Photocatalytic Activity Of Doped And Composite System Based On Double Perovskite Cs₂AgBiCl₆

In recent years,the environmental crisis caused by organic dyes has become increasingly serious.Therefore,harmless treatment of organic dyes is very important.Photocatalysis is considered as an efficient,green and sustainable treatment method of organic dye.Photocatalysts have been widely studied due to their important roles in this process.However,the common photocatalyst,such as metal oxides,metal sulfides,and metal organic frameworks,either has low solar energy utilization or high recombination rate of photogenerated carriers,which seriously restricts the further application.Therefore,looking for new and highly efficient photocatalyst has been one of the hot spots of this research.Studies have shown that metal halide double perovskite has the advantages of high light absorption,excellent carrier mobility,tunable band structure and low toxicity,which may be an ideal high-efficiency photocatalyst.In this paper,the photocatalytic performance of metal halide double perovskite Cs₂AgBiCl₆ with visible light absorption was studied.Subsequently,Br was used to replace Cl and Cs₂AgBiCl₆/Bi₂WO₆ composite system was constructed to explore the improvement of its photocatalytic performance.Details are as follows:1.Cs₂AgBiCl₆ particles were prepared by hydrochloric acid precipitation method and anti-solvent recrystallization method,respectively.The grain size of Cs₂AgBiCl₆synthesized by anti-solvent recrystallization method was small,about 100～300 nm,and the sample synthesized by hydrochloric acid precipitation method was about 1～5μm.Under the irradiation of 300 W Xe lamp（equipped with 400 nm cut-off filter）,Cs₂AgBiCl₆ prepared by anti-solvent recrystallization method can degrade 95.7%Sudan III within 10 min,and has good cycle stability,while Cs₂AgBiCl₆ prepared by hydrochloric acid precipitation method can only degrade 15.4%Sudan III.The sample synthesized by anti-solvent recrystallization has small size and large specific surface area,which may provide more reactive sites and lead to high photocatalytic efficiency.In addition,Cs₂AgBiCl₆ can also efficiently degrade Methyl red（35 min,96%）and Malachite green（5 min,99.99%）,indicating that Cs₂AgBiCl₆ has excellent photocatalytic performance.2.Cs₂Ag Bi Cl_6-xBr_x with different Br contents was prepared by adding Br source in precursor solution and using antisolvent recrystallization method.When x=2,99.9%methyl red can be degraded within 35 min under 300 W xenon lamp（equipped with400 nm cut-off filter）,and the kinetic constant is 2.25 times higher than that of Cs₂AgBiCl₆.The results showed that the photocatalytic performance of Cs₂AgBiCl₆was improved.It was possible that the band gap of Cs₂AgBiCl₆ was reduced due to the introduction of Br,which effectively widened the light response range of Cs₂AgBiCl₆.3.Cs₂AgBiCl₆/Bi₂WO₆ composite system was synthesized.Compared with Cs₂AgBiCl₆ and Bi₂WO₆,Cs₂AgBiCl₆/Bi₂WO₆ shows the best photocatalytic performance,and its kinetic constants are 1.18 times and 31 times of Cs₂AgBiCl₆ and Bi₂WO₆,respectively.At the same time,Cs₂AgBiCl₆/Bi₂WO₆ has good cycle stability.The construction of Cs₂AgBiCl₆/Bi₂WO₆ heterojunction improves the photogenerated carrier separation efficiency of Cs₂AgBiCl₆,thereby improving its photocatalytic performance.