Low energy carbon capture via electrochemically induced pH swing with electrochemical rebalancing

This paper demonstrates a carbon capture system using pH swing cycles driven by the proton-coupled electron transfer of DSPZ molecules. Electrochemical reduction of DSPZ increases hydroxide concentration, absorbing CO2; oxidation consumes hydroxide, releasing CO2. The electrical work for CO2 separation from a binary mixture with N2 (at CO2 inlet partial pressures of 0.1–0.5 bar, released to a pure CO2 exit stream at 1.0 bar) was measured at current densities of 20–150 mA cm−2. The work for separating CO2 from a 0.1 bar inlet to a 1 bar exit is 61.3 kJ molCO2−1 at 20 mA cm−2. Extrapolating to a 0.4 mbar inlet, the molar cycle work is 121–237 kJ molCO2−1 at 20 mA cm−2. An electrochemical rebalancing method extends cell lifetime by recovering the initial electrolyte composition after side reactions.

Shijian Jin, Min Wu, Yan Jing, Roy G. Gordon, Michael J. Aziz