Thermodynamic Assessment of Redox-Active CO ₂ Capture Agent Performance in Aerobic Environments

Electrochemically mediated carbon capture is receiving more attention due to its modularity, low-cost, and low-energy prospects. One implementation hurdle is the undesired formation of superoxide, via oxygen reduction, over activation of the CO2 capture sorbent. Modifying the sorbent or its environment can avoid oxygen reduction, but the effect on sorbent activation has not been quantified. Here we use an equilibrium thermodynamic model to investigate the effect of shifting the reduction potentials of a generic one- or two-electron redox-active species in different system configurations. Two-stage systems, which perform sorbent activation and CO2 absorption simultaneously, anodically shift the potential where CO2 can be absorbed, which can be exploited to avoid oxygen reduction. With parameters obtained for specific quinones by density functional theory, we find that previously disregarded molecules based only on the reduction potential may be suitable candidates for electrochemically mediated CO2 capture in two-stage configurations.