First-principles Calculation Study Of Sc(Fe) Single Atom Catalyst Stabilized On The Surface Of Honeycomb Borophene/Al(111) Heterostructure

Theoretical design and experimental fabrication of highly efficient single-atom catalysts（SACs）containing isolated metal atoms monodispersed on appropriate substrates have surged to the forefront of heterogeneous catalysis in recent years.Nevertheless,the instability of SACs,i.e.,preferential clustering in the chemical reaction processes,dramatically hinders their practical applications.In this paper,using first-principles calculations,we predict that the honeycomb borophene/Al（111）heterostructure can be an ideal candidate to stabilize and enhance the catalysis of many transition metal（TM）SACs via a dual charge transfer mechanism.The Al（111）substrate donates electrons to the pre-covered two-dimensional honeycomb borophene（h-B）to stabilize the latter,and the deposited TM atoms further provide electrons to the h-B,enhancing the covalent binding between the h-B and the Al（111）substrate.Intriguingly,during the CO oxidation,the h-B/Al（111）heterostructure can in turn serve as an efficient electron reservoir to accept electrons from or donate electrons to the deposited TM-SACs and the reactants.Such a flexible dual charge transfer mechanism not only facilitates in stabilizing the TM-SACs rather than clustering,but also effectively reduces the reaction barriers.Particularly,contrast to expensive noble metal atoms such as Pd and Pt,low-cost Sc-and Fe-SACs are found to be the most promising SAC candidates that can be stabilized on h-B/Al（111）for O₂ activation and CO oxidation,with fairly low reaction barriers（around 0.48-0.65 e V）.The present findings may provide important theoretical guidance for experimental fabrication of highly stable,efficient,and economic SACs stabilized on various heterostructure substrates.This article expands the specific narrative through the following chapters:Chapter 1 is the introduction section,we briefly introduce the background knowledge related to the field of catalysis and the current popular catalyst-single atom catalyst,including the research progress,characterization technology,preparation method,single atom active site geometry and electronic structure stability on the substrate.The advances of single-atom catalysts in terms of catalytic performance are briefly described.In addition,the development prospects and challenges of single-atom catalysts in this field are also discussed.Chapter 2,theory and methods part,we mainly introduce the first-principles calculation method based on density functional theory and the setting of related parameters used in the calculation simulation in this thesis.In chapter 3,we first modeled the two-dimensional honeycomb h-B/Al（111）heterojunction system and found that each B atom obtained 0.68 electron from the Al（111）substrate,which is stable for electron-deficient the honeycomb borophene structure is crucial.Next,a series of transition metal atoms（TM）are deposited on the h-B/Al（111）system,including Sc,Ti,V,Cr,Mn,Fe,Co,Ni,Cu,Pd,Ag,Pt,and Au,to determine their stability in SAC formation.Bader charge analysis showed that these TM atoms all transferred part of their charge to the h-B/Al（111）heterojunction.Here,compared with the graphene system,it was found that the system can exhibit stronger metal substrate interaction（EMSI）.Next,by confirming kinetic（diffusion barrier）and thermodynamic stability（molecular dynamics）performance,it was found that relatively inexpensive TM（Sc and Fe）can be dispersed in a single h-B/Al（111）heterojunction in a highly dispersed single Atomic form exists.Therefore,it is hoped that the catalyst system can show high activity and high efficiency in the catalytic process.In chapter 4,based on the screening of excellent single-atom catalyst system in Chapter 3,the kinetic process of CO oxidation by Sc（Fe）-SACs catalyst was further simulated.First,the density of states（DOS）analysis of the single atom system showed that the single atom presented higher activity.Next,before the CO oxidation,the reactants（CO and O₂）were adsorbed to the system.Our study found that in both systems,the adsorption energy of O₂ is greater than that of CO,and the O-O bond is obviously elongated,indicating that the O₂ molecule has been significantly excited.This was confirmed in the subsequent CO oxidation process（low reaction barrier:0.48～0.65 e V）.Based on the discussion of the catalytic reaction mechanism,this thesis proves the dual charge transfer process by analyzing the evolution of charge transfer in the key steps in the CO oxidation process.That is,the current h-B/Al（111）heterostructure can serve as an attractive electron library,accepting electrons from the reactant to the deposited TM-SAC or donating electrons to the reactant,effectively stabilizing the deposited single atoms,thus Dominates the high catalytic performance of TM-SACs system.In chapter 5,we make a brief summary of this work and look forward to the future work.In this thesis,through the cooperative charge transfer mechanism,the kinetic process of the oxidation of CO by the non-noble metal atom Sc and Fe single atom catalyst system is explored,and the microscopic mechanism of charge transfer during the catalytic reaction is clarified.Moreover,the reaction barrier of CO oxidation is significantly lower than that of some experimentally typical noble metal single atom catalysts.Therefore,it is hoped that the current theoretical research can provide important research value and information for the experiment.