Abstract
Porous active carbon electrode (PACE) materials in this work were prepared by a two-step method, which includes carbonization and KOH activation of dried lotus stalk at relatively high temperatures in an argon atmosphere. These processes produced a great number of disordered micropores and mesopores, thereby significantly increasing the specific surface area, up to 1022 m2 g−1. Those pores offered a more favorable pathway for electrolyte penetration and transportation, and thus improved the performance of supercapacitors. The electrochemical properties of PACE materials were tested in 6 M KOH electrolyte, and the results indicated that the specific capacitance reached 248.5 F g−1 at the current density of 1 A g−1. The PACE showed a rate capability with specific capacitance retained over 82.5% at a current density of 10 A g−1 and a good long-term cycling stability with the specific capacitance retained 90.6% after 5000 cycles. Meanwhile, the energy density of PACE-based supercapacitors is 34.51 Wh kg−1 at a corresponding power density of 496.94 W kg−1. Lotus stalk manifests itself as a good carbon source candidate for the development of supercapacitor devices, and the facile synthetic process has a bright future for practical applications.