Assessing the Kinetics of Quinone–CO₂ Adduct Formation for Electrochemically Mediated Carbon Capture

Abstract

Carbon capture driven by renewable electricity represents a promising approach to mitigate carbon dioxide (CO₂) emissions and combat climate change. Electrochemically mediated carbon capture can be achieved by developing redox-active Lewis bases, with quinones being the most representative chemistry. In aprotic electrolytes, a subset of quinoid species can selectively uptake CO₂ from a dilute feed upon electro-reduction via a nucleophilic addition reaction and release a concentrated CO₂ product stream upon oxidation. However, there is a lack of quantitative understanding of the reaction kinetics landscape of redox-active CO₂ sorbents, especially considering the complex nature of the multi-component electrolyte media they must be deployed in. To bridge this knowledge gap, we investigate the bimolecular reaction rate constant between CO₂ and radical anions of various quinones in a range of electrolytes using an electroanalytical technique. Combined with molecular dynamics and density functional theory calculations, we provide insights into the complex interplay between quinone chemistry, supporting salt composition, and electrolyte solvents on the intrinsic CO₂ adduct formation kinetics. To summarize some key observations, we found that the reaction rate is affected by both the identity and concentration of the cationic and anionic species in the supporting electrolyte, the presence of hydrogen-bonding additives may accelerate the kinetics, and ortho-isomers of quinones have a faster reaction rate than para-isomers. We believe the work can help guide the rational design of electrochemical microenvironments for enhanced electrochemically mediated carbon capture performance.

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