A modified molten-salt method to prepare graphene electrode with high capacitance and low self-discharge rate

Graphene is known to suffer from severe aggregation and incomplete recovery of a π–π conjugated system during the reduction process from graphene oxide. Here we report that these issues can be addressed by using a modified molten salt system. The advantages of the molten salt for reducing graphene show in three aspects: (i) prevent restacking; (ii) restore the conjugated network; (iii) serve as reaction medium for KNO3 activation and nitrogen doping. The molten-salt method-derived graphene (MNG) displays a highly sp2–hybrid constitution, nitrogen doping and hierarchically porous structure. With this design, the MNG–based supercapacitor manifests outstanding specific capacitance (234 F g−1 and 130 F g−1 in 6 M KOH and EMIMBF4 electrolyte, respectively), high power density, combined with excellent cycling stability and low self-discharge rate. The facile and scalable features of this strategy will be helpful for the rational design of functionalized graphene-based materials for diverse applications.