Abstract
Self‐nitrogen‐doped biocarbons are obtained from the watermelon rind via an easy one‐step pyrolysis‐activation process. Porous biocarbon ACW‐2, obtained with a watermelon/potassium hydroxide (KOH) mass ratio of 1:2 at 700 °C, exhibits a large specific surface area of 1303.3 m2 g−1 and is decorated with abundant nitrogen/oxygen‐containing functional groups. When ACW‐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. ACW‐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, ACW‐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.
Funding Information
  • Natural Science Foundation of Fujian Province (2016J01729)

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