Abstract
A primary challenge in the carbon dioxide reduction reaction (CO(2)RR) is the rational design and engineering of high-efficiency electrocatalysts. A series of M(1)M(2)N(6) catalysts (M(1)M(2) = NiNi, CoNi, CoFe, CoCo) with precisely tailored axial ligands (R = -OH, -COH, -CN) have been high-throughput screened out to exhibit optimal electrocatalytic activity, which is extended to further estimate their CO(2)RR performance in this work. The adsorption energies of three distinct ligands at the M(1)-M(2) bridge site are evaluated to quantitatively assess the ligand stabilization. On pristine and ligand-engineered M(1)M(2)N(6) catalysts, the free energy variation along CO(2)RR pathways leading to C1 products reveals that the initial proton-coupled electron transfer to form the *HCOO/*COOH intermediate is the main potential-limiting step of yielding the key intermediate CO*. The formation barrier energy difference of <0.06 eV between *HCOO and *COOH intermediates on pristine CoCo/CoFe/CoNi and CN-functionalized CoFe/CoCo catalysts facilitates *CO intermediate generation and enables the subsequent *CO-*CO coupling to C2 products for formation of C(2)H(5)OH and C(2)H(6). However, -COH and -OH modification excludes *CO-intermediate formation and directs the reaction toward CH(4) and CH(3)OH production due to the large kinetic energy difference of 0.96-1.11 eV between *HCOO and *COOH. Our results provide a possible axial ligand engineering strategy of regulating C1/C2 product selectivity on different dual-atom catalysts.