(Best Poster Award - 2nd Place) Energy Harvesting from CO2 Emission Exploiting an Ionic-Liquid Based Electrochemical Capacitor

Abstract

Global warming is one of the most serious problems that the humanity is facing in his history.Since 1900 to nowadays, the global temperature has risen by 1 °C and, according to the scientificcommunity, the cause is related to the climate-changing emissions due to anthropogenic activities.In order to avoid an environmental disaster, 196 countries have signed the Paris agreement thataims to maintain global warming below 1.5 °C compared with pre-industrial levels.The reduction of greenhouse gas emissions is a key issue in contemporary science, and in thiscontext, the ability of certain ionic liquids (ILs) to capture carbon dioxide has attracted a lot ofinterest. The idea presented in this work is to design an electric double layer supercapacitor whichis able to harvest energy by exploiting the reaction between an ionic liquid and carbon dioxide. Inparticular, the system consists of two carbon-based electrodes and a polymeric separator soakedin ionic liquid. The use of carbon electrodes ensures a high surface area and excellent electricalconductivity while imidazole-based ionic liquid acts and as electrolyte and as capture media.The operating principle of this system is a novel mechanism which exploits the formation of avoltage drop across the device when the electrode-IL interfaces are different; the two differentinterfaces are ensured by the presence of imidazole carbamate in a part of the cell (Im − CO2reaction’s product) and just imidazole in the other part.Unfortunately the high viscosity of ionic liquids affects a lot the carrier transport and consequentlythe device’s performance too; this aspect worsens when imidazole reacts with CO2. Improved ionmobility is achieved by reducing the ion pairing through the use of high dielectric solvents capableto screen the ions’ electric field. Polar aprotic solvents tend to have large dipoles making themsuitable for the solvation of charged species.Several mixtures have been analyzed to detect the best dilution which guarantees high ionic mobilitystill maintaining a large amount of active species.A further performance improvement has been achieved through the engineering of the electrodes,namely the capacitance of the supercapacitor has been enhanced by exploiting the huge specificsurface area of the activated carbon.The results show that all the upgrades mentioned lead to an improvement of 500 times in terms ofharvested energy.Acknowledgement: This result is part of a project that has received funding from the European Research Council(ERC) under the European Union’s ERC Starting Grant Grant agreement No. 949916 Figure 1