Direct electroreduction of CO 2 from simulated flue gas using ionic liquid electrolyte

Direct electroreduction of CO 2 from flue gas to high‐valued chemicals mitigates CO 2 emissions but suffers low product selectivity. Herein, an ionic liquid electrolyte consisting of 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([C 4 mim][BF 4 ]), acetonitrile and H 2 O (5 wt%) was optimized for direct CO 2 electroreduction to CO (eCO 2 ‐to‐CO) from simulated flue gas. At −2.3 V (vs. Ag/Ag + ), the system delivers 95.6% CO Faradaic efficiency and 14.9 mA·cm −2 partial current density in H‐cell, representing one of the state‐of‐the‐art systems of low‐concentrated eCO 2 ‐to‐CO. Moreover, the existence of H 2 O improves electrolysis stability of the system from 5 to 150 h. In situ spectroscopy and computations revealed that H 2 O‐dissociated active H regenerates imidazolium C 2 ‐H sites of [C 4 mim][BF 4 ], lowering the energy barrier for *COOH formation. Techno‐economic assessment demonstrated a considerable reduction in CO production cost via direct eCO 2 ‐to‐CO from flue gas. This work is different from catalyst design and provides a novel solution for eCO 2 ‐to‐CO from flue gas using IL electrolyte strategy.