Here, the boron-doped graphene was produced through both supercritical fluid processing as well as hydrothermal route by means of boric acid as a boron source. The availability of boron containing functional groups, quantity of B-doping as well as chemical nature were evaluated using FT-IR, EDAX and XPS analysis. The B-doped graphene synthesized via SCF processing showed 8.9 atomic % of boron while the conventional hydrothermal method showed 9.5 atomic % of boron doping. In 20% KOH solution at 1 A/g, the former displayed an enriched specific capacitance of 286 F/g and revealed a greater specific capacitance retention of 96% at 20 A/g over 10,000 cycles. To assess the performance of device, the complete cell performance was investigated in two different aqueous electrolytes. An aqueous solution of 1 M NaClO4 showed a 4 fold higher energy density of 21.2 Wh/kg compared to 5.3 Wh/kg in 20% KOH solution. Among the three different ionic liquid electrolytes, the capacitive performance is maximum in1-ethyl-3-methyl imidazolium tetrafluoroborate