Hydrothermal synthesis of macroscopic nitrogen-doped graphene hydrogels for ultrafast supercapacitor

Nitrogen-doped graphene has been a recent research focus. It is crucial to further utilize the excellent properties of graphene macroscopic assemblies. Herein, we first report a unique and convenient hydrothermal process for controlled synthesis and structural adjustment of the nitrogen-doped graphene hydrogel (GN-GH), which can be readily scaled-up for mass production of nitrogen-doped graphene hydrogel by using organic amine and graphene oxide as precursors. The organic amine is not only as nitrogen sources to obtain the nitrogen-doped graphene but also as an important modification to control the assembly of graphene sheets in the 3D structures. Inner structure of the GN-GHs and the content of nitrogen in the graphene are easily adjusted by organic amine. Interestingly, it has been found that the supercapacitor performance of the typical product could be remarkably enhanced. Even at an ultrafast charge/discharge rate of 185.0 A/g, a high power density of 205.0 kW/kg can be obtained. In addition, at a current density of 100.0 A/g, 95.2% of its capacitance was retained for 4000 cycles. The present nitrogen-doped graphene hydrogels may have potential applications as ultrahigh power density capacitors in the vehicle, lift and the other devices at high rates. (C) 2013 Published by Elsevier Ltd.