Electrochemical carbon dioxide reduction in ionic liquids at high pressure

Abstract

Imidazolium ionic liquids are potentially useful solvents for both carbon dioxide reduction conversion and capture. In particular electrocatalytic CO₂ reduction has been shown to occur at low overpotentials using a 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([EMIM][OTf]) and water mixed solvent. A limitation of such solvent systems is their viscosity, making it hard to maintain reasonable catalytic current densities without energy intensive stirring/agitation of the electrolyte. Here we explore the electrochemical reduction of CO₂ at high pressures (0.1 to 5.1 MPa) and demonstrate a correlation between the volume of expansion of the ionic liquid and the achieved catalytic current density. The improved electrocatalytic behaviour is proposed to be due to both the increased bulk CO₂ concentration and the improved mass transport properties of the gas-expanded ionic liquid. These initial studies at pressure represent a step towards realising an integrated CO₂ capture and utilisation system based around a common ionic liquid.