In Situ Spectroscopic Characterization of an Intermediate of CO<sub>2</sub> Electroreduction on a Au Electrode in Room-Temperature Ionic Liquids
Kenta Motobayashi, Yoshiki Maeno, Katsuyoshi Ikeda
Abstract
Room-temperature ionic liquids (RTILs) are fascinating electrolytes for CO2 electroreduction owing to their low overpotentials. Although it is well accepted that the key to understanding the low overpotential is the stabilization of the intermediate, its mechanism is still under discussion. To elucidate the intermediate stabilization mechanism, RTIL/electrode interfaces under CO2 reduction were observed using surface-enhanced infrared absorption spectroscopy (SEIRAS). This in situ interface-selective spectroscopy allows us to detect CO2•– that is not observed in aqueous solutions. For a negative-going potential scan, identical onsets were observed for increasing SEIRA band intensities of CO2•– and RTIL cations and reduction current. This result indicates that RTIL cations stabilize CO2•– on the electrode, and this stabilizing effect can be ascribed to the origin of the low overpotentials of CO2 electroreduction in RTILs.