Impacts of Supercapacitor Electrode Structure on Electrochemical CO2 Capture

Supercapacitors are emerging as energy-efficient and robust devices for electrochemical CO2 capture. However, the impacts of electrode structure and charging protocols on CO2 capture performance, including the stability and CO2 selectivity over O2, remain unclear. Therefore, this study develops structure-property-performance correlations for supercapacitor electrodes at different charging conditions. We find that electrodes with large surface areas and low oxygen functionalization generally perform best, while a combination of micro- and meso-pores is important to achieve fast CO2 capture rates. With these structural features and tunable charging protocols, YP80F activated carbon electrodes show the best CO2 capture performance with a CO2 capture rate of 350 mmolCO2 kg–1 h–1 and a low electrical energy consumption of 18 kJ molCO2–1 at 300 A kg–1 under CO2, together with a long lifetime over 12000 cycles at 150 A kg–1 under CO2 and excellent CO2 selectivity over N2 and O2. Operated in a “positive charging mode”, the system achieves excellent electrochemical reversibility with Coulombic efficiencies over 99.8% in the presence of approximately 15% O2, alongside stable cycling performance over 1000 cycles. This study paves the way for improved supercapacitor electrodes and charging protocols for electrochemical CO2 capture.