CARBON DIOXIDE CAPTURE AND ELECTROCHEMICAL CONVERSION WITH IONIC LIQUIDS

The exponential increase in the concentration of greenhouse gasses in the atmosphere is considered one of the most important reason for climate change. Carbon Dioxide is the most significant anthropogenic gas that contributes in global warming. CO2 capture and storage (CCS) has been proposed as one of the most important invention to mitigate CO2 emissions. Moreover, conversion of carbon dioxide into energy-rich chemicals is a viable approach to reducing the global carbon footprint. The most common techniques to remove CO2 from gas streams are the chemical and physical adsorption by liquid solvents. Traditionally, aqueous amine solutions have been used as chemical solvents because of their high selectivity, high reactivity and low price. Unfortunately, they present also many disadvantages associated with the high energy demand required for the solvent regeneration, corrosion issues and loss of solvent because of their high volatility. Hence, in the need to find more efficient solvents for CO2 capture and conversion, Ionic Liquids (ILs) have been highlighted as very good alternatives to common amine solution. (1) Within this field lies this research, which in turn is part of a much broader European project called SunCoChem. For this project we are testing the stability and performance of various ionic liquids, provided by Iolitec Ionic Liquids technologies GMBH, and in particular their ability to capture and electrochemically convert a pure CO2 stream to CO with high efficiencies. The ionic liquids were tested in a two-compartment H-type electrochemical cell. In the anodic chamber a nickel mesh electrode was immersed in a solution of potassium hydroxide and in the cathodic one a silver foil cathode was employed in a solution of CH3CN and ionic liquid. An organic solvent was used to favor the dissolution of the ionic liquid and the homogenization of the solution. The Ionic Liquids (ILs) tested so far have a cationic part based on imidazole, which is expected to stabilize and lower the activation energy for the reduction of CO2, namely [BMIM][BF4], [BMIM][CH3CO2], [BMIM][CF3CO2] and [BMIM][CF3SO3]. This trend was confirmed by a shift to more positive potentials of the onset (~ 0.5V) for the CO2 reduction reaction in the presence of these Ionic Liquid. During the CP studies, some ILs evidenced a decrease in the applied potential indicating the increase of the electrolyte conductivity on difference to the behavior of the most used [BMIM][BF4] IL in the same organic solvent. Our results evidence relevant current density values, a good stability during chronopotentiometry (CP) tests and a high selectivity towards the target product: CO, which however change depending on the used IL. AKCNOWLEDGMENT The research leading to these results has received funding from the European Union’s Horizon 2020 Research and Innovation Action programme under the SunCoChem project (Grant Agreement No 862192). REFERENCES: (1) Shokat Sarmad et al, Carbon Dioxide Capture with Ionic Liquids and Deep Eutectic Solvents: A New Generation of Sorbents, 2016, https://doi.org/10.1002/cssc.201600987