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 pK_a 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.