Kinetic Origins of Limited C-C coupling on Dual-Atom Catalysts in Electrochemical CO2 reduction

Dual-atom catalysts (DACs) composed of two adjacent metal atoms have been widely investigated for the electrochemical CO2 reduction reaction (CO2RR) due to their high atomic efficiency, structural tunability, and promising electrocatalytic activity. Owing to their unique dual-stie geometry, DACs have been theoretically proposed to facilitate C-C coupling and promote multi-carbon (C2+) product formation. However, despite many theoretical calculations, most DACs predominantly produce CO in experiments, and the atomistic origin of this limited C-C coupling activity remains elusive. In this work, we employed constant-potential ab initio molecular dynamics simulations (AIMD) with an explicit solvation model to investigate C-C coupling pathways on a Cu2-N-C DAC. While these coupling pathways were found to be thermodynamically feasible, CO* dimerization was kinetically hindered due to the weak interaction between Cu and the carbon atoms in the intermediate. Furthermore, weak hydrogen bonding between CO* and surrounding water molecules suppressed protonation steps, thereby disfavoring alternative coupling pathways such as CO*-CHO* and CO*-COH*. As a result, CO* desorption became the most kinetically favorable reaction. These findings provide mechanistic insights into the poor C-C coupling activity observed on DACs and highlight the importance of capturing dynamic solvation effects when modeling electrochemical reactions.