Study On The Preparation And Photocatalytic CO₂ Reduction Performance Of 2D Halide Perovskite Based Heterojunction

With the rapid growth of the world population and the continuous expansion of industrialization,the overconsumption of traditional fossil energy has not only created an energy problem,but also brought forth a series of environmental problems due to the emission of a large amount of CO₂ and other greenhouse gases.Using solar energy to reduce CO₂ into high value-added fuels or chemicals,artificial photosynthesis is not only helpful to solve the serious problem of fossil fuel consumption,but also coincides with the national“double carbon”strategy.At present,the development of high-efficiency and low-cost artificial photosynthesis catalyst is crucial to move forward with the commercialization of this technology.In recent years,halide perovskite materials have become a kind of potential photocatalyst materials because of their low cost,high absorption coefficient,easily regulated energy band structure,long carrier lifetime and so on,which have received extensive attention in the field of artificial photosynthesis.So as to enhance the activity of photocatalytic CO₂ of these materials,this thesis focuses on the construction of two-dimensional halide perovskite heterojunctions and the regulation of interfacial charge transfer kinetics,and the following two works are carried out:（1）Firstly,we used a simple lattice matching growth method to in situ grow CsPbBr₃ nanosheets on the surface of pre-synthesized perovskite material SrTiO₃nanosheets to prepare a series of SrTiO₃/CsPbBr₃ composites,which were used as photocatalysts for CO₂ reduction.Thermodynamic and charge-transfer kinetic studies shown that the interface between SrTiO₃ and CsPbBr₃ forms a type-II heterojunction,and the photogenerated electrons in CsPbBr₃ can be rapidly transferred to the conduction band of SrTiO₃,while the photogenerated holes in SrTiO₃ can be rapidly transferred to the valence band of CsPbBr₃,thus achieving an effective spatial separation of photogenerated charges.The SrTiO₃/CsPbBr₃ heterojunction photocatalyst achieves a high yield of 65.5±3.4μmol g^-1 h^-1 for CO₂-to-CO conversion,which is about 5.4 and 3.6 times higher than those of individual SrTiO₃ and CsPbBr₃ nanosheets,respectively.（2）Considering that strontium elements are easily precipitated on the surface of SrTiO₃ nanosheets to form strontium oxides or hydroxides,a series of composite photocatalysts of T-SrTiO₃/CsPbBr₃ for CO₂ reduction were prepared by etching SrTiO₃ with NH₄F to make its capped with Ti-O bonds before growing CsPbBr₃nanosheets in situ.It was shown that the interfacial charge transfer rate between SrTiO₃nanosheets and CsPbBr₃ was significantly accelerated after NH₄F etching treatment relative to the untreated SrTiO₃ nanosheets,which further improved the photogenerated charge separation efficiency between SrTiO₃ nanosheets and CsPbBr₃.Therefore,the T-SrTiO₃/CsPbBr₃ composite exhibits an obviously improved photocatalytic CO₂reduction performance with a CO generation rate of 120.2±4.9μmol g^-1 h^-1 compared to that(65.5±3.4μmol g^-1 h^-1)of SrTiO₃/CsPbBr₃ heterojunction,which is also higher than those of other halide-perovskite-based materials reported in the literatures under the same conditions.