Mechanism investigation of direct electrochemical reduction of CO2-loaded 2-(ethylamino)ethanol solution into CO

Abstract

Carbon capture and utilization (CCU) has attracted considerable interest recently as CO2 emission and global warming have greatly affected various aspects of the environment, economy, and society. However, energy consumption during CCU must be substantially reduced. In this study, we propose an alternative approach using electrochemical reduction to directly convert CO2-loaded amine solutions into CO. The effects of the electrodes, temperature, potential, and CO2 loading on the Faradaic efficiency (FE) of CO were comprehensively investigated. The Ag NPs/CP electrode showed good catalytic performance on the electrochemical reduction of CO2-loaded amine solution to CO. By comparing the chemical composition in the solution before and after the electrochemical reaction, we determined that the main source of CO might be free CO2, which is mainly converted from bicarbonate rather than carbamate. In addition, electrochemical impedance spectroscopy was used to investigate the resistance during the reaction. The electric double-layer was found over the electrode surface when different amine solutions were used as the electrolyte. The spatial structure of ammonium cations and carbamate plays a key role in the FE of CO in this process.