High power density of graphene-based supercapacitors in ionic liquid electrolytes

Reduced graphene oxide (RGO) has been prepared with HBr as a reducing reagent. RGO-based supercapacitors in two-electrode systems have been fabricated in ionic liquid electrolytes of 1-butyl-3-methylimidazolium hexafluorphosphate (BMIPF6) and 1-butyl-3-methylimidazolium tetrafluoroborate (BMIBF4), respectively. RGO in BMIBF4 shows higher capacitance of 74 F g(-1) at 10 mV s(-1), while RGO in BMIPF6 merely exhibits 45 F g(-1). However, due to wider potential window of 4 V for BMIPF6. RGO in BMIPF6 has higher energy and power densities. The highest power density of 27.8 kW kg(-1) is obtained at 14 A g(-1) and the maximum energy density of 18.9 Wh kg(-1) at 1 A g(-1) for BMIPF6. The exciting results infer potential application for RGO in BMIPF6. (C) 2011 Elsevier B.V. All rights reserved.