Enhancing electrochemical carbon dioxide capture with supercapacitors.

Abstract

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 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 mesopores 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 capture rate of 350 mmol_CO2 kg^-1 h^-1 and a low electrical energy consumption of 18 kJ mol_CO2^-1 at 300 mA g^-1 under CO₂, together with a long lifetime over 12000 cycles at 150 mA g^-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% O_2, alongside stable cycling performance over 1000 cycles. This study paves the way for improved supercapacitor electrodes and charging protocols for electrochemical CO₂ capture.