Self-Nitrogen-Doped Porous Biocarbon from Watermelon Rind: A High-Performance Supercapacitor Electrode and Its Improved Electrochemical Performance Using Redox Additive Electrolyte

摘要

Self-nitrogen-doped biocarbons are obtained from the watermelon rind via an easy one-step pyrolysis-activation process. Porous biocarbon AC(W)-2, obtained with a watermelon/potassium hydroxide (KOH) mass ratio of 1:2 at 700 degrees C, exhibits a large specific surface area of 1303.3 m(2) g(-1) and is decorated with abundant nitrogen/oxygen-containing functional groups. When AC(W)-2 is used as a supercapacitor electrode, a high specific capacitance of 260 F g(-1) is achieved at a current density of 1 A g(-1). AC(W)-2 also exhibits an ultrahigh cycling stability, and its retention rate is maintained at 93.8% even after 5000 cycles at a scan rate of 100 mV s(-1). Furthermore, AC(W)-2 acquires a supramaximal specific capacitance (852 F g(-1)) and a high energy density (12.9 Wh kg(-1)) when p-phenylenediamine redox additive is added into the KOH electrolyte. Therefore, the watermelon rind can be used as a promising biomass precursor, and the as-prepared porous biocarbon is expected to be an outstanding comprehensive electrode material for electrochemical supercapacitors.