Efficient Electrochemical Reduction of CO2 to CO in Ionic Liquids

Electrochemical reduction of carbon dioxide (CO2) to CO is a promising strategy. However, achieving high Faradaic efficiency with high current density using ionic liquid (IL) electrolyte remains a challenge. In this study, the new IL N-octyltrimethyl ammonium 1,2,4-triazole ([N-1118][TRIZ]) shows outstanding performance for electrochemical reduction of CO2 to CO on the commercial Ag electrode, and the current density can be up to 50.8 mAcm(-2) with a Faradaic efficiency of 90.6 %. The current density of CO is much higher than those reported in the IL electrolyte. In addition, the density functional theory (DFT) calculation further proved that [N-1118][TRIZ] interact with CO2 to form [N-1118](+)[TRIZ-CO2](-) complex which played a key role in reducing the activation energy of CO2. The formation of [N-1118](+)[TRIZ-CO2](-) complex was verified by Fourier Transform Infrared (FTIR) spectroscopy. According to the molecular orbital theory, the electrons obtained from IL was filled in the anti-bonding orbit (pi*) of the CO2, resulting in reducing the C=O bond energy. This work provides a new strategy to design novel ILs for high efficiency electrochemical reduction of CO2 to CO.