Electrochemical C-N Bond Formation from CO₂ and Nitrate Using Molecular Catalysis

The emerging direction of electrochemical C-N bond formation from CO₂ and small N-containing molecules has gained wide attention in recent years as a sustainable route in producing high-value products such as amines and amides. To date, the majority of C-N bond electrocatalysts discovered have been heterogeneous and/or solid-state in nature, which have some limitations when investigating structure-activity relationships toward the buildup of a fundamental knowledge base. Molecular electrocatalysts, on the other hand, have a wide range of advantages for fundamental studies, as these catalysts can be easily tuned, showing direct relationships between catalytic activity and the metal center, ligand, secondary coordination sphere, and much more. To this end, we demonstrate the use of a monohydroxy terpyridine nickel complex (NitpyOH) as a homogeneous molecular electrocatalyst for C-N bond formation in an aqueous system. We demonstrate the production of formamide as a major C-N product with a peak Faradaic efficiency of 35% and a partial current density of 0.095 mA cm^-2 at -0.69 V vs RHE using 1 mM NitpyOH. Finally, structure-activity correlations and a combination of in situ spectroscopy, electroanalytical techniques, and computational modeling elucidated the key aspects of the catalytic mechanism responsible for formamide production via C-N coupling. The insight developed here paves the way for the use of molecular systems in electrochemical small-molecule cross-coupling reactions.