Theoretical Study On The Stability And ORR Activity Of Bi-atom Catalysts Based On Nitrogen-doped Graphene Supported

Atomically Dispersed bi-atom catalysts(BACs)exhibit remarkable catalytic performance in electrocatalysis reactions especially oxygen reduction reaction(ORR),due to the adjacent and coordination-unsaturated metal active sites and interatomic synergistic effect.However,so far most research primarily focus on screening on BACs with outstanding catalytic activity for specific reactions,while rare effort on a theoretical level has spent on examining the stability of the BACs with various coordination environment.Here,we have applied large-scale density functional theory(DFT)computations to assess stability against forming isolated single-atom,aggregation and dissociation,of BACs on nitrogen-doped graphene.And,the ORR activity on the 3d-3d heteronuclear BACs was calculated.The main research contents of this paper are as follows:(1)The thermodynamic stability of 136 late transition metal BACs with two coordination structures was systematically calculated.Among,most BACs show good thermodynamic stability.We found that the stability of BACs for configurations 4 is related to the number of valence electrons,electronegativity and the atomic radius of the metal element.And we constructed descriptors with the number of valence electrons,electronegativity and the atomic radius of the metal element as key internal factors to evaluate the structural stability of BACs,which are verified by experimental results.This method provides a universal screening standard for the design of BACs with high stability.(2)The thermodynamic ORR activities of 15 heteronuclear BACs with two coordination structures were calculated.12 bi-atom sites of them are higher thermodynamic activity than Pt(111).The free energy of OH*(ΔGOH*)can be used as an energy descriptor to evaluate the ORR reaction activity of the catalyst.When ΔGOH*is between 0.8 and 1.11 eV,BACs have high theoretical activity for ORR in acidic conditions.Moreover,the kinetic analysis of the diatomic structure with high thermodynamic activity was carried out.The results show that,the half-wave potentials of most BACs are higher than Pt,which is consistent with the results obtained by thermodynamics.