Preparation Of Halide Perovskite Catalyst And Study On The Performance Of Photocatalytic For CO₂ Reduction

In order to dealing with global warming,and achieving carbon neutralization goal,it is special important to strengthen the research and application of green and low-carbon technology.Artificial photosynthesis,which is driven by inexhaustible solar energy and can be used to convert CO₂ into high value-added carbon chemicals,has become the focus of current research.In this context,halide perovskite materials（PVK）are considered as one of the most competitive photocatalysts for CO₂ reduction due to their excellent photoelectric properties,simple preparation process,high catalytic activity and controllable composition.However,with the gradual exploration of PVK in the field of artificial photosynthesis,some problems hindering its practical application,such as poor catalytic stability,lack of active sites on the surface and poor selectivity of reduction products,have emerged.In order to solve these problems,we proposed some strategies to improve the photocatalytic activity,including:in situ construction of homogeneous perovskite nanosheets to improve catalytic stability,embedding PVK into metal-organic framework to increase surface active sites and enhance CO₂ pre-adsorption,sharing atoms with metal-organic framework to form charge transfer channels to promote photo-generated carrier separation,reducing the energy required for the reaction rate limiting step and improving the selectivity of the reduction products.The research contents are as follows:1.A novel perovskite-based catalyst via in situ growing of 2D Cs Pb₂Br₅nanosheets on the surface of Cs Pb Br₃ quantum dots（QDs）for CO₂ photo-conversion have been developed.Cs Pb Br₃ QDs were generated by peeling off layers from their cubic counterpart meanwhile Cs Pb₂Br₅nanosheets were formed by heaping up the peeled layers.The resultant dual phase composite exhibited outstanding activity and selectivity for photocatalytic conversion of gaseous CO₂ by a CO generation rate of197.11μmol g^-1 h^-1 under 300 W Xe lamp irradiation,which is 2.5 and 1.1 times than that of pure Cs Pb₂Br₅ and Cs Pb Br₃.Importantly,compared with Cs Pb Br₃,the fabricated dual phase material presents extremely high stability which can maintain unchangeable CO generation rate under consecutive ten hours of the recycling test.Further,attributing to the in situ assembling strategy between Cs Pb Br₃ and Cs Pb₂Br₅,the close contact allows photo-generated electrons in Cs Pb Br₃ QDs to transfer rapidly into Cs Pb₂Br₅ and the affluent active sites in such architecture enable to enhance CO₂photo-conversion activity.This work provides an attractive approach for in situ constructing the consubstantial perovskite-based composite photocatalyst to ensure the great stability and excellent activity for artificial photocatalytic CO₂ conversion.2.Cs₂Ag Bi Br₆ quantum dots（QDs）were embedded into the Ce-Ui O-66-H metal-organic framework,and a close contact interface was constructed between the two components.Benefiting from the photocatalytic properties and high adsorption capacity for CO₂,the optimized 20Cs₂Ag Bi Br₆/Ce-Ui O-66-H adsorption-photocatalyst exhibits outstanding performance for reductive CO₂ deoxygenation with considerable CO generation rate(309.01μmol g^-1 h^-1)under simulated solar light irradiation with300 W Xe lamp,which is about 2.1 and 2.7 times than that of pure Cs₂Ag Bi Br₆ and Ce-Ui O-66-H,respectively.The excellent catalytic conversion of CO₂ is ascribed to the effective solar harvest and quickly photo-excited carriers’separation in such assembled architecture.Importantly,due to the in-situ synthesis,Cs₂Ag Bi Br₆ QDs are intercalated in the Ce-Ui O-66-H frameworks and it could lead to improved stability and induce abundant oxygen vacancies in Cs₂Ag Bi Br₆/Ce-Ui O-66-H,which can maintain unchangeable CO generation rate under consecutive ten hours of the recycling test.This work provides great potential for the combination of metal-organic framework and lead-free halide perovskite to artificially photocatalytic CO₂ conversion to CO under mild gas-solid reaction conditions.3.The novel Cs₃Bi₂Br₉/Bi-MOF composite was prepared via in situ growing strategy of Cs₃Bi₂Br₉quantum dots on the surface of Bi-MOF nanosheets through the co-shared bismuth atoms.The prepared Cs₃Bi₂Br₉/Bi-MOF exhibits bifunctional merits for both high capture and effective conversion of CO₂,among which the optimized 3Cs₃Bi₂Br₉/Bi-MOF sample shows a CO₂-CO conversion yield as high as572.24μmol·g^-1·h^-1 under 300 W Xe lamp irradiation.The mechanism investigation uncovers that the intimate atomic-level contact between Cs₃Bi₂Br₉ and Bi-MOF via the co-shared atoms not only improves the dispersion of Cs₃Bi₂Br₉ QDs over Bi-MOF nanosheets but also accelerates interfacial charge transfer by forming a strong bonding linkage,which makes it have the best performance of CO₂ photoreduction.This work provides great potential for the combination of metal-organic framework and lead-free halide perovskite to artificially photocatalytic CO₂ conversion to CO under mild gas-solid reaction conditions.4.Cs₃Bi₂Br₉ quantum dots（QDs）are encapsulated in Bi OBr nanosheets by adding trace amounts of water.We used In-situ FTIR to monitor the active site and reaction intermediates on the catalyst surface.Combined with DFT calculation,it was found that bicarbonate（HCO₃*）and carboxylate（COOH*）are the main intermediates in the CO₂ reduction process on the surface of Cs₃Bi₂Br₉ QDs/Bi OBr.CO₂ is photoreduced to CO through the dual reduction path of HCO₃*and COOH*intermediates,thus effectively improving the selectivity of CO₂ reduction products.In addition,the in-situ growth makes the shared Bi-Br bond between Cs₃Bi₂Br₉ and Bi OBr exist.By the shared Bi-Br bonding linkage,the smoothly tunnels are constructed to quickly transport photo-generated carriers.Therefore,the Cs₃Bi₂Br₉/Bi OBr exhibits the highest CO₂-to-CO conversion efficiency generating 289.56μmol g^-1 h^-1 of CO yield with 98.7%selectivity under 300W Xe lamp illumination.This work provides a new strategy for constructing heterojunction in situ to prepare highly efficient and selective photocatalysts.