Supercapacitive CO₂ Capture through a Scalable, Aqueous, Neutral Polymer-Based Electrolyte

Aqueous electrolytes offer a safer, more cost-effective, and scalable solution for electrochemical CO₂ capture. Herein, electrolytes that combine harmless polyethylene glycol with slightly salty water are developed, which enables the capture of CO₂ in a supercapacitor cell of up to 79 mmol of CO₂ per kilogram of electrode material while operating at a current density of 30 mA g^-1, a voltage of 2.5 V, at 40 °C, and under neutral pH conditions. Interestingly, applying negative charge protocols up to -2.5 V increases the amount of CO₂ adsorbed per kilogram of electrode to 356 mmol. This is attributed to both the ejection of preadsorbed bicarbonate species from the pores and their slow migration kinetics near the electrode exposed to CO₂ gas toward the positively charged counter electrode. This finding indicates that the CO₂ capture and release mechanism exhibits no dependence on the direction of the charge. These polymer electrolytes lead to a threefold increase in the gravimetric energy stored compared to similar devices operating at ≈1 V that utilize microporous carbon electrode materials. The system also reveals excellent stability and corrosion resistance under long-term cycling at high voltages. This advanced technology marks a major advancement in sustainable carbon capture solutions.