Traditional carbon capture processes require large amounts of energy to regenerate the solvents used. Recent research has proposed to decrease the energy requirements of this process by integrating the system of carbon capture and electrochemical conversion, removing the need for the traditional regeneration step. The integration of these two steps involves the use of the same medium for both the carbon capture solvent and for the electrolyte for electrochemical conversion of the captured CO2. The proposed methodology takes advantage of the inherent elevated temperatures resulting from ohmic losses in the electrochemical system, especially at an industrial scale and helps optimize the efficiency of the conversion process. This study investigates the use of non-aqueous solutions of 1:4 choline chloride to ethylene glycol coupled with monoethanolamine as the medium for this process, particularly focussing on its use as the catholyte in this system. Specifically, this project targets the production of carbon monoxide using silver cathodes in small laboratory scale compact H-cells, with an anolyte of 0.5 M sulphuric acid and a Nafion-117 cation exchange membrane separating the compartments. Different operating conditions, including pulsed electrolysis, are utilised to attempt to modify the levels of carbon monoxide production and stabilise the system for long term operation.
Initial investigations into this system found that carbon monoxide could successfully be produced at constant reduction potentials vs. Ag/AgCl of -1.5 V and -1.7 V for approximately 10 minutes of operation when operating at 65 °C. Pulsed electrolysis has been proven to be able to increase the stability of carbon monoxide production for up to an hour of operation. The study found that the most promising conditions for the pulsed electrolysis are using positive anodic potentials vs. Ag/AgCl of either + 0.1 V or + 1.5 V for between 5 and 40 seconds in combination with cathodic potentials vs. Ag/AgCl of - 1.5 V. The faradaic efficiency of carbon monoxide production was able reach up to 24 % for one hour of operation with relatively stable production profiles when using pulsed electrolysis.
The results of this project show that this system can produce the desired carbon dioxide reduction reaction and with the use of pulsed electrolysis this can be achieved for at least one hour with faradaic efficiencies of carbon monoxide production greater than 20%. These findings showed a better overview for the next stage of this research. In particular, further work involving longer term operation of the cells is of interest after this research.

Increasing CO₂ concentration in the atmosphere has caused significant concern, paving the way to research and develop technologies like capture carbon and storage (CCS) and carbon capture and utilization (CCU). This thesis focuses on extracting CO₂  from Chimney stacks and regenerating the solvent using electrochemistry. The main aim of this thesis is to identify a solvent that is capable of being used as a good CO₂ capture medium and at the same time as an electrolyte for CO₂ reduction.
Deep eutectic solvents (DES) have been gaining much attention due to their desirable properties such as biodegradability, low vapour pressure, and high tunability for the required purpose. Research has shown promising results in the application of DES in the field of CO₂ capture at a lower price with more eco-friendly solvent. Choline chloride is the most widely used quaternary amine salt which has all the desirable properties; when combined with a CO₂ philic hydrogen bond donor group such as amines, a novel solvent could be formed. The low/negligible vapour pressure of DES makes it suitable for CO₂ absorption in industrial applications. Based on the literature, three different solvents were selected, Choline chloride and Ethylene glycol (ChCl:EG), Choline chloride and Monoethanolamine (ChCl:MEA) and Choline chloride with Aminomethyl propanol (ChCl:AMP).
Various experiments were conducted on different molar ratios of selected solvents to determine the physico-chemical properties. Viscosity was measured as it affects the CO₂ absorption capacity due to limiting the mass transfer and has a significant impact on ion mobility resulting in high ohmic drops and reduced efficiency of the electrochemical extraction process. Conductivity was also measured as having higher conductivity will reduce the ohmic drop and improve the CO₂ removal process; conductivity is inversely related to viscosity. Effect of varying temperature, water and CO₂ loading was observed on these physical properties.
Based on the experiments conducted, it was found that ChCl:EG solutions have the highest conductivity among the pure solvents, with some of the lowest viscosities. In the case of ChCl:MEA, the viscosity reduced with the increase in temperature and increased drastically on the absorption of CO₂. This is because of the formation of carbamates as confirmed by FTIR. ChCl:AMP is a unique solvent as absorption of CO₂ results in the formation of a bicarbonate precipitate, as shown in FTIR.
Addition of EG to ChCl:MEA solution improves the performance of the DES significantly. At similar CO₂ loading, the viscosity of ChCl:EG:MEA (1:4:3) is almost 63.88% less and the electrical conductivity 134.45 % more than ChCl:MEA(1:6)