A First-Principles Screening for Axial Ligand Regulation of Electrocatalytic Carbon Dioxide Reduction on Dual-Metal Atomic Catalysts (M1M2N6-R)

Abstract

A primary challenge in the carbon dioxide reduction reaction (CO₂RR) is the rational design and engineering of high-efficiency electrocatalysts. A series of M₁M₂N₆ catalysts (M₁M₂ = 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 CO₂RR performance in this work. The adsorption energies of three distinct ligands at the M₁–M₂ bridge site are evaluated to quantitatively assess the ligand stabilization. On pristine and ligand-engineered M₁M₂N₆ catalysts, the free energy variation along CO₂RR 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 C₂H₅OH and C₂H₆. However, –COH and –OH modification excludes *CO-intermediate formation and directs the reaction toward CH₄ and CH₃OH 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.