Hierarchically porous carbon derived from tobacco waste by one-step molten salt carbonization for supercapacitor

High-performance carbon materials were prepared via a one-step molten salt carbonization of tobacco waste used as electrode materials for supercapacitors. Carbon material prepared by carbonization for 3 h in molten CaCl2 at 850 °C exhibits hierarchically porous structure and ideal capacitive behavior. In a three-electrode configuration with 1 mol L−1 H2SO4 aqueous solution, it delivers specific capacitance of 196.5 F g−1 at 0.2 A g−1, energy density of 27.2 Wh kg−1 at 0.2 A g−1, power density of 983.5 W kg−1 at 2 A g−1, and excellent cyclic stability with 94% capacitance retention after 5000 charge–discharge cycles at 1 A g−1. Moreover, in a symmetrical two-electrode configuration with 6 mol L−1 KOH aqueous solution, it delivers specific capacitance of 111.1 F g−1 at 0.2 A g−1, energy density of 3.8 Wh kg−1 at 0.2 A g−1, and power density of 482.0 W kg−1 at 2 A g−1. The relationship between hierarchically porous structure and capacitive performance is also discussed.