Energy Harvesting from Carbon Dioxide Capture through an Ionic Liquid Based Supercapacitor

Nowadays, Earth is undergoing effects of climate change due to the exponential increase of greenhouse gasses's emissions. The main component of greenhouse emissions is carbon dioxide (CO2), which is estimated responsible for about 60% of global warming generated by human activities, and its concentration is increased by 40% with respect to the concentration at the beginnings of industrial era. This increase is due to several factors such as the combustion of coal, oil and gas and the progressive deforestation: this last phenomenon generates a sort of bottleneck in the so called biogeochemical "carbon cycle". Deforestation causes the lack of one of the natural regulating sources of carbon dioxide concentration. Scientific community set an increase of 2°C (with respect to the pre-industrial global temperature) as the threshold beyond which there is a much higher risk that dangerous and possibly catastrophic changes in the global environment will occur. At the moment the increase of the temperature has reached about +0,85°C thanks to greenhouse gasses. All technologies developed in CO2 capturing have to be intended in the reduction of global warming. The goal of the presented work is to develop a device able to cut down greenhouse emissions by reusing human produced carbon dioxide. This can be done exploiting the free energy released each time two solutions with different compositions are mixed. Even if this phenomenon holds true both for liquids and gases, in last decades it was deeply investigated for what concerns liquid sources (CapMix), while few technologies are available to harvest free energy coming from gas sources. The adopted structure is an electrical double layer super-capacitor based on ionic liquid electrolyte. Special attention should be paid to the choice of the electrolyte which should work both as an electrolyte and CO2 absorbing medium in a CapMix cell. Among the tested ionic liquids, the choice fell on an Imidazole based ionic liquid, which showed excellent absorption rates of gas, being able to capture 15.67% of CO2 over the total mass. This work is a proof of concept of a novel not yet studied mechanism, which is able to work without any imposed external bias. When a CO2 gas stream is flushed through the supercapacitor, the gas strongly affects the electrode/IL interface and the IL physico-chemical properties, producing a change in the potential difference between the electrodes. In this way it is possible to convert the mixing energy into electrical energy.