Faradaic Electro-Swing of pH for Electrochemical Regeneration of Amine Sorbents for CO2 Capture.

Electrochemical approaches for sorbent regeneration in amine-based CO2 capture have emerged as promising alternatives to conventional thermally driven processes, as they enable operation under mild conditions possibly using renewable electricity. Most electro-swing processes rely on redox-active mediators that are vulnerable to side reactions and stability issues. Herein, we investigate mediator-free electrochemical pH-swing strategies based on Faradaic electrode reactions for the regeneration of amine sorbents. Nanostructured TiO2 electrodes with a capability for proton insertion and release enable reversible pH modulation in amine solution and regeneration of the sorbent. However, the extent of amine regeneration is constrained by the proton-storage capacity of the electrode. To resolve this limitation, a conversion-type Bi/BiOCl redox reaction is employed in the system, where protons are directly generated and consumed during electrochemical cycling. Although this strategy requires the presence of chloride ions in the electrolyte, significantly increased pH-swing capacity and enhanced amine regeneration are achievable. These results demonstrate the feasibilities of Faradaic electrode reactions for the regeneration of the sorbents in amine scrubbing process, which is the current state-of-the-art technology with scalability.