Insights into Carbon Dioxide Electroreduction in Ionic Liquids: Carbon Dioxide Activation and Selectivity Tailored by Ionic Microhabitat

Abstract Electroreduction of carbon dioxide (CO 2 ) into high value‐added products is a potential solution to a reduction in CO 2 levels and its utilization. One major challenge is the lack of an efficient system that can highly selectively reduce CO 2 into desirable products with low energy consumption. Ionic liquids (ILs) have been used as electrolytes for the electroreduction of CO 2 , and it has been proven that the CO 2 –cation complex results in a low‐energy pathway. In this work, an ionic microhabitat (IMH) has been built for CO 2 electroreduction, and a novel anion‐functionalized IL, 1‐butyl‐3‐methylimidazolium 1,2,4triazolide ([Bmim][124Triz]), has been designed as the reaction medium. The results showed that the IMH played a key role in enhancing the performance of CO 2 electroreduction, especially in dominating the product selectivity, which is recognized to be a great challenge in an electroreduction process. New insights into the role of the IMH in higher CO 2 solubility, bending linear CO 2 by forming the [124Triz]–CO 2 − adduct, and transferring activated CO 2 into the cathode surface easily were revealed. The Faradaic efficiency for formic acid is as high as 95.2 %, with a current density reaching 24.5 mA cm −2 . This work provides a promising way for the design of robust and highly efficient ILs for CO 2 electroreduction.