A Bifunctional Ionic Liquid for Capture and Electrochemical Conversion of CO2 to CO over Silver

Electrochemical conversion of CO2 requiresselectivecatalysts and high solubility of CO2 in the electrolyteto reduce the energy requirement and increase the current efficiency.In this study, the CO2 reduction reaction (CO2RR) over Ag electrodes in acetonitrile-based electrolytes containing0.1 M [EMIM]-[2-CNpyr] (1-ethyl-3-methylimidazolium 2-cyanopyrolide),a reactive ionic liquid (IL), is shown to selectively (>94%) convertCO(2) to CO with a stable current density (6 mA center dot cm(-2)) for at least 12 h. The linear sweep voltammetryexperiments show the onset potential of CO2 reduction inacetonitrile shifts positively by 240 mV when [EMIM]-[2-CNpyr] is added.This is attributed to the pre-activation of CO2 throughthe carboxylate formation via the carbene intermediate of the [EMIM](+) cation and the carbamate formation via binding to the nucleophilic[2-CNpyr](-) anion. The analysis of the electrode-electrolyteinterface by surface-enhanced Raman spectroscopy (SERS) confirms thecatalytic role of the functionalized IL where the accumulation ofthe IL-CO2 adduct between -1.7 and -2.3 Vvs Ag/Ag+ and the simultaneous CO formation are captured.This study reveals the electrode surface species and the role of thefunctionalized ions in lowering the energy requirement of CO2RR for the design of multifunctional electrolytes for the integratedcapture and conversion.