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Carbon capture driven by renewable electricity represents a promising approach to mitigate carbon dioxide (CO 2 ) 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 CO 2 from a dilute feed upon electro-reduction via a nucleophilic addition reaction and release a concentrated CO 2 product stream upon oxidation. However, there is a lack of quantitative understanding of the reaction kinetics landscape of redox-active CO 2 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 CO 2 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 CO 2 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 orthoisomers 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.

The complexation and decomplexation of CO2 with a series of quinones of different basicity during electrochemical cycling in dimethylformamide solutions were studied systematically by cyclic voltammetry. In the absence of CO2, all quinones exhibited two well-separated reduction waves. For weakly complexing quinones, a positive shift in the second reduction wave was observed in the presence of CO2, corresponding to the dianion quinone-CO2 complex formation. The peak position and peak height of the first re-duction wave were unchanged, indicating no formation of complexes between the semiquinones and CO2. The relative heights of both reduction waves remained constant. In the case of strongly complexing quinones, the second reduction wave disappeared while the peak height of the first reduction wave approximately doubled, indicating that the two electrons transferred simultaneously at this potential. The observed voltammograms were rationalized through several equilibrium arguments. Both weakly and strongly complexing quinones underwent either stepwise or concerted mechanisms of oxidation and CO2 dissociation depending on the sweep rate in the cyclic voltammetric experiments. Relative to stepwise oxidation, the concerted process requires a more positive electrode potential to remove the electron from the carbonate complexes to release CO2 and regenerate the quinone. For weakly complexing quinones, the stepwise process corresponds to oxidation of the uncomplexed dianion and accompanying equilibrium shift, while for strongly complexing quinones the stepwise process would correspond to the oxidation of mono(carbonate) dianion to the complexed semiquinone and accompanying equilibrium shift. This study provides a mechanistic interpretation of the interactions that lead to the formation of quinone-CO2 complexes required for the potential development of an energy efficient electrochemical separation process and discusses important considerations for practical implementation of CO2 capture in the presence of oxygen with lower vapor pressure solvents.