Reduction of Carbon Dioxide to Formate at Low Overpotential Using a Superbase Ionic Liquid

Abstract

A new low‐energy pathway is reported for the electrochemical reduction of CO 2 to formate and syngas at low overpotentials, utilizing a reactive ionic liquid as the solvent. The superbasic tetraalkyl phosphonium ionic liquid [P 66614 ][124Triz] is able to chemisorb CO 2 through equimolar binding of CO 2 with the 1,2,4‐triazole anion. This chemisorbed CO 2 can be reduced at silver electrodes at overpotentials as low as 0.17 V, forming formate. In contrast, physically absorbed CO 2 within the same ionic liquid or in ionic liquids where chemisorption is impossible (such as [P 66614 ][NTf 2 ]) undergoes reduction at significantly increased overpotentials, producing only CO as the product.