UC Irvine

The development of carbon dioxide capture and concentration technologies is vital to mitigate anthropogenic carbon dioxide emissions. Nearly all of the illustrative mitigation pathways to decarbonization depend upon CO2 capture. Current state-of-the-art technologies for carbon capture are predominantly thermal based. However, the practical applications of this technology have been limited by low overall energetic inefficiency due to Carnot limitations and thermal sorbent degradation. Electrochemical CO2 capture and concentration has been presented as an alternative technology that may address the concerns of energetic efficiency by bypassing the need for temperature swings and instead using more energetically-efficient redox swings. A fully reversible system would fully reform the sorbent, further addressing the concerns of thermal degradation. This dissertation describes the investigation and implementation into organic and inorganic redox carriers for CO2 capture and concentration. Chapter 1 describes electrochemical CO2 capture and concentration (eCCC) topics, with a specific focus on systems that utilize redox carrier species. Relevant equations and thermodynamic considerations for efficient eCCC process are discussed in detail. Additionally, reported examples of eCCC systems utilizing redox carriers are discussed and evaluated. Chapter 2 discusses a computational and experimental approach to tuning the CO2 binding affinity and reduction potential required for forming the CO2-reactive species of quinones functionalized with electron withdrawing and electron donating groups. Chapter 3 delves into investigations on the effect of supporting electrolyte on the CO2 binding affinity and reduction potential of various quinones, using Lewis acids and cation size to investigate their effects on the reduction potential of the dianion and the CO2 binding affinity. Chapter 4 describes investigations on a cobalt macrocycle and a metal-supported quinone that are both capable of CO2 capture and concentration. Chapter 5 introduces a new redox carrier, the benzoquinone di-imine, and is an experimental study on the effect of functionalization of the pendant redox-active amine. Chapter 6 describes investigations of intermolecular and intramolecular interactions and the effects they have on the reduction potential of the dianion and the CO2 binding affinity. The appendix features a detailed discussion of the reactor design used for electrochemical cycling experiments.