Electrochemical CO2 reduction to CO facilitated by MDEA-based deep eutectic solvent in aqueous solution

Electrocatalytic CO 2 reduction (ECO 2 R) is an environment-friendly way to convert CO 2 into profitable products. Amine solution recently has been employed as an electrolyte in ECO 2 R but suffers from low efficiency. Herein, aqueous solutions containing different amine-based deep eutectic solvents (DESs) were used as electrolytes for CO 2 reduction. The effect of different DESs on the CO 2 reduction was investigated at Ag, Cu, and Zn metal electrodes. Tafel and electrochemical impedance spectroscopy (EIS) were applied to understand the CO 2 reduction. DES in aqueous solution facilitates the CO 2 reduction to CO with higher faradaic efficiency of CO (FE CO ) than amine solutions and a mixture of hydrogen bond acceptor (HBA) and hydrogen bond donor (HBD). Both HBD and HBA have an influence on CO 2 reduction. [Monoethanolamine hydrochloride] [methyldiethanolamine] ([MEAHCl][MDEA]) gives high FE CO , 71% FE CO at −1.1 V vs RHE at Ag electrode, 33% higher than [MEAHCl][MEA]. Experimental results and EIS analysis reveal that the facilitation of CO 2 reduction to CO probably stems from a synergistic effect of nano-size agglomerate dispersion on Ag-surface, bicarbonate formation, exchange current density , and Cl − ions present in DESs. These findings present a feasible method to employ the aqueous MDEA-based DES solution as an electrolyte for CO 2 reduction.