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.

    Abstract
    1 Introduction
    2 Experimental
        2.1 Materials and chemicals
        2.2 Carbonization process
        2.3 Preparation of electrodes and electrochemical measurements
        2.4 Characterization
    3 Results and discussion
        3.1 Morphology and structure characterization of carbon materials
        3.2 Electrochemical characterization of carbon materials
    4 Conclusions
    Acknowledgements 
    References

• Yuxuan Liu(School of Chemical and Environmental Engineering, Hubei Minzu University)
• Xinhua Cheng(School of Chemical and Environmental Engineering, Hubei Minzu University)
• Shenghui Zhang(School of Chemical and Environmental Engineering, Hubei Minzu University)