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

Electric-driven reduction of CO2 to high value-added chemicals is considered to be one of the most promising methods for CO2 utilization. In this work, a novel aprotic electrolyte consisting of phenoxy-nitrile bifunctional ionic liquid ([TBP][p-CN-PhO]) and acetonitrile was designed for CO2 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 CO2 electroreduction to oxalate. The significant performance of CO2 electroreduction was attributed to the strong interaction energies of phenoxy and nitrile groups with CO2 molecules in the bifunctional ionic liquid, which greatly facilitates CO2 activation to form CO2– radicals by a new bulk-phase pathway and then dimerizes into C2O42– at a lower energy barrier.