Preparation And Photoreduction CO₂ Properties Of CsPbBr₃ QDs Composites

The photocatalytic CO₂ reduction process is becoming a promising strategy to solve a series of energy problems in recent years.Due to the excellent optics properties and suitable energy band structure,CsPbBr₃ quantum dots（QDs）have been wildly used in the photocatalytic process.However,the application of CsPbBr₃ QDs in the photocatalytic CO₂ reduction is still greatly restricted,owing to their rapid recombination of photoinduced electrons and holes.Herein,in this thesis,we synthesize Ti₃C₂/CsPbBr₃ QD composites and Bismuthene/CsPbBr₃ QD composites by in situ self-assembly and in situ growth method,respectively.We enhance the photocatalytic CO₂ reduction performance and stability by construction different heterojunction structure.The photocatalytic CO₂ reduction perfoemance are tested and analyzed.Additionally,we discuss the photoinduced electrons and holes transfer path and propose the possible photocatalytic mechanism.CsPbBr₃ QDs with excellent optical properties are synthesized via a typical thermal injection method.CsPbBr₃ QDs exhibit the average size of about 8 nm and show strong absorption in the range of UV light region with the absorption band edges of 530 nm.Bismuthene is prepared through a high energy ball milling process with binders（PVDF）and commercial bismuth.As a result,Bismuthene possesses an irregular sheetlike structure and the size is measured to be about 0.5-1.0μm.Additionally,Bismuthene exhibits excellent optical properties in the UV-Vis-Nir（300-2200 nm）region.In the present work,we prepare the Ti₃C₂/CsPbBr₃ QD composites by a self-assembly method.As a result,it is found that Ti₃C₂ is the typical transparent sheet-like material and CsPbBr₃ QDs are uniformly dispersed on the surface of Ti₃C₂ nanosheets.Photocatalytic CO₂ reduction result shows that Ti₃C₂/CsPbBr₃ QD composites exhibit the improved photocatalytic performance,which achieves 89.9μmol g^-1 for CO and96.5μmol g^-1 for CH₄.The selectivity of CH₄ for Ti₃C₂/CsPbBr₃ QD composites is81.1%,and the yield of CO increases 4.2 times and 9.4 times compared with Ti₃C₂ and CsPbBr₃ QDs,respectively.After three consecutive recycling tests,the photocatalytic CO₂ reduction conversions to CH₄ and CO still remain 98.4 and 97.4%,respectively.The enhancement of the photocatalytic CO production yield may be ascribed to the the construction of II heterojunction,which is favor for the separation of photoinduced electrons and improvement the utilization of photoinduced electrons.Bismuthene/CsPbBr₃ QD composites with strong Cs-Bi interfacial interactions are prepared by in-situ growth method in this thesis.After 5 hours’irradiation,the CO and CH₄ yields of Bismuthene/CsPbBr₃ QD composites are 157.8 and 215.6μmol g^-1under the Xe light irradiation.Bismuthene/CsPbBr₃ QDs exhibit the highest yield of CH₄ product under UV-Vis light irradiation for 5 hours,and CH₄ selectivity of 84.5%is achieved.Compared with CsPbBr₃ QDs,Bismuthene/CsPbBr₃ QDs display the prolonged lifetime in the TRPL spectra,which is consist with S-scheme heterojunction with the pathway of charge transfer.The mechanism of photocatalytic CO₂ reduction shows that the improved photocatalytic performance is expected to be achieved,as the construction of S-scheme heterojunction may suppress the recombination of the photoinduced carriers.Additionally,coupled with Bismuthene can enlarge the light absorption.which is useful for improvement the photocatalytic performance.