Highly efficient electrochemical upgrade of CO2 to CO using AMP capture solution as electrolyte

Abstract

Electrochemical CO2 reduction reaction (ECO2RR) offers an eco-friendly way to produce value-added products by utilizing the waste CO2 from the environment. Recently, amines have been utilized as electrolytes for direct conversion of CO2 but processes were energy-intensive and lack selectivity due to the formation of highly stable carbamate. 2-amino-2-methyl-1-propanol (AMP) is a sterically hindered amine, produces less stable carbamate, and generates more HCO3−. Herein, ECO2RR performance using AMP aqueous solution as electrolyte was investigated over Ag, Cu, and Zn metal electrodes. Ultimately, 91 ± 7% CO selectivity on HCl modified polycrystalline Ag electrode at −0.91 V vs RHE in 1 M AMP aqueous solution in the presence of CTAB was achieved, 1.7 times greater than in 1 M aqueous ethanolamine (MEA) solution. Synergetic effects of unstable AMP-carbamate, generation of nano-agglomerates on pitted/porous Ag surface arising from HCl treatment, and a compact electrical double layer due to CTAB present are responsible for the high selectivity of CO. Our findings provide the understanding of electrode-electrolyte interactions and offer a facile strategy to directly convert CO2 to CO from CO2 capture solutions.