Non-Equilibrium CO₂ Regeneration from Sorbent Materials

Direct air capture requires a technology that reduces atmospheric carbon dioxide (CO₂) levels by removing CO₂ directly from the air. One method employs the use of sorbents, which are materials designed to selectively and efficiently bind CO₂ molecules. A crucial aspect is the need to regenerate these sorbents, i.e., release the CO₂ molecules from the sorbents for further processing or storage. In this work, plasma-based regeneration is investigated using a customized flow reactor coupled to a dielectric barrier discharge. The concentration of CO₂, CO, and other products is monitored ex-situ with a residual gas analyzer. Results show that atmospheric plasma is capable of regenerating CO₂ from sorbent materials, i.e., metal carbonates. The operating temperature is adjusted from room temperature to 450K, far below the carbonate decomposition temperature used in purely thermal methods. We also show that the bath gas that is used has a critical effect on the CO₂ yield. In nitrogen or oxygen plasmas, the CO₂ yield is orders of magnitude lower than that in air plasmas. Future work includes evaluating the energy efficiency, adding catalysts to further lower the regeneration barrier, and developing and validating the reaction mechanisms.