First-principles Calculations On The Activation And Conversion Of CO₂ Over Single-atom Scale Cu Structure Stabilized On MoS₂/Ag（111）

In modern society,the burning of fossil energy emits a large amount of CO₂,causing global climate crises such as glacier melting and greenhouse effect,affecting human production and life.In recent years,efforts have been made to capture CO₂and reduce it into hydrocarbons that can be used by human beings in order to reduce the amount of CO₂ in the atmosphere and realize the carbon cycle.Since CO₂molecules are very stable,effective catalysts are needed for their conversion and utilization.Metal catalysts,especially Cu-based catalysts,have high catalytic efficiency for the reduction and conversion of CO₂ due to their low cost and easy preparation.Among many products generated by CO₂ reduction,methanol（CH₃OH）not only has the characteristics of clean combustion and high biodegradability,but also is the key raw material of some high-value downstream products.Therefore,the catalytic reduction of CO₂ to CH₃OH has attracted wide attention.In this paper,from the perspective of first-principles calculation,it is studied that the magic structure Cu₃can be stably adsorbed on the Mo S₂/Ag（111）heterostructure substrate to form stable Cu₃/Mo S₂/Ag（111）catalyst.By comparing and studying the two reaction paths of Cu₃/Mo S₂/Ag（111）catalytic hydrogenation of CO₂ to CH₃OH,the results show that CO₂ is more likely to hydrogenate to form CH₃OH through*HCOO pathway,and the reaction barrier of the decisive step is 0.96 e V.This study provides theoretical guidance for the preparation of stable supported Cu-based catalysts and the catalytic reduction of CO₂ in experiments.This paper is divided into the following chapters.Chapter 1,Introduction.We introduced the background knowledge of CO₂catalytic reduction and the types of commonly used catalysts,focuses on the progress and shortcomings of Cu-based catalysts in the catalytic reduction of CO₂ as well as the common improvement methods,and then introduces the advantages of the two-dimensional material Mo S₂ as the supporting material of metal catalysts.Chapter 2,we introduced the density functional theory,the calculation software used and the specific calculation details.Chapter 3,the main catalyst in this paper is introduced.By comparing and analyzing the energy second-order difference between Cu _N（Cu cluster）in the gas phase state and the adsorption on Mo S₂/Ag（111）heterojunction,it is found that Cu₃ is a magic number structure and can be stably adsorbed on the substrate.The electronic structure properties and charge transfer at the interface before and after adsorption are further analyzed.Finally,Cu₃/Mo S₂/Ag（111）catalyst was determined.Chapter 4,the reduction and conversion of CO₂ with Cu₃/Mo S₂/Ag（111）catalyst is introduced,the reaction path of CH₃OH generation is determined,and the potential barrier to be overcome in the reaction process is given.Firstly,the adsorption configuration of CO₂was studied.By comparing the changes of bond lengths and bond angles before and after adsorption,it was proved that CO₂molecules could be stably adsorbed and activated on this structure.Then,the adsorption and dissociation of H₂on the catalyst was studied.It was found that the dissociation barrier was only 0.37 e V,which proved that the catalyst had a good ability to dissociate H₂,and the H（*H）adsorbed on the catalyst obtained from dissociation could be used as the hydrogen source for subsequent hydrogenation reaction.At last,the reaction process of CO₂ to CH₃OH along*COOH and*HCOO was compared and analyzed.The calculation shows that CO₂ is more inclined to hydrogenation reduction along*COOH path,which is superior to*COOH path both from the perspective of kinetics and thermodynamics.The critical step potential barrier of reaction along*HCOO path is 0.96 e V.In addition,it was found that the co-adsorption behavior of*OH group and some intermediates on the catalyst can reduce the potential barrier of hydrogenation reaction.Chapter 5,summary and prospect.