Synthesis of Nitrogen-Doped Microporous/Mesoporous Carbon with Enhanced Pseudocapacitive Behavior for High-Performance Symmetrical Supercapacitors

Hierarchical porous carbons are widely used as electrode materials for supercapacitors; however, promotion of the specific capacitance and energy density remains a challenge. Here, we design a N-doped hierarchical microporous/mesoporous carbon (NMC) fabricated through the one-step heat treatment of interpenetrating polymer networks. The pores are obtained by phase separation of the two network polymers with physical penetration and subsequent pyrolysis of the sacrificial polymers to shape the rich micropores/mesopores on the pore wall of a honeycomb-like carbon skeleton formed from carbon precursors. In particular, the optimized NMC possesses an ultrahigh specific surface area of 1969.0 m(2) g(-1) and a pore volume of 1.092 cm(3) g(-1), as well as homogeneous distribution of elemental nitrogen. The NMC also exhibits a distinguished specific capacitance of 261.6 F g(-1) at 0.5 A g(-1) and an excellent cycling stability of 100 % after 10 000 cycles in 6 M KOH in a three-electrode system. Impressively, in situ heteroatom doping of NMC effectively enhances the specific capacitance, and the proportion of pseudocapacitive performance can be as high as 25.4 % of the total capacitance. Symmetrical supercapacitors assembled with two protruding electrodes deliver a high energy density of 23.9 W h kg(-1) at 225 W kg(-1) and an outstanding cycling stability of 93 % after 10 000 cycles in 1 M Na2SO4. All of these features indicate that N-doped microporous/mesoporous carbon is a promising electrode material for supercapacitors.