Detrimental Effects of Monoethanolamine and Other Amine-Based Capture Agents on the Electrochemical Reduction of CO₂

Reactive carbon capture (RCC) is a promising solution for carbon capture and utilization. RCC involves CO 2 capture, typically with amine solutions to form carbamate, followed by immediate conversion into value-added chemicals and fuels, typically via electrochemical means. RCC may enhance CO 2 reduction (CO 2 R) by overcoming the inherent limiting low solubility of CO 2 in aqueous solutions. In this work, we present a systematic study of the influence of monoethanolamine (MEA) on CO 2 R performance over an Ag cathode in KHCO 3 electrolytes. Contrary to prior work, the study finds no evidence for the direct reduction of carbamate anions. Instead, the presence of MEA suppresses the rate of CO formation while increasing that of H 2 . These results are supported by a boundary-layer continuum model of mass transport and reaction that correctly predicts experimental trends and demonstrates that MEA reduces the concentration of CO 2 near the cathode. Thus, alternative strategies are necessary to achieve RCC in aqueous environments.