High-Capacity and High-Stability Electrochemical CO2 Capture Cell with Coupled Electricity Storage

We report an electrochemical cell for CO2 capture based on pH swing cycles driven through proton-coupled electron transfer of a newly developed phenazine, 2,2'-(phenazine-1,8-diyl)bis(ethane-1-sulfonate) (1,8-ESP), which exhibits high aqueous solubility, > 1.35 M, over pH range 0.00–14.90. The system operates with a high capture capacity of 0.86–1.41 mol/L, a low energetic cost of 36.4–55.2 kJ/mol, and an extremely low capacity fade rate of < 0.01%/day, depending on organic concentration. The system charge-discharge cycle provides an electrical energy storage function that can be run efficiently only for storage when called for by electricity market conditions. These results demonstrate the great potential of electrochemically-driven pH swing cycles based on proton-coupled electron transfer of redox-active organics for CO2 capture.