Construction Of Highly Efficient Heterojunction Composite Photocatalyst And Its CO₂ Reduction Researc

Excessive carbon dioxide（CO₂）emissions not only cause serious environmental crises but also impede the development of human society.Photocatalytic reduction technology can directly convert CO₂into high-value products,such as C₂H₅OH,enabling the green cycle of carbon resources.This process uses solar energy as a non-polluting energy source,and it does not consume excess energy,providing a new approach to solving environmental problems and energy crises simultaneously.Among all semiconducting materials,chalcogenide materials possess excellent photovoltaic properties and are widely applied in solar cell technology.The p-type semiconductor ZnTe has a highly negative conduction band position that can enhance electron transfer driving force.Therefore,these two materials show great potential in the CO₂reduction field.However,both chalcogenide materials and p-type semiconductor ZnTe suffer from serious issues of charge recombination and poor stability.Heterojunction engineering is the most effective method to promote electron-hole pair separation.This paper aims to address the problem of severe charge recombination by constructing type-II heterojunctions CsPbBr₃/CdSe and p-n type heterojunctions ZnTe/Cu-TCPP to promote charge transfer and separation,which is expected to improve the CO₂reduction performance of the catalysts.This thesis focuses on the following aspects:（1）The type-II CsPbBr₃/CdSe composite catalysts were constructed by in-situ growth of CdSe quantum dots on CsPbBr₃quantum dots.First,the successful preparation of the composite was demonstrated by elemental mapping and XRD,and the energy band structure was determined by UPS and UV-vis,confirming a typical type-II heterojunction.Secondly,a series of carrier kinetic characterizations such as PL,TRPL,EIS,and I-t were tested,and the results showed that the carrier lifetime of the composites became longer,the transfer resistance became smaller and the photocurrent became larger,indicating that the composites promoted the effective separation of charges,inhibited the charge complexation.Finally,the photocatalytic CO₂reduction performance of the composites was tested.Under the condition of no sacrificial agent,the photocatalytic CO₂reduction product CO yield of CsPbBr₃/CdSe was as high as 115.26 mmol g^-1,which was 4.6 times higher than that of CsPbBr₃alone.The charge difference density diagram and electron localization function indicate that the interface between CsPbBr₃and CdSe tends to form Pb-Se and Cd-Br bonds,which facilitates the charge transfer.The theoretical calculations combined with experiments provide an in-depth investigation of the reasons for the enhanced performance of the composite catalyst,which is a guideline for further research of chalcogenide photovoltaic materials in the field of photocatalytic CO₂.（2）The p-n type ZnTe/Cu-TCPP heterojunction composites were designed and synthesized.The successful preparation of the composites was demonstrated by elemental mapping and XRD.The formation of the built-in electric field in the p-n junction promotes the charge separation,which is further confirmed by PL,TRPL and electrochemical tests that show the composites facilitate charge transfer and separation.The robust benzene ring structure in Cu-TCPP facilitates the carrier transport and maintains the catalyst’s structure stability,and Cu-TCPP’s framework structure has better CO₂adsorption capacity than other nanoparticle catalysts.Meanwhile,the metal Cu in Cu-TCPP,as the main catalytic active center,can effectively activate CO₂,and the synergistic interaction between ZnTe and Cu-TCPP can efficiently convert CO₂to CO and CH₄.The photocatalytic CO₂reduction product CO of ZnTe/Cu-TCPP composite is 4.8 times higher than that of ZnTe alone.