We have previously shown that electrochemical CO₂ capture is possible using a pH swing cycle that is driven by proton-coupled electron transfer (PCET) involving organic molecules [1]. More recently, we have begun to consider a new design for electrochemical CO₂ capture in which PCET-active species are conformally attached to the internal surface area of a highly porous electrode, and effect a reversible pH swing in an adjacent layer of aqueous electrolyte upon redox cycling. We develop a continuum reaction-transport model that simulates reactive CO₂ capture into and release from the electrolyte layer, as well as transport of (bi)carbonate species, and protons, in response to an applied current or voltage. The model permits an assessment of the energetic cost of CO₂ separation under various current densities and concentration gradients, and decomposition of that cost into thermodynamic, kinetic, mass transport-related and Ohmic contributions. We then highlight potential pathways to achieving an energetic cost of CO₂ capture from air of 100 kJ/mol_CO2, and discuss preliminary results from an experimental prototype.

[1] Jin. S, Wu M., Gordon R., Aziz M., Kwabi D., pH Swing Cycle for CO2 Capture Electrochemically Driven through Proton-Coupled Electron Transfer