Phenoxy-Nitrile Bifunctional Ionic Liquid for Efficient Electroreduction of CO2 to Oxalate

Electric-driven reduction of CO 2 to high value-added chemicals is considered to be one of the most promising methods for CO 2 utilization. In this work, a novel aprotic electrolyte consisting of phenoxy-nitrile bifunctional ionic liquid ([TBP][p-CN-PhO]) and acetonitrile was designed for CO 2 electroreduction to oxalate, which shows the maximum Faradaic efficiency (FE) of 84.9% at −2.6 V. Importantly, a high oxalate formation rate of 233.7 μmol·cm –2 ·h –1 and oxalate FE of 73.9% were simultaneously achieved to break the trade-off effect at −2.8 V in the bifunctional ionic liquid electrolyte, which is also one of the state-of-the-art performances for CO 2 electroreduction to oxalate. The significant performance of CO 2 electroreduction was attributed to the strong interaction energies of phenoxy and nitrile groups with CO 2 molecules in the bifunctional ionic liquid, which greatly facilitates CO 2 activation to form CO 2 – radicals by a new bulk-phase pathway and then dimerizes into C 2 O 4 2– at a lower energy barrier.