LAUSR

A rapid facile and one-pot formation of N-doped graphene by benzimidazole as a heterocyclic nitrogen source was explored by supercritical fluid technique. Here, we have investigated the electrochemical capacitance of N-doped graphene using various electrolytes. The availability of nitrogen-containing functionalities was scrutinized by FT-IR spectra. The type and quantity of N-doping were examined via elemental analysis and XPS, separately. Three various weight fractions of graphene oxide and benzimidazole were prepared. The electrochemical capacitance studies illustrated the N-doped graphene bearing 4.4 wt% of N achieved an improved capacitance of 256 F g −1 at 1 A g −1 . The capacitive behavior for the full cell using two different aqueous electrolytes was performed and revealed an energy density of 12.3 Wh kg −1 in the aqueous solution of 1 M NaClO 4 which was three times superior to 20% KOH solution (4.1 Wh kg −1 ) and in further the full cell examination in two different non-aqueous electrolytes, suggesting that the energy density accomplished in EMIMBF 4 electrolyte at 0.2 A g −1 was found to be 30 Wh kg −1 which was superior to 1 M TBABF 4 in acetonitrile (13.8 Wh kg −1 ). Graphical abstract N-doped graphene was prepared via supercritical fluid route using benzimidazole and achieved a maximum specific capacitance of 256 F g −1 at 1 A/g. The full cell studies in various electrolytes revealed that an energy density of 30 Wh kg −1 was obtained in EMIMBF 4 (ionic liquid) which is higher than both 20% KOH solution (4.1 Wh kg −1 ), 1 M NaClO 4 solution (12.3 Wh kg −1 ), and 1 M TBABF 4 in acetonitrile (13.8 Wh kg −1 ).