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

Electrochemical carbon dioxide (CO₂) capture using supercapacitive systems is a promising green technology but remains 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 high hydroxide concentration at the gas-facing negative electrode, 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 mmol/kg with a fast rate of 1281 mmol/kg/hour at -1.4 V under 20% CO₂. Energy consumption as low as 32 kJ/mol is obtained at -0.8 V under 20% CO₂ together with a long lifetime over 200 hours at -1.0 V, 10% CO₂. These findings establish a robust platform for electrochemical CO₂ capture and underscore the importance of localized chemical environments in supercapacitive swing adsorption.