Preparation And Function Of BiO_2-x Based Heterostructure Photocatalysts

There are many kinds of photocatalysts in bismuth-based photocatalysts,and their preparation,characterization,catalytic performance test and mechanism research have achieved rapid development.Among,the overlap between the 6s and O 2p orbitals of Bi³⁺ions in the trivalent bismuth group（III）semiconductor can narrow the forbidden band width and broaden the valence band width,which is beneficial to the improvement of photocatalytic performance.Besides,the empty 6s orbital of Bi⁵⁺in Bismuth（Ⅴ）-based compounds could also modify the band gap and support the high photocatalytic activity.Recently,BiO_2-x-x has attracted extensive attention from researchers due to its unique mixed valence state,suitable band gap width and good photocatalytic activity.However,limited by the optical carrier recombination efficiency and the stability of photocatalyst,the photocatalytic activity of BiO_2-x-x still has defects,and it is urgent to conduct in-depth and systematic research on how to improve the separation of carriers and the stability of photocatalyst.Based on these,the studies in this thesis mainly focus on the basis of BiO_2-x-x to improve photocatalytic activity by constructing heterogeneous junctions,and the relevant contents are listed as follow:（1）The effect of the addition amount of NaOH on the preparation of BiO_2-x-x photocatalyst was investigated by hydrothermal synthesis.Studies have shown that the optimum preparation conditions for BiO_2-x-x when the concentration of NaOH in the reaction system is 1M.The prepared BiO_2-x-x has good crystallinity and considerable photocatalytic activity.（2）BiOCl/BiO_2-x-x heterostructure photocatalyst was constructed with BiOCl as the second phase by using the method of liquid self-assembly synthesis.The optimal composite ratio was studied and the photocatalytic performance mechanism was further discussed.The results show that when the mass ratio of the composite BiOCl was 10%,the degradation efficiency of the obtained material on MO reaches the maximum.The reason for the increase of photocatalytic activity is mainly attributed to the cross-state of both BiOCl and BiO_2-x,which promotes the effective separation and migration of photogenic carriers.（3）The effect of NaOH content on the preparation of NaBiO₃/BiO_2-x-x heterostructure photocatalyst was investigated by hydrothermal synthesis.The degradation of methyl orange（MO）by the obtained material under visible light irradiation not only shows good photocatalytic activity,but also shows a strong"memory"effect after illumination,enabling it to remove organic pollutants in the dark.It promotes the practical application of photocatalysts in degrading organic pollutants.（4）The TiO₂/BiO_2-x-x heterostructure was constructed with TiO₂ as the second phase by hydrolysis method,and the mechanism of photocatalytic activity was discussed.By degrading MO under visible light and photocatalytic hydrogen production,it was found that when the mass ratio of the composite TiO₂ was 10%,the catalytic performance of the obtained material reached a maximum.PL and EIS measurements show that the photogenerated carriers can be effectively separated and transferred,which is conducive to the improvement of photocatalytic activity.