Efficient Electrochemical Reduction of CO 2 to CO in Ionic Liquids

Abstract Electrochemical reduction of carbon dioxide (CO 2 ) 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 CO 2 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 CO 2 to form [N 1118 ] + [TRIZ‐CO 2 ] − complex which played a key role in reducing the activation energy of CO 2 . The formation of [N 1118 ] + [TRIZ‐CO 2 ] − 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 ( π *) of the CO 2 , resulting in reducing the C=O bond energy. This work provides a new strategy to design novel ILs for high efficiency electrochemical reduction of CO 2 to CO.