Supercritical fluid assisted synthesis of S-doped graphene and its symmetric supercapacitor performance evaluation using different electrolytes

Enhancement in supercapacitive behaviour of heteroatom doped graphene could be possible only due to redox behaviour by heteroatoms. Here, we report that the sulphur doped graphene production using supercritical fluid assisted processing using dimethyl sulfoxide and thioacetamide as sulphur precursors. The availability and the nature of S-doping were determined using elemental and XPS analysis. The electrochemical studies demonstrated that out of three different proportions of dimethyl sulphoxide and graphene oxide, S-doped graphene containing 2 wt% of sulphur achieved a specific capacitance of 261 F/g at 1 A/g and revealed a superior capacitance retention of 90% at 10 A/g from initial value over 10000 cycles. To comprehend the performance of fabricated symmetric cell, the full cell pefromance was evaluated in three different electrolytes. Among the electrolytes, EMIMBF4 (ionic liquid) electrolyte displayed enhanced energy density of 39 Wh/kg and relatively larger than 1 M NaClO4/acetonitrile (21 Wh/kg) and 20% KOH solution (4.4 Wh/kg).