The majority of existing processes for the capture of carbon dioxide from flue gas or air rely on pressure or temperature swings to regenerate the sorbent. While process improvements have significantly reduced energy requirements over the years, heat integration with an existing plant adds substantial complexity and the presence of inactive components reduces efficiency. Electrochemistry can be used to directly modulate the affinity of redox-active sorbents for CO2, potentially lowering process energy requirements. Such processes would also eliminate the need for significant heat integration. Flowing systems that enable capture over large areas and desorption at a single point with electrochemistry have so far only been demonstrated in water. We investigate the applicability of liquid quinones for carbon capture, demonstrating a concept for a low volatility nonaqueous system amenable to flowing processes that could apply to other redox-active materials. Such a process could eliminate evaporative solvent loss. We demonstrate the ability of the liquid quinone to capture CO2 in its reduced state and release it upon oxidation. Coupled with a ferrocene derived counter electrolyte, and a small amount of glyme diluent, the process is shown to achieve continuous capture and release of CO2. We further demonstrate the influence of liquid flow rate and current on process energetics. This work suggests many future studies in cell and process design, and we believe will inspire novel sorbent design.

Redox-active liquid sorbent for electrochemically mediated carbon capture

ACS Spring 2022

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