Electrochemical Impedance Studies of CO2 Reduction in Ionic Liquid/Organic Solvent Electrolyte on Au Electrode.

Electrochemical reduction of CO 2 has been studied in 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([Bmim][CF 3 SO 3 ])/propylene carbonate (PC) solution on Au electrode. The linear sweep voltammetry measurements show that [Bmim][CF 3 SO 3 ] has significant catalytic effect toward CO 2 reduction. In order to study the mechanism of CO 2 reduction in [Bmim][CF 3 SO 3 ]/PC on Au electrode, the electrochemical impedance spectroscopy is employed. The experiment results show that the electrochemical impedance spectroscopy detected in [Bmim][CF 3 SO 3 ]/PC is different from that detected in tetrabutylammonium trifluoromethanesulfonate ([Bu 4 N][CF 3 SO 3 ])/PC solution. The reasonable explanation is that [Bmim] + is absorbed on the Au electrode, leading to the formation of ionic liquid film. During the CO 2 reduction process, absorbed CO 2 is reduced to CO 2 − radical via single electron transfer. The generated CO 2 − radical interacts with [Bmim] + and inducing the formation of [Bmim-CO 2 ] (ad) . Thus, the activation energy and overpotential of CO 2 reduction are reduced. The electrochemical impedance spectroscopy can be used as a methods to investigate the mechanism of CO 2 reduction in non-aqueous solution. [ABSTRACT FROM AUTHOR]