Membrane-separated electrodes enable high-rate low energy electrochemical carbon capture

Electrochemical carbon dioxide (CO2) capture using supercapacitive systems is emerging as a green CO2 capture technology, but its performance is currently limited by low uptake rates and high energy requirement. Here, we present a membrane-integrated supercapacitor system that addresses these challenges by decoupling electrode environments with a cation exchange membrane. This configuration sustains a high concentration of hydroxide ions at the gas-facing cathode, generated through dynamic water dissociation within the electric double layer. The resulting localized alkaline interface enhances CO2 capture by driving its conversion into (bi)carbonate species via a pH-swing mechanism. The system achieves a CO2 uptake of up to 893 millimoles of CO2 per kilogram cathode, a capture rate of 1,281 millimoles of CO2 per kilogram cathode per hour, and an energy requirement as low as 32 kJ per mole of CO2, maintaining stability over 200 hours. These findings establish a robust and scalable platform for electrochemical CO2 capture and underscore the importance of localized chemical environments in supercapacitive gas sorption systems.