Carbon materials derived from biomass are promising electrode materials for supercapacitor application due to their specific porosity, low cost and electrochemical stability. Herein, a hierarchical porous carbon derived from corncob was developed for use as electrodes. Benefitting from its hierarchical porosity, inherited from the natural structure of corncob, high BET surface area (1471.4 m²·g-1) and excellent electrical conductivity, the novel carbon material exhibited a specific capacitance of 293 F·g-1 at 1 A·g-1 in 6 M KOH electrolyte and maintained at 195 F·g-1 at 5 A·g-1. In addition, a two-electrode device was assembled and delivered an energy density of 20.15 Wh·kg-1 at a power density of 500 W·kg-1 and an outstanding stability of 99.9% capacitance retention after 4000 cycles.
Keywords: KOH activation; biowaste; hierarchical porous carbon; symmetric supercapacitor.