(581b) Formation of Carbon-Nitrogen Bonds in Carbon Monoxide Electroreduction (invited)

Electrochemical conversion of carbon dioxide (CO₂) using renewable electricity is an attractive means for sustainable production of fuels and chemicals. Copper (Cu) has a unique capability of catalyzing carbon-carbon (C-C) bond formation to form high-value multi-carbon (C₂₊) products. While highly alkaline electrolytes are often used to enhance C₂₊ selectivity, the inevitable reaction of hydroxide ions with CO₂ to form undesired carbonates at the electrode-electrolyte interface disrupts the electrolysis process. This fundamental challenge can be solved by decoupling the CO₂ electrolysis into a two-step process, where CO₂ is first electrochemically reduced to carbon monoxide (CO) at neutral conditions, followed by CO electroreduction to produce C₂₊ chemicals in alkaline environments. Nonetheless, only four major C₂₊ products, i.e., ethylene, acetate, ethanol, and n-propanol, have been reported for CO₂/CO electrolysis in aqueous electrolytes.

In this talk, we will present a new study to expand beyond this limited range of simple C-C coupling by demonstrating electrochemical production of acetamide with nearly 40% Faradaic efficiency at a current density of 300 mA/cm², where the carbon-nitrogen (C-N) bond is formed through CO electroreduction in the presence of ammonia. Full solvent quantum mechanical calculations showed earlier that the under neutral or basic conditions the reaction mechanism involves CO dimerization and sequential transfer of H from two surface water to form the (HO)C*-C*OH intermediate that subsequently leads through two separate pathways to form C₂H₄ (90%) and ethanol (10%). We show now that (HO)C*-C*OH is also hydrolyzed to *C=C=O, which in turn reacts with NH₃ to form intermediates leading to acetamide while suppressing formation of other C₂ products. We also successfully extended the range of C-N containing products to N-methylacetamide, N-ethylacetamide, N,N-dimethylacetamide, acetic monoethanolamide, and aceturic acid. Our results provide useful mechanistic insights into Cu-catalyzed CO₂/CO electroreduction and demonstrate the construction of carbon-heteroatom bonds in CO₂/CO electrolysis. This largely expands the scope of electrocatalytic CO₂ utilization pathways for sustainable chemical production.