Electrochemically Mediated CO2 Capture and Release via pH Swing and Adduct Formation in Flow Cells

We report full cell-cycling results for two electrochemically-mediated CO2¬ capture and release systems with newly developed redox-active molecules. Sodium 2,2'-(phenazine-1,8-diyl)bis(ethane-1-sulfonate) (1,8-ESP) captures carbon through pH swing driven by proton-coupled electron transfer, while 1,1'-bis[3-(trimethylammonio)propyl]anthroquinone dichloride (1,5-BTMAP AQ) captures carbon through CO2-adduct formation. Cyclic voltammetry, UV-Visualization, and fluorescence spectroscopy identify electrochemical and structural changes in 1,5-BTMAP AQ during carbon capture that corroborate with the CO2 adduct-formation hypothesis. Full cell bench-scale cycling studies of 1,8-ESP and 1,5-BTMAP AQ demonstrate their high capture capacity and low energetic cost. At 20 mA cm-2, CO2 capture system 0.1M 1,8-ESP with capture under 10% CO2 and release under 100% CO2 has a capture capacity of 2.0 molCO2 molRAS-1 (with 10% error) and an energetic cost of 52.46 kJ molCO2-1 at 20 mA cm-2; CO2 capture system 0.05 M 1,5-BTMAP AQ with capture under 30% CO2 and release under 100% CO2 has a capture capacity of 1.88 molCO2 molRAS-1 (with 10% error) and an energetic cost of 110.47 kJ molCO2-1 at 20 mA cm-2. The high efficiency and scalability of these systems makes them promising candidates for CO2 capture and release applications.