Study On The Catalytic Performance Of CsPbBr₃,Cs₄PbBr₆ And Their Composites

The treatment of water pollution,especially the treatment of organic pollutants in water,is a worldwide problem.Photocatalysis technology is an efficient,safe and environment-friendly water pollution control method.After decades of development,there are still some problems that need to be solved urgently,such as low utilization of sunlight.The metal halide perovskite materials represented by lead halide perovskite have the characteristics of high light absorption coefficient,high carrier mobility,long charge diffusion length,wide and adjustable light absorption range,etc.It is a rookie who has been applied to the field of photocatalysis in recent years,and shows excellent photocatalytic performance and great development potential.Although the metal halide perovskite has good photocatalytic performance,it generally suffers from poor stability.In this paper,based on the most widely used CsPbBr₃ in halide perovskite photocatalysis research,CsPbBr₃ and Cs₄PbBr₆ are composited by a simple synthesis method to improve the stability of sample,and the photocatalytic performance of CsPbBr₃/Cs₄PbBr₆ composites is studied.A series of cesium lead bromide materials?CsPbBr₃,Cs₄PbBr₆,CsPbBr₃/Cs₄PbBr₆?were prepared,and the effects of the contents of CsPbBr₃ and Cs₄PbBr₆ on the catalytic performance and the influence of the synthesis method on the stability of the catalyst were investigated.Finally,an attempt was made to improve the stability of the material through adjusting the catalytic solvent environment and annealing.The details are as follows:First,CsPbBr₃/Cs₄PbBr₆?PbBr₂:CsBr=1:1?composites was synthesized directly by supersaturation recrystallization.Under the irradiation of 300 W xenon lamp,16mg of sample could degrade 84.2% methyl orange?MO?in aqueous solution within90 min.In the comparative experiment of photocatalytic degradation of MO,it was found that the sample could degrade 88.7%MO in 90 min under dark conditions;and22 mg of the same sample could degrade 91.1%MO in aqueous solution in 120 min.After 30 days of storage,the repeatibility of the catalytic performance of CsPbBr₃/Cs₄PbBr₆?PbBr₂:CsBr=1:1?was improved under light and dark conditions.In the process of catalytic or photocatalytic degradation of MO,?O₂^–played a major role.A series of cesium lead bromide materials?CsPbBr₃,Cs₄PbBr₆,CsPbBr₃/Cs₄PbBr₆?were synthesized by changing the molar ratio of lead bromide?PbBr₂?and cesium bromide?CsBr?.The catalytic performance increased with the increase of CsPbBr₃ content of samples under dark conditions.But the poor results of repeated test showed that the stability of samples was poor.These results may provide a new type of catalyst that can work simultaneously under light and dark conditions for the treatment of water pollutants.Secondly,in order to improve the water stability of the catalyst,a series of cesium lead bromine?CsPbBr₃,Cs₄PbBr₆,CsPbBr₃/Cs₄PbBr₆?were synthesized by water-assisted method.The result of catalytic performance test results showed that its catalytic degradation ability also increaseed with the increase of CsPbBr₃ content in the sample.CsPbBr₃ was the highest and the degradation efficiency was only 17.7%.Through comparison,in the process of water-phase catalytic degradation,the water stability of the water-assisted synthesis sample had improved.Finally,a series of samples synthesized by supersaturation recrystallization process were applied to photocatalytically degradation rhodamine B?RhB?in ethanol.1 mg CsPbBr₃ xenon lamp could degrade 97.7% of RhB in ethanol under 90 min,showing better photocatalytic performance than in water.In order to further improve the stability of CsPbBr₃,the samples were annealed in DMF atmosphere.After three cycles of photocatalytic test,the degradation efficiency of CsPbBr₃ was basically unchanged and was better than unannealed sample.And the XRD results of the samples before and after catalysis also showed that the samples had good stability.