Constructing the quinonyl groups and structural defects in carbon for supercapacitor and capacitive deionization applications

Abstract

The structural defects and oxygen-containing functional groups of carbon materials as electrode materials for supercapacitors or capacitive deionization devices are critical to their electrochemical performance. The tuning of surface oxygen-containing functional groups and carbon defects during pyrolysis is key to achieve a high performance in ion storage. Herein, quinonyl-dominant defective porous carbon is prepared by a pyrolysis and cross-linking route using lavender stem and potassium acetate as precursor. Benefiting from the presence of abundant defect and surface quinonyl groups, porous carbon shows an ultra-high specific capacitance of 401 F g^-1 (1 A g^-1) and a high capacitance retention of 63% at a high current density of 100 A g^-1 in a KOH solution. Meanwhile, as a capacitive deionization electrode material, it also exhibited a high adsorption capacity of 25.5 mg g^-1 in 500 mg L^-1 NaCl solution at 1.2 V. Theoretical density functional theory (DFT) calculation demonstrates that surface quinonyl groups and carbon defects can synergistically facilitate the adsorption of K⁺ and Na⁺ during the charge/discharge process. This work provides a new perspective for understanding the role of surface oxygen-containing groups and intrinsic defects of porous carbon materials in electrochemical energy storage and desalination applications.

Keywords: Capacitive deionization; Defective carbon; Quinonyl group; Supercapacitor.