Hierarchical porous nitrogen-doped graphite from tissue paper as efficient electrode material for symmetric supercapacitor

Hierarchical porous nitrogen-doped graphite from tissue paper (N-ATG) is synthesized and used as symmetric supercapacitor electrode material. Electrochemical characterizations show that the N-ATG has an ultrahigh capacitance of 696 F g(-1) (473 F cm(-3)) at 0.5 A g(-1) and mass loading of 1 mg cm(-2), in 6 mol L-1 KOH solution. The capacitance retention rate is 49.6% at 80 A g(-1) from mass loading of 1 mg cm(-2) to 20 mg cm(-2). The energy densities of the N-ATG are 24.2 and 9.8 Wh kg(-1) (i.e. 16.5 and 6.7 Wh L-1) at power densities of 320 and 39831 W kg(-1) (i.e. 218 and 27085 W L-1), respectively, which rank the highest performances especially at high power densities among heteroatom-doped carbon electrodes. The N-ATG possesses ultrahigh specific surface area of 2327 m(2) g(-1), large average pore diameter of 10.3 nm, high contents of doped N (6.5 at.%), graphitized structure with 1-5 graphene layers and widened lattice distance, dense defects, and high packing density (0.68 g cm(-3)), which account for the excellent gravimetric and volumetric capacitances as well as the high rate capacity.