Surface Ligand Promotion of Carbon Dioxide Reduction through Stabilizing Chemisorbed Reactive Intermediates

We have explored functionalizing metal catalysts with surface ligands as an approach to facilitate electrochemical carbon dioxide reduction reaction (CO₂RR). To provide a molecular level understanding of the mechanism by which this enhancement occurs, we combine in situ spectroscopy analysis with an interpretation based on quantum mechanics (QM) calculations. We find that a surface ligand can play a critical role in stabilizing the chemisorbed CO₂, which facilitates CO₂ activation and leads to a 0.3 V decrease in the overpotential for carbon monoxide (CO) formation. Moreover, the presence of the surface ligand leads to nearly exclusive CO production. At -0.6 V (versus reversible hydrogen electrode, RHE), CO is the only significant product with a faradic efficiency of 93% and a current density of 1.9 mA cm^-2. This improvement corresponds to 53-fold enhancement in turnover frequency compared with the Ag nanoparticles (NPs) without surface ligands.