃/BiOBr photocatalyst was synthesized by one-step hydrothermal synthesis using Bi（NO3）3·5H2O,NaBr and H2WO4 as raw materials.The prepared photocatalysts were characterized by XRD,SEM,TEM,UV-vis DRS,XPS and BET surface area analysis.Investigated the effects of catalyst dosage,pH value of solution and salt on the catalytic activity.At the same time,the stability of WO₃/BiOBr was investigated.The results of this study show that:（1）Using methyl orange as probe pollutants,in visible light degradation of methyl orange experiments,the optimum synthesis condition of WO₃/BiOBr was selected as:n（W）:n（Br）=2%,the pH value of hydrothermal precursor = 10.3,hydrothermal synthetic temperature-100 ℃,hydrothermal holding time =6 h.Due to the narrow band gap and high specific area,after visible-light illumination for 2 hour,the degradation rate of 20 mg/L methyl orange solution can amount to 99.63%,compared with BiOBr photocatalytic activity increased by 30.85%.（2）Photocatalytic degradations of methyl orange were performed to investigate the influence of different conditions.The results showed that:methyl orange solution pH of weak acid conditions,initial concentration of solution was 20 mg/L,adding 0.2g/L WO₃/BiOBr catalyst,the removal rate of methyl orange is above 99%;NaCl for methyl orange degradation has certain inhibitory effect;repeated use experiments show that the structure of WO₃/BiOBr photocatalyst is stable and can be used repeatedly.（3）In the degradation of nitrophenol and Eosin B,WO₃/BiOBr visible-light photocatalytic properties have been further investigated.After visible-light illumination for 3 hour,20 mg/L nitrophenol decolorization rate can reach 89.05%;After visible-light illumination for 1 hour,decolorization rate of 20 mg/L Eosin B can reach 98.5%.Results showed the excellent photocatalytic activity and stabilization of WO₃/BiOBr to degredate nitrophenol and Eosin B.（4）Photocatalytic degradation of methyl orange,nitrophenol and Eosin B accord with pseudo-first-order reaction kinetics equation.This topic research will further widen the Bismuth photocatalyst research field,and the research result has a certain theories guide and realistic meaning to the treatment of dye wastewater and other refractory organic pollutants.