Preparation And Properties Of Bi₂O₄ Based Heterojunction Photocatalytic Materials

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,Bi₂O₄ has attracted great research interest owing to its unique mixed valence state,suitable band gap and good photocatalytic activity.However,limited by the optical carrier recombination efficiency,the photocatalytic activity of Bi₂O₄ is not particularly outstanding.It is urgent to make a thorough and systematic study on how to improve its photocatalytic activity and the separation of carriers.Based on these,the studies in this thesis mainly focus on the fabrication of Bi₂O₄ to build a heterojunction,and the relevant contents are listed as following:?1?NaBiO₃/Bi₂O₄ photocatalysts were prepared by a hydrothermal method.In order to determine the optimum synthesis conditions,the synthetic process were studied and and the performance of the sample was tested.The results showed that NaBiO₃/Bi₂O₄ prepared by hydrothermal 2.5h,which have the best degradation effect and good chemical stability to MO under visible light,and pure Bi₂O₄ phase can be obtained with 180?for 6h.?2?g-C₃N₄/Bi₂O₄ heterojunction was constructed by the hydrothermal method with g-C₃N₄ as the second phase.The performance of Bi₂O₄ was regulated by g-C₃N₄and the optimum compound ratio was studied,and the mechanism of photocatalytic performance was discussed in depth.The research shows that g-C₃N₄ and Bi₂O₄ can intercross each other,which can promote the effective separation and migration of photogenerated carriers.When the mass ratio of g-C₃N₄ is 10%,the obtained material has the highest photocatalytic activity.?3?The Bi₂O₄/BiOBr heterojunction was constructed in situ with BiOBr as the second phase by chemical etching,and its mechanism of promoting photocatalytic activity was discussed.The research shows that the in situ reaction of Bi OBr by Bi₂O₄can greatly improve the photocatalytic activity and chemical stability of the materials.When the compound BiOBr molar ratio reaches 33.3%,the degradation efficiency of the material to RhB and MO reaches the maximum.The photocatalytic mechanism is effective separation and migration of photogenerated carriers..