Preparation of Carbon Electrode Material with a Large Specific Surface Area and Multiscale Pore Structure from Biowaste Kochia for Symmetrical Supercapacitor
Kai Fan, Xiping Lei, Junzhan Zhang, Ting Yu, Haonan Chen, Jing Liu
Abstract
Kochia that is used as Chinese herbal medicine is always abandoned as a biowaste after extracting useful components. However, the richness of lignocellulose and the natural tubular structure make it a potential source of biomass carbon. After high‐temperature pyrolysis at 800 °C and further etching by proper activation conditions, a graded porous structured carbon‐based supercapacitor electrode material (KAC‐5) can be obtained. The electrode material is prepared in a 1:5 carbon‐to‐base ratio, possessing a specific surface area of 1441.30 m 2 g −1 , and a graded macro‐meso‐micro structure that is rich in micropores. The capacitance retention retains at 90.31% even after 10 000 cycles in 6 m KOH electrolyte and exhibits outstanding capacitance performance with a specific capacitance of 284 F g −1 at a current density of 1 A g −1 . The symmetrical supercapacitor is assembled with KAC‐5 and also has good cycling stability in 6 m KOH aqueous electrolyte, reaching 88.83% after 10 000 cycles with an energy density of 12.3 Wh kg −1 at a power density of 300 W kg −1 . Based on the above, sustainable preparation of energy storage material from waste biomass for high capacitance and stable biomass‐based supercapacitors has been achieved.