Extrusion plant microtube synthesis of micron-sized nitrogen-doped hollow porous carbon nanosheets for high rate and high energy density supercapacitors

Hollow carbon nanosheets with predominant mesopores have been demonstrated as a promising electrode material for supercapacitor, but their low specific surface area with relatively low micropore proportion limits their specific capacitance and energy density. Herein, we develop a novel extrusion plant microtube strategy to synthesize micron-sized nitrogen-doped hollow porous carbon nanosheets (MNHPCS) from dandelion fluff having the specific natural thin-wall and hollow tubular bundled structure through high-pressure extrusion, carbonization and KOH activation. The optimized MNHPCS displays strutted bilayer nanosheet structure, large SSA of 1593 m2 g-1, high micoporosity of 71.2 % and high heteroatom content (5.2 at.% for N, 7.0 at.% for O). Importantly, MNHPCS prepared by the new technique overcomes the drawbacks of hollow carbon nanosheets and presents an excellent capacitance of 378 F g-1 at 0.5 A g-1 and rate capability of 57 % at 80 A g-1 in 6 M KOH. Furthermore, the energy density of MNHPCS//MNHPCS based supercapacitor in EMIMBF4 can reach up to 84 Wh kg-1. Most importantly, MNHPCS can be easily achieved from various plant wastes having hollow tubular structure, which would provide a clearly method on selecting plant precursors for producing hollow porous carbon nanosheets applied on supercapacitors.