Preparation of high performance supercapacitors with nitrogen and oxygen self-doped porous carbon derived from wintersweet-fruit-shell

In this work, seedless wintersweet-fruit-shell was selected as carbon precursors, carbonized and labeled as WFC. WFC was activated by different proportions of KOH, the product was denoted as WFC-X (X = 1, 2, 3, 4 stand for the mass ratio between KOH and WFC). The morphology and structure of WFC and WFC-X were characterized by SEM and TEM. The crystallization of different materials were characterized by XRD and Raman.The electro-chemical properties of WFC and WFC-X were investigated by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. Among these materials, WFC-2 has the best electrochemical per-formance. It has the largest specific surface area (1489.31 m2 g- 1). The specific capacitance of WFC-2 can achieve 433 F g- 1, it has a capacitance retention rate of 95.20% after 5000 charge and discharge cycles. In order to more comprehensively test the electrochemical performance of WFC-2, a symmetrical supercapacitor was assembled using WFC-2. The assembled WFC-2//WFC-2 symmetric supercapacitor has been tested in 6 M KOH and 1 M Na2SO4 as the electrolyte. When the power density is 350 W kg-1, the energy density can get 14.07 Wh Kg-1 in 6 M KOH electrolyte. The symmetric supercapacitor has a capacitance retention rate of 92.36% and a coulomb efficiency of 96.55% after 5000 charges and discharges. At 1 M Na2SO4 electrolyte, when the power density is 500 W kg-1, the energy density can reach 8.33 Wh Kg-1. The symmetric supercapacitor has a capacitance retention rate of 92.44% and a coulomb efficiency of 98.11% after 5000 charge and discharge cycles. WFC-2 may be a good electrode material for supercapacitor due to its excellent electrochemical properties.

Automated summary

In this study, seedless wintersweet-fruit-shell was used as a carbon precursor for the production of activated carbon labeled as WFC. Different proportions of KOH were used to activate WFC, resulting in WFC-X (X = 1, 2, 3, 4 representing mass ratios of KOH to WFC). The morphology, structure, and crystallization of WFC and WFC-X were characterized using SEM, TEM, XRD, and Raman. The electrochemical properties of WFC and WFC-X were investigated, with WFC-2 showing the best performance. It exhibited a high specific surface area (1489.31 m2 g-1) and a specific capacitance of 433 F g-1, retaining 95.20% capacitance after 5000 charge and discharge cycles. WFC-2 was assembled into a symmetrical supercapacitor, which demonstrated high capacitance retention rate and coulomb efficiency after 5000 cycles in different electrolytes. WFC-2 shows promise as an electrode material for supercapacitors due to its excellent electrochemical properties.