A coupled system for electrochemical capture and conversion of CO2 into syngas

As the 21st century progresses, the problem of global warming becomes more and more pressing on our planet. In this regard, the proposed thesis sets itself the initial objective of highlighting this phenomenon to the reader, probing the numbers, the relations between temperature and climate-changing gas emissions (GHG) and the effects of humanity, which prompted the concentration of CO2 in the air over 400 ppm. Subsequently, the concept of problem mitigation is proposed to the reader, analyzing different aspects such as the carbon lock-in, the policies currently in place to limit the temperature increase beyond 2°C, and the possible solutions. In particular, one of the possible solutions is investigated, namely the capture of CO2 - the most present greenhouse gas in the environment. It consists in removing this gas either from the exhaust gases resulting from combustion or from the atmosphere. the experimental part of the thesis is divided in three parts. Firstly, the thermodynamics governing the process is analyzed, which requires a minimum energy in the order of 5-6 kJ per mole of CO2 captured by exhaust gases and 20-21 kJ if captured from the atmosphere. The second part is constituted by the study and experimentation of an electrochemical capture system, based on the electrodialysis of NaHCO3, which releases CO2 and produces NaOH, being able to capture the CO2 present in a gaseous mixture regenerating the solution itself and allowing continuous operation over time. A simulated exhaust gas with CO2 concentration equal to 16% was employed as input, obtaining CO2 with purity up 98% as output. The continuous operation of the system was verified for up to 8 consecutive hours. The operation parameters have been optimized it, with a flow of 6 ml/min of CO2 captured compared to 20 ml/min in the inflow. Furthermore, from the capture system, it is also possible to obtain valuable by products such as H2 and O2 In the last part of the work, the system was coupled with a CO2 electroreduction device to produce syngas. The latter consists of a mixture of CO - deriving from the reduction of CO2 - and H2 - deriving from the water splitting of the water present in the system- capable of being reused as fuel or as a platform for other molecules. In this way, it has been possible to develop a new system, consisting in a loop capable of capturing CO2 from combustion processes (avoiding contributing to global warming), and of directly transforming it into another reusable substance through a directly coupled system.