Study On The Catalytic Mechanism And Structure-activity Relationship Of Mxene Supported Single/Bimetalic Atom Catalysts For CO₂ Reducction Reaction To C₁/C₂ Products

Electrochemistry is an effective method to reduce carbon dioxide into high value-added fuels or chemicals,which is expected to alleviate energy shortage and environmental pollution problems related to"greenhouse effect".Among them,high performance electrocatalyst is the key of CO₂gas recovery and utilization.Atomically dispersed electrocatalysts have high theoretical atom utilization rate（100%）,flexible coordination environment and electronic structure,and high catalytic activity.Therefore,in this paper,we mainly designed and constructed atom-dispersed single/bimetallic atom catalysts anchored on MXene structure,and utilized density functional theory（DFT）calculation based on first principle to explore the relationship between the microstructure of single/bimetallic atom catalysts and the selectivity of reaction products and catalytic activity.The main contents include:（1）Research on electrocatalytic CO₂RR on MXene supported single metal atom.The single transition metal（TM）was anchored on the Mo₂CO₂structure to form TM-SACs（TM=Sc,Ti,V,Cr,Mn,Fe,Co,Ni,Cu,Zn）.By DFT calculation,the possible reaction paths and related intermediates for the formation of C₁ products from CO₂RR on the constructed TM-SACs were explored.The results showed that due to the weak adsorption strength of*OCHO intermediates on the surface of TM-SACs,the product selectivity of CO₂RR to HCOOH was very high.Among them,The Zn-SAC structure itself can well inhibit HER,and the electrocatalytic CO₂RR to HCOOH product has a low limiting potential U_L=-0.35 V,so it has excellent catalytic performance of CO₂RR.Author also proposed a structural descriptorφ=（Tb-Tm）×N/（E1×Eele）,to characterize the electrocatalytic performance of CO₂RR to HCOOH product on TM-SACs.The relationship between the descriptor and the limiting potential is volcanic,and Zn-SAC near the volcano peak has the best electrocatalytic performance.（2）Research on electrocatalytic CO₂RR on MXene supported bimetal atoms.A series of mono-dispersed bimetallic atom catalysts were designed to anchor two adjacent transition metal（TM）atoms on the Mo₂CO₂structure to form CuTM-BACs（TM=Fe,Co,Ni,Cu,Zn）.By means of DFT calculation,the most comprehensive reaction path and related intermediates for electrocatalytic CO₂RR to C₁ and C₂ products on CuTM-BACs have been explored.The results show that CuFe-BAC has the highest catalytic performance for the reduction of CO₂ to C₂H₅OH（U_L（C₂H₅OH）=-0.44 V）,and CuNi-BAC has the best catalytic performance for CH₄（U_L（CH₄）=-0.46 V）.Finally,Author propose an intrinsic descriptorφ=N×Eele×Ecoh,including the numbers of d electron（N）,electronegativity（Eele）and cohesive energy（Ecoh）,to characterize the electrocatalytic performance of CO₂RR to C₂H₅OH on CuTM-BACs.The relationship betweenφand limiting potential U_L is volcanic,and CuFe-BAC near the volcano peak has the best electrocatalytic performance.At the same time,φcan also be divided into CO₂RR product types in different regions:（1）whenφ<53.5,C₂H₅OH and CH₄ products are generated simultaneously;（2）When 53.5<φ<62.6,C₂H₅OH was generated;（3）When 62.6<φ<67.2,H₂ is generated;（4）Whenφ>67.2,CH₄products are generated.The results show that the atomic catalyst has good catalytic performance for CO₂RR.In addition,the mechanism of MXene supported single/bimetal atom electrocatalytic CO₂RR reaction has been deeply understood.At the same time,the proposed structure descriptors can well characterize the catalytic selectivity and activity of the catalytic system for electrocatalytic reduction of CO₂,so as to effectively screen and predict this kind of catalyst.This work provides theoretical guidance for the study of highly selective and highly active CO₂RR electrocatalysts.