Novel Bi₂₄O₃₁Br₁₀ Visible-Light-Driven Photocatalyst: Preparation,Characterization And Modification

With the continuous development of industrialization and the rapid growth of the population,water pollution has become an increasingly serious problem.Semiconductor photocatalytsis is considered to be one of the most promising solutions to water pollution problems.As a novel visible light photocatalyst,Bi₂₄O₃₁Br₁₀ has attracted great research interest owing to its unique layered structure,suitable band gap and high chemical stability.Nonetheless,the activity of Bi₂₄O₃₁Br₁₀ is greatly limited by the narrow visible light response range and high recombination of photogenerated electron-hole pairs.There remains an urgent need for a series of in-depth and systematic studies on how to enhance its photocatalytic activity.Based on these,the studies in this thesis mainly focus on the fabrication and modification of Bi₂₄O₃₁Br₁₀ and the relavent contents are listed as following:?1?Bi₂₄O₃₁Br₁₀ photocatalysts were prepared by a solvothermal method,and systematical studies were carried out to determine the optimum parameters.The results showed that pure Bi₂₄O₃₁Br₁₀ phase can be obtained with 6 ml NaOH solution?2 M?used,which can effectively degrade RhB under visible light irradiation.?2?Bi₂₄O₃₁Br₁₀ microstructures were precisely modulated by using soluble starch as surfactant.The relationship between microstructure and photocatalytic activity was detailed studied.It was found that starch played a key role in shaping morphology of Bi₂₄O₃₁Br₁₀,and especially a novel grain-like Bi₂₄O₃₁Br₁₀ hierarchical architecture could be obtained by adding the right amount of starch.Such unique hierarchical architectures not only resulted in higher specific surface area,stronger photoabsorption in the visible light region but also helped to separate photogenerated electrons and holes,which greatly improve the photocatalytic activity.?3?Er-doped Bi₂₄O₃₁Br₁₀ samples were successfully prepared via the solvothermal method and the mechanism of enhanced photocatalytic activity was studied systematically.The results showed that Er dopant has little effect on the crystal structure of Bi₂₄O₃₁Br₁₀.However,Er dopant induced a significant improvement in the photocatalytic activity.1.0%Er-Bi₂₄O₃₁Br₁₀ sample presented the best photocatalytic performance.The enhanced activity was attributed to the effective trapping of photogenerated electron by Er3+ ion and the up-conversion process resulting from Er dopant.?4?Based on the above researches,we modulated the microstructure of Bi₂₄O₃₁Br₁₀ accompanied by Er doping in order to explore whether there is a certain synergistic effect between them.The results showed that Er dopant had certain influence on the microstructure modification of Bi₂₄O₃₁Br₁₀ via the soluble starch,which was not conducive to the formation of grain-like Bi₂₄O₃₁Br₁₀ hierarchical architecture.The degradation of RhB showed that the photocatalytic activity of as-prepared samples was not significantly improved,indicating that there was no positive synergistic effect between the two measures.And the further researches need to be carried out in the future.