Synthesis Of Bismuth Oxyhalides Photocatalyst And Investigation Of Visible-Light Photocatalytic Performance

The development of modern industry brings about great wealth for human beings,but it also brings about serious pollution problems.Particularly,the waste water discharged in the industrial production process contains plenty of excess contaminants,and some of them exhibit strong carcinogenesis,mutagenesis and sterilization properties.If the industrial waste water was directly discharged into the rivers,it would lead to the serious damage to the ecological environment,and it would further endanger the healthy of humans and other creatures on earth.Therefore,it undoubtedly is the“green engineering”benefiting the earth to remove the organic pollutant contaminants in industrial waste water by utilizing the effective methods while keeping the sustainable development of the economy.Research shows that photocatalytic degradation technology is one of the most effective and simplest methods to remove the excess organic pollutant contaminants in industrial waste water in current for its low operating cost and without secondary pollution.Most of traditional photocatalysts exhibit superior UV-light response,but the UV-light energy only occupys about 4⁵%of the sunlight energy,and the visible-light energy can occupy about 43%of the sunlight energy.Obviously,it is extremely disadvantageous to the application extension of traditional photocatalysts.Therefore,exploring the efficient paths to improve the visible-light response of traditonal photocatalysts is the research focus of research fields at present.In recent years,numerous researchers had carried out plenty of works in the synthesis of the photocatalysts with superior visible-light response,and some novel photocatalyst materials with favorable visible-light response and photocatalytic activity were successfully reported.However,to majority of the photocatalysts,the recombinations of photoexcited electron-hole pairs would easily happen when the photoexcited electrons and holes were produced after being excited,and it would seriously weaken the utilization efficiency of photoexcited charge carriers of the photocatalysts.Therefore,some effective methods should be carried out to inhibit the recombinations of photoexcited electron-hole pairs for improving the photocatalytic efficiency of the photocatalysts under visible-light irradiation.To improve the visible-light response and interfacial charge transfer ability of the photocatalyst materials is the most effective methods for enhancing the visible-light photocatalytic performance of the photocatalysts.This paper mainly aims to improve the visible-light photocatalytic performance of bismuth oxyhalide semiconductor photocatalysts,and the systematic research about the composition,architecture design,preparation and characterization of bismuth oxyhalide composite photocatalysts was carried out.The preparation of heterojunctions（BiOBr-Co（OH）₂ and BiOCl-TiO₂）,introduction of carrier materials with unique structures（rattle-type magnetic mesoporous silica microsphere and hollow mesoporous silica microsphere）,introduction of quantum size effect and plasmonic effect（preparation of BiOBr nanophotocatalyst with quantum size and introduction of noble metal Pd nanoparticle and Bi plasma）and application of up-conversion photoluminescence and conducting polymer（introduction of the carbon quantum dots with up-conversion photoluminescence and polyaniline with conducting property）were investigated respectively,and a series of novel photocatalyst materials（BiOBr/β-Co（OH）₂,BiOCl/TiO₂,Fe₃O₄@mSiO₂@BiOBr,H-mSiO₂-BiOBr H-mSiO₂@BiOCl/PANI/Pd and Bi/BiOCl/TiO₂-CQDs）with more superior performance than traditional bismuth oxyhalide photocatalysts were synthesized successfully.Due to the formation of the narrow bandgap and interacted interfaces originated form the generation of BiOBr-β-Co（OH）₂ and BiOCl-TiO₂ p-n heterojunctions,the synthesized BiOBr/β-Co（OH）₂and BiOCl/TiO₂ hierarchical photocatalysts exhibited superior visible-light response and photocatalytic performance.The unique internal cavity structure of the rattle-type magnetic mesoporous silica microspheres and hollow mesoporous silica microspheres can produce obvious concentration gradient effect,and the organic pollutant contaminants in the degradation system can be effectively enriched.Simultaneously,the irradiated light can be reflected repeatedly by the internal cavity,so that the action time of the irradiated light can be prolonged effectively,then the visible-light response of the photocatalyst can be enhanced significantly.The introduction of superparamagnetic nuclei can endow the photocatalyst superior magnetic separation characteristic,and the nanocrystallization of BiOBr semiconductor can effectively enlarge the bandgap width after being excited,so that the recombinations of photoexcited electron-hole pairs can be suppressed effectively.Therefore,both the rattle-type Fe₃O₄@mSiO₂@BiOBr photocatalyst and hollow mesoporous H-mSiO₂-BiOBr nanophotocatalyst exhibited ultrastrong enrichment ability of organic pollutant contaminants and enhanced visible-light photocatalytic performance.The conducting polymer and BiOCl doped by noble metal palladium were introduced into the hollow mesoporous silica sub-microsphere system,the generation frequency of the photoexcited carrier and the separation efficiency of the photoexcited electrons and holes can be effectively improved for the superior plasma effect of the noble metal Pd and the fast interfacial charge migration of the polyaniline.The superior visible-light response and upconversion property of carbon quantum dots can effectively improve the visible-light response of BiOCl/TiO₂ nanosheets.The surface plasmonic resonance effect of the Bi co-catalyst generated in the BiOCl/TiO₂ matrix can further enhance the light response property of the photocatalyst.For the formation of the Bi/BiOCl-TiO₂-CQDs quaternary heterojunction,it exhibited superior interface charge transfer ability and can effectively suppresstherecombinationsofphotoexcitedelectron-holepairs,thusthe Bi/BiOCl/TiO₂-CQDs photocatalyst exhibited superior visible-light photocatalytic performance.When the photocatalytic performances of the photocatalysts were investigated,the main active species in the photocatalytic process were also investigated,and the corresponding photocatalytic mechanism were explained accordingly.