Preparation And Photocatalytic Performance Of Bimetal Bromide Perovskite And Its Complex

The problem of water pollution caused by pollutants such as antibiotics and dyes is a major problem to be solved urgently in environmental pollution control today.Semiconductor photocatalysis technology has been considered as one of the best way to alleviatethe above issues due to its high efficiency and no secondary pollution.At present,metal lead halide perovskites have a large number of applications in photoelectric conversion.However,the Pb element in metal lead halide perovskites has heavy metal toxicity;what’s more,its ionic properties induced phase transformation make it unstable in water system.These two disadvantages limit its application in the field of photocatalytic degradation.Therefore,the aims of this paper is to reduce the content of Pb and improve the water stability of bimetal bromide perovskite.Sn-doped CsPb_xSn_1-xBr₃ with reduced content of Pb was prepared,and its performance in photocatalytic degradation of antibiotics in organic systems was tested.Further,Ag,Bi bimetallic lead-free perovskite Cs₂AgBiBr₆ was prepared Quantum dots（QDs）and its performance in photocatalytic degradation of antibiotics in organic systems were evaluated.Finally,a water-stable Cs₂AgBiBr₆-TiO₂ heterojunction was constructed by coating with nano-TiO₂ and its photocatalytic degradation of antibiotics in water was studied.Details are as follows:（1）CsPb_xSn_1-xBr₃ bimetallic bromide perovskites were synthesized by antisolvent precipitation.The morphology,structure and surface state of the CsPb_xSn_1-xBr₃ bimetallic bromide perovskite were characterized by SEM,TEM,XPS and so on;the active species and its visible light catalytic degradation of tetracycline hydrochloride（TC-HCl）reaction mechanism were studied by trapping experiments.The results show that Sn elememt successfully replaces part of Pb element.it not only reduced the bulk toxicity of Pb-based perovskites,but also improved the photodegradation efficiency of TC-HCl.The successfully prepared of Sn-doped CsPb_xSn_1-xBr₃ and applied in photodegradation of TC-HCl made it possible for the direct application of metal halide perovskites to antibiotic pollution control in life.（2）Cs₂AgBiBr₆ QDs were successfully prepared by hot injection method,and its structural and morphological characterizations and visible light catalytic performance tests were carried out via XRD,TEM and SEM.Rhodamine B（Rh B）,methyl orange（MO）and TC-HCl have been used as model pollutants.The degradation rate of these pollutants are 100%,90%and 50%,separately when using 20 mg Cs₂AgBiBr₆ QDs within 30 minutes.Capture experiments found that superoxide radicals（·O₂^-）and holes（h⁺）were the main active species for photocatalytic degradation.This experiment provides a new application of lead-free bimetallic bromide perovskites in organic systems.（3）Cs₂AgBiBr₆-TiO₂ nanocomposites were successfully prepared by hot injection and solvothermal methods.The stability test proves that the Cs₂AgBiBr₆-TiO₂nanocomposite has good stability in water and can efficiently degrade TC-HCl in water,and its optimal degradation rate is 25 times than that of commercial TiO₂（P25）.The trapping experiments confirmed that the main active species in the photocatalytic reaction were superoxide radicals and holes,and a Z-type heterojunction reaction mechanism was proposed.This experiment provides an experimental basis for the construction of stable bimetallic bromide perovskites in water and their application in environmental governance.