We demonstrate a carbon capture system based on pH swing cycles driven through proton-coupled electron transfer in aqueous-soluble organic molecules. Electrochemical reduction causes an increase of hydroxide concentration, which absorbs CO2; subsequent electrochemical oxidation of the reduced molecule consumes the hydroxide, causing CO2 outgassing. The ideal cycle work and the measured electrical work of separating CO2 from various gas mixtures are evaluated. The ideal cycle work varies from 16 to 75 kJ molCO2-1 as throughput per cycle increases, with the potential to go substantially lower if CO2 capture or release is performed simultaneously with electrochemical reduction or oxidation. At the time of submission of this abstract, the measured work for separating CO2 from an inlet of 0.1 bar CO2 + 0.9 bar N2, inlet and concentrating into a 1 bar pure CO2 exit is 61.3 kJ molCO2-1 at a current density of 20 mA cm-2. We also report an electrochemical rebalancing method that extends cell lifetime by recovering the initial electrolyte composition after it is perturbed by side reactions. We discuss the implications of these results for future low-energy electrochemical carbon capture devices.

pH swing cycle for carbon capture electrochemically driven through proton-coupled electron transfer

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.