One-pot synthesis of porous carbon from Chinese medicine residues driven by potassium citrate and application in supercapacitors

Traditional methods of the disposal of Chinese medicine residues typically waste resources and are unable to resolve environmental issues caused by residue stacking. Herein, a one-pot synthesis of porous carbon (CKs) for supercapacitor applications is developed using licorice residues to achieve its added values. The formation of CKs is influenced by both the pyrolysis temperature (600–800 °C) and activation of potassium citrate, which etches pores on biochar derived from licorice residues and induces the formation of nanoflower-like hierarchical porous carbon. The use of CK-600 as a negative electrode material in a three-electrode system resulted in an outstanding specific capacitance of 221 F g−1 at 0.5 A g−1, 82 % capacity retention even at 10 A g−1, and long-term stability. The assembled symmetric supercapacitor CK-600//CK-600 device delivered a high energy density (7.57 Wh kg−1). Porous carbon produced through a simple one-step pyrolysis is a promising electrode material for supercapacitors, thereby enhancing the comprehensive value of Chinese medicine residues.