Urea-Based Multipoint Hydrogen-Bond Donor Additive Promotes Electrochemical CO₂ Reduction Catalyzed by Nickel Cyclam

We report that a urea-based multipoint hydrogen-bond donor additive leads to an enhancement in activity for electrochemical CO2 reduction to CO catalyzed by Ni cyclam without altering this catalyst's high selectivity for CO2 versus proton reduction. Comparison of peak catalytic currents in the presence of a bis(aryl)urea additive versus an isostructural amide as a one-point hydrogen-bond counterpart, as well as other weakly coordinating acids with comparable pKa values, reveals that the urea preferentially augments CO2 electrocatalysis. This observation suggests that the ability of the urea to form cooperative hydrogen-bond interactions is critical for the observed increases in activity rather than its acidity alone. Indeed, the boost in catalytic activity is observed in acetonitrile electrolyte containing up to 1 M water, indicating the organourea's role as a cocatalyst rather than a stoichiometric additive. This work establishes a starting point for applying principles of organocatalysis to electrocatalysis, where rational design and implementation of organic additives to electrocatalytic platforms can be a promising avenue to enhance activity and/or control product selectivity without requiring elaborate ligand synthesis.