Study On Preparation And Photodegradation Of Bi₁₂O₁₇Cl₂-based Composites

Semiconductor photocatalysis is one of the most prospective ways for disposing the degradation of organic-pollutant and settling energy crisis.As a material,Bi₁₂O₁₇Cl₂ has excellent photocatalytic performance and stability.Nonetheless,the practical application of Bi₁₂O₁₇Cl₂ is impeded by the fast recombination speed of charge.Therefore,it is necessary to effectively modify Bi₁₂O₁₇Cl₂ and exploit Bi₁₂O₁₇Cl₂-based material with high activity.In this paper,two different types of composite photocatalysts were designed and synthesized by hydrothermal way and impregnation way respectively,such as the binary composite photocatalyst Co₃O₄/Bi₁₂O₁₇Cl₂ and Transition metal doped composite semiconductor material Ni（Co,Cd,Zn）/Bi₁₂O₁₇Cl₂,and carried out a variety of characterization.The photocatalytic performance of the made material was evaluated via degrading multifarious pollutants.The contents are as follows:（1）The Co₃O₄/Bi₁₂O₁₇Cl₂ heterojunction composite photocatalysts with different proportions of Co₃O₄ were prepared by one-pot hydrothermal course.A series of characterization and analysis are implemented,and the results show that the Co₃O₄ nanoparticles with cube-sugar evenly distributed on the surface of Bi₁₂O₁₇Cl₂ nanosheets.The formation of heterostructure between Bi₁₂O₁₇Cl₂ and Co₃O₄ in the system not only improves the light trapping ability of the composite material availably,but accelerates the separation efficiency of photoinduced charge carriers.The results manifested that Co₃O₄/Bi₁₂O₁₇Cl₂ sample displays the highest photocatalytic ability when the mass of Co₃O₄ is 10 mg.It is proved that Co₃O₄/Bi₁₂O₁₇Cl₂composite has good cyclic stability thyough cyclic experiments.In addition,the photocatalytic performance of Co₃O₄/Bi₁₂O₁₇Cl₂photocatalyst was tested by electrochemical workstation.According to the results of trapping experiment and electron spin resonance,the free radicals including hole（h⁺）and superoxide free radicals（·O₂^-）in the degradation of Rh B,and the photocatalytic reaction mechanism was analyzed.（2）A novel metal Ni（Co,Cd,Zn）doped Bi₁₂O₁₇Cl₂ composite semiconductor photoatalyst(Ni/Bi₁₂O₁₇Cl₂,Co/Bi₁₂O₁₇Cl₂,Cd/Bi₁₂O₁₇Cl₂and Zn/Bi₁₂O₁₇Cl₂)was prepared by impregnation method.Under the simulated visible light irradiation,the ability of Bi₁₂O₁₇Cl₂doped with different metals for the degradation of Rh B and MB was studied.The experimental results discovered that composites showed better photodegradation ability than pure Bi₁₂O₁₇Cl₂,and Ni/Bi₁₂O₁₇Cl₂-2composite displays the highest photodegradation ability.Moreover,the separation efficiency of photo-generated e^-/h⁺pairs was studied by transient photocurrent tests.Cyclic experiments indicated that the composites have reusability.Based on the results of trapping experiment,it is uncovered that h⁺and·O₂^-were the dominating free radicals for the degradation of Rh B,and the photocatalytic degradation mechanism was analyzed.