Integrated CO₂ Capture and Electrochemical Conversion

Abstract

The large concentrations of anthropogenic CO2 emissions present in our atmosphere are causing a severe thread on the world as we know it. It is therefore highly necessary to move away from fossil fuels to sustainable alternatives. In order to do so, lots of research has focused already on finding new ways to create renewable energy, through for example solar and wind energy. These renewable energy sources will be able to replace the energy that we need to warm our houses and drive our cars. However, these technologies are not able to replace the chemicals that we use in our daily lives that are made through fossil-based processes. For example, plastic bottles and packing, synthetic fabrics such as polyester and nylon, cosmetics, and detergent are all made from fossil-based chemicals. An sustainable alternative process to make these chemicals is through electrochemical CO2 reduction, where CO2 is converted into chemicals by applying electricity. This involves capturing CO2 from the atmosphere and transforming it into a value-added chemical. In this way, CO2 becomes a resource instead of a waste gas that is vented off into the atmosphere and a so called circular carbon economy can be established.

Typical CO2 capture systems use a thermal step to remove the captured CO2 from the capture solvent and regenerate the solution such that it can be recycled back to the capture step. This thermal process is highly energy intensive and therefore a costly step in the CO2 capture process. However, regeneration of the capture solvent can potentially also be achieved by an electrochemical process. The CO2 rich solvent is sent directly to the electrolyser in which the CO2 is converted into carbon products and simultaneously creates a CO2 lean solvent at the outlet that is suitable for a new CO2 capture cycle. This dissertation studies the feasibility of integrating CO2 capture with electrochemical conversion. This is done by looking at two different pathways using two different solvents. The first pathway investigates the use of an organic solvent and the second pathway uses a (bi)carbonate solvent. This dissertation addresses different challenges related to the effective electrochemical CO2 conversion for these two different solvents and provides a perspective on the feasibility of integrating CO2 with electrochemical conversion.