Doping of heteroatoms on graphene networks is an efficient way of modifying both, chemical and electrochemical properties of graphene. Here, the preparation of boron doped graphene was achieved by supercritical fluid processing using sodium tetraborate as a boron source. The phase purity, structure and surface morphology of all the prepared materials were characterised by XRD, Raman spectra, FE-SEM and HR-TEM. The presence of boron bearing functionalities and type of B-doping are determined by FT-IR spectroscopy and XPS, respectively. From the different weight combination of B-source along with graphene oxide, the B-doped graphene obtained from B-source and graphene oxide are in 1 : 2 weight ratio showed an enhanced capacitive behaviour over reduced graphene oxide with an improved specific capacitance value of 270 F/g at 1 A/g and revealed a superior cycling stability of 93 % retention over 10000 cycles at 10 A/g. To appreciate the device performance, the full cell studies was performed in three different electrolytes and the energy density obtained using 1ethyl-3-methyl imidazolium tetrafluoroborate (EMIMBF 4 ) as ionic liquid electrolyte is found to be 39.3 Wh/kg which is higher than both 20 % KOH solution (5.1 Wh/kg) and 1 M TEABF 4 in acetonitrile (18.6 Wh/kg).[a] S.