We are exploring the direct air capture of CO₂ by mimicking crucial functions of single cell organisms that enable selective and kinetically efficient uptake under the small thermodynamic driving force created by low partial pressures of CO₂ in the atmosphere. We hypothesize that by tuning the bindign affinity of the amines of a CO₂ caputre solvent and functionalized electrodes, we can facilitate CO₂ delivery to a redox site where it can be bound and transiently stored under a bias and easily released by a pH swing or removal of bias. Our current project strives to achieve this by utilizing a CO₂ selective membrane (the ionone polymer membranes developed at U. Alabama to remove H₂O, O₂ and N₂), kinetically coupled to a CO₂ capture solvent (designed by PNNL) for enhanced uptake selectivity and favorable transport and an electrochemically generated transient site for strong binding and reversible conversion to carbonates/bicarbonates (Figure 1). We are taking a holistic approach to overcome the thermodynamic/kinetic limitations imposed by the low driving force for CO₂ uptake, successively increasing CO₂ sorption to create a free energy gradient to funnel CO₂ towards a strongly binding electrochemically generated active site. Conversely, the extensive energy penalties for CO₂ release can be mitigated by either electrochemical switching or a pH swing, the latter of which opens the potential for a high throughput flow system.

Figure 1. DAC using a capture solvent as a first stage adsorber and an electrode as a second-stage adsorber that can be switched off for facile CO<sub>2</sub> release.

Figure 1. DAC using a capture solvent as a first stage adsorber and an electrode as a second-stage adsorber that can be switched off for facile CO₂ release.

Asanga Padmaperuma

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