Abstract
In this study, corncob was explored as a low-cost and abundant precursor for the preparation of activated carbon via carbonization and the KOH activation method. The alkaline/biochar ratios varied from 3:1 to 5:1, and the activation temperatures ranged from 700 to 900 °C. The characterized results reveal that the alkaline/biochar ratios and activation temperatures had a remarkable influence on the morphology and microstructure of as-prepared activated carbon (CAC(T-R)). The CAC(T-R) presented a porous structure with a large number of micropores and a small number of mesopores. The reasonable distribution of micropores and mesopores endows the ideal structure for ion transfer and charge storage. The optimal sample CAC(700-4) exhibited the best capacitive performance with a specific capacitance of 260 F/g at 1 A/g. Moreover, the assembled CAC(700-4)//CAC(700-4) symmetric supercapacitor showed a high energy density of 14.3 Wh/kg at a power density of 250 W/kg in 6 M KOH electrolyte. It also has a capacitance retention of 95.5% after 10,000 cycles, indicating its excellent cycle stability. These results indicate that corncob-derived activated carbon provides the possible application of biomass waste in high-performance supercapacitors.