Synthesis Of Bi₂₄O₃₁Br₁₀ And Its Composites And Their Photocatalytic Degradation Properties Of Pollutants

Since the 21st century,with the rapid development of economy and society,environmental pollution has become increasingly serious.Semiconductor photocatalysis,as a new technology with low energy consumption,good stability,clean and pollution-free,has attracted wide attention in the field of environmental pollution control.However,most photocatalysts have the shortcomings of narrow light response range and high recombination efficiency of photogenerated carriers,which limit their practical application.Therefore,Bi₂₄O₃₁Br₁₀ with visible-light photocatalytic activity and high thermal stability was studied in this paper.The influence of preparation methods on photocatalytic performance of semiconductor materials was discussed,and the reaction mechanism was studied.In addition,the photocatalytic activities of Bi₂₄O₃₁Br₁₀ were improved by means of recombination with other materials,from the two perspectives of broadening the light response range of Bi₂₄O₃₁Br₁₀ to near infrared region and improving carrier separation efficiency.The main research contents and conclusion are as follows:?1?Bi₂₄O₃₁Br₁₀ samples rich in oxygen vacancies were successfully prepared by adjusting pH at room temperature using mixed solution of water and glycerol as solvents.In addition,Bi₂₄O₃₁Br₁₀ samples with higher crystallinity were prepared by solvothermal method and high temperature calcination method respectively for comparison.The effects of different preparation methods on photocatalytic performance of Bi₂₄O₃₁Br₁₀ were investigated with simulated solutions of refractory organic pollutants and low concentration flowing NO as the target pollutants.The experimental results show that the Bi₂₄O₃₁Br₁₀ samples synthesized by simple room temperature precipitation method have better visible-light photocatalytic activity than the other two samples synthesized by high temperature methods.By test of XRD,SEM,TEM,TG/DTG,XPS,DRS,PL and photoelectrochemical characterization,the phase composition,morphology,thermal stability and optical properties of Bi₂₄O₃₁Br₁₀ were analyzed.The synthesis mechanism of Bi₂₄O₃₁Br₁₀ and the reasons for the difference of photocatalytic properties of the three samples were studied.It was found that the BOB-R sample had the best photocatalytic activity because of its smaller particle size,more negative conduction band position and the richest oxygen vacancy content.?2?Up-conversion phosphor/Bi₂₄O₃₁Br₁₀ composite was successfully prepared at room temperature by precipitation stirring method.The experimental results of photocatalytic oxidation of flowing NO under different wavelength of lights show that the composite not only has excellent photocatalytic oxidation activity under ultraviolet and visible light,but also exhibits a certain catalytic oxidation performance driven by near infrared light.The analysis of photoluminescence spectra and ultraviolet-visible diffuse reflectance indicates that the light response range of up-conversion phosphor/Bi₂₄O₃₁Br₁₀ composite has been successfully extended to the near infrared region to achieve broad spectral response under the unique near infrared conversion ability of the up-conversion phosphor.?3?Reduced graphene oxide/Bi₂₄O₃₁Br₁₀ composites with different loading ratios were prepared by one-step solvothermal method.The results of DRS,PL and EIS measurements show that graphene not only improves the photocatalytic absorptivity of the catalyst,but also acts as an excellent electronic conductor and carrier to increase the carrier separation rate and effectively inhibit the recombination of photogenerated electron pairs.Thus,the performances of reduced graphene oxide/Bi₂₄O₃₁Br₁₀composites in degradation of RhB solution under visible light and photocatalytic reduction of CO₂ under simulated solar irradiation are superior to that of pure Bi24O31Br10.In this study,the effects of different preparation methods on photocatalytic activity of Bi₂₄O₃₁Br₁₀ were discussed.Up-conversion phosphor/Bi₂₄O₃₁Br₁₀ and reduced graphene oxide/Bi₂₄O₃₁Br₁₀ composites were prepared respectively.The light response range of Bi₂₄O₃₁Br₁₀ was successfully extended to near infrared region and the carrier recombination efficiency was reduced respectively,which provided a powerful guidance for the preparation and modification of photocatalysts in the future.