Microwave-Assisted Preparation of Hierarchical N and O Co-Doped Corn-Cob-Derived Activated Carbon for a High-Performance Supercapacitor

Microwave (MW) treatment was reported as an efficient method to prepare porous carbon-based electrode material with high capacity for a high-performance supercapacitor. Herein, the superiority of the mechanism of MW treatment was tried to be revealed by preparing a N and O co-doped porous activated carbon (MWAC) based on a heteroatom-rich corn cob and compared to that of the conventional heating method. The resulting MWAC has a large specific surface area of 2508 m2/g with hierarchical micro- and mesoporous structures and abundant heteroatom doping of O and N. In a three-electrode system, the MWAC shows a superior specific capacitance of 560 F/g at a discharge current density of 0.5 A/g in a 6 mol/L KOH aqueous electrolyte. The symmetric supercapacitor fabricated by MWAC electrodes in a 6 mol/L KOH electrolyte shows excellent capacity retention of 96.8%, even after 10 000 galvanostatic charge–discharge cycles at the current density of 1 A/g. The aqueous (6 mol/L KOH) symmetric supercapacitor delivers a high energy density of 9.24 Wh/kg at a power density of 250 W/kg. The results prove that the MW heating shows more superiority in retaining inherent heteroatoms and creating hierarchical micro- and mesoporous structures of activated carbon for supercapacitors with high performance.