Studies On Preparation And Photocatalytic Performance Of BiOBr-based Nanocomposites

With the rapid development of industrialization and urbanization,environmental protection has become a hot issue.Various organic dyes are randomly discharged into water bodies,which can cause a serious threat to aquatic life and human body.In recent years,bismuth oxyhalide has attracted researchers'attention because of its unique electronic structure,chemical stability,and efficient photodegradability.Nevertheless,pure BiOBr exhibits terrible photocatalytic efficiency,which maybe ascribed to its low quantum efficiency.Great efforts have been taken to improve the photocatalytic performance.In this work,we have successfully prepared the flower-like BiOBr/GCN nanosheets heterojunction,rare earth Gd³⁺ions doped BiOBr nanosphere and La³⁺ions doped flower-like BiOBr nanosheets.The X-ray diffraction,scanning electron microscope,transmission electron microscopy,UV-Vis diffuse reflection and X-ray photoelectron spectroscopy are used to characterize the material's crystal structure,morphology,chemical state and band-gap structure,respectively.Moreover,methyl orange(MO),Rhodamine B(Rh B),bisphenol a and carbon dioxide reduction are used to investigate photocatalyst's degradation efficiency.(1)The high recombination rates of photogenerated electron-holes greatly inhibit the catalytic activity of semiconductor photocatalysts.Herein,the heterojunctions of the flower-like BiOBr/GCN are synthesized as photocatalysts by a simple hydrothermal process.The X-ray diffraction,scaning electron microscopy,and X-ray photoelectron spectrometer are utilized to characterize the sample's structure and light absorption properties.The results demonstrated that BiOBr/GCN-4:1 shows excellent photocatalytic properties and 96.6%of bisphenol(BPA)is removed in 120 min with illumination of visible light due to its narrower band gap than that of pure BiOBr.Moreover,the heterostructure between BiOBr and GCN facilitates the separation of photogenerated carriers.Excellent stability is exhibited after five cyclic degradation with the illumination of visible light.(2)BiOBr and La doped BiOBr are synthesized via a hydrothermal method.The crystallinity,morphology,elemental composition and band-gap structure are characterized via XRD,SEM,XPS and UV-Vis diffuse reflection spectrum.The resulting La doped BiOBr exhibits an obvious decrease in crystallinity compared to bare BiOBr.The La³⁺is found to exist on the BiOBr in the form of La₂(CO₃),and a tiny number of La are doped into BiOBr lattice.Moreover,BiOBr/La-4.9%exhibits the best photocatalytic performance in converting CO₂ into methanol.The improved performance is ascribed to the enhanced visible-light absorption and narrow band-gap structure after La³⁺doping.(3)Rising carbon dioxide(CO₂)levels in the atmospheric environment is a key cause of global warming.To reduce the concentration of CO₂ in the atmosphere,converting CO₂ into hydrocarbon fuels is an eye-catching strategy.We achieve in-situ doping of Gd³⁺for BiOBr microspheres consisting of nanosheets via a simple hydrothermal method.The resulting Gd doped BiOBr structure exhibits considerable improvement on the photocatalytic activities for CO₂ reduction.Compared to bare BiOBr(24.097?molg^-1 for 3 h),the BiOBr/Gd-0.05 exhibits excellent performance of CO₂reduction with nearly five-fold increase in the rate of methanol emission(123.711?molg^-1for 3 h).The enhanced CO₂ reduction activities of BiOBr/Gd-0.05 are attributed to the mechanism that Gd³⁺ions are introduced into the lattice of BiOBr to broaden the visible light response,form a narrow band gap.