Nitrogen-containing graphene networks with high volumetric capacitance and exceptional rate capability

Graphene has attracted more attention as advanced electrodes for supercapacitors due to its unique geometry structure and outstanding physicochemical property. But its low specific capacitance, especially low volumetric capacitance, has greatly restricted the practical application of graphene electrode materials. Herein, we synthesized nitrogen-containing graphene networks by using 2, 3-diaminopyridine (O-DAP) as functional agent in a facile hydrothermal route. During the hydrothermal process, not only the pyrrolic-N, but also the pyrazine-N is produced in the graphene lattice at the edge/defect site of graphene because of the double -NH2 in DAP reactant. Owing to the high nitrogen content (17.5 at%), special nitrogen configuration, and high density (1.66 g cm(-3)), the N-containing graphene networks present high gravimetric capacitances up to 353 F g(-1) and high volumetric capacitances over 586 F cm(-3) in 1 M H2SO4 electrolyte. More remarkably, the N-containing graphene electrodes exhibit exceptional rate capability with a capacitance retention of 80.6% at a high current density of 20 A g(-1) and good cycling stability of 91.5% retention after 5000 cycles in a symmetrical two-electrode configuration. (C) 2019 Elsevier Ltd. All rights reserved.