Ionic liquid [C3mim]OTf aqueous solution: Green high efficiency electroreduction for carbon dioxide at room-temperature

Abstract

The ionic liquids (ILs) solvent have been drawn much attention in green chemistry field. However, ILs are usually dissolved in organic solvents, which can cause some evaporation pollution. Here, the conversion technologies of carbon dioxide (CO2) was explored with Pb, In and Sn electrodes in the 1-propyl-3-methylimidazolium trifluoromethane sulfonate ([C3mim]OTf) aqueous solution. The application of ILs not only solved the problem of organic solvents, but increased the efficiency of CO2 chemistry conversion. The influences of applied potential, electrolyte concentration and working electrodes on electroreduction of CO2 was investigated. The experiments show that the dominant reaction on Pb, In and Sn electrodes in [C3mim]OTf is CO2 electroreduction rather than hydrogen evolution reaction. The Faradaic efficiency of HCOOH was increased first and then decreased along with the applied potential (vs. Ag/Ag+) in test process. Compared to Pb and In electrodes, Sn electrodes have the highest activity for the electroreduction of CO2. Notably, when the partial current density reached 9.3 mA·cm−2 at −2.2 V (vs. Ag/AgCl), the Faradaic efficiency was reached up to 35.45% on the Sn electrodes in 40 mg·mL−1 [C3mim]OTf aqueous solution.