Amine modification enables selective CO2 electroreduction to ethanol via coupling of carbon-containing intermediates

Abstract

Electrochemical CO₂-to-ethanol conversion faces challenges due to competing ethylene formation. We demonstrate a strategy steering selectivity toward ethanol by modifying copper nanowires with N,N,N′,N′-tetramethylethylenediamine (TMe). The TMe-Cu catalyst achieved a remarkable ethanol faradaic efficiency of ∼58.8 at −0.97 V vs. RHE in H cells. Implementation in an alkaline flow electrolyzer yielded an ethanol partial current density of −216.2 mA cm⁻². Combined experimental and computational analyses revealed that TMe modification creates an aerophilic-hydrophobic interface boosting CO₂ adsorption and increasing ∗CO intermediate coverage on Cu active sites. In situ spectroscopic studies and controlled experiments identify an ethanol formation pathway involving asymmetric ∗CO–∗CH_x coupling followed by ∗OCH₂CH₃ reduction, while completely suppressing ethylene generation. This work provides mechanistic insights into steering C–C coupling pathways through microenvironment engineering, offering a promising approach for sustainable multi-carbon alcohol synthesis from CO₂.