Reduced graphene oxide (RGO) is functionalized with glucose and nickel oxide for the supercapacitor application. The RGO layers intercalated by glucose create microspores inside the composite after thermal treatment at 500 degrees C, and the addition of nickel oxide reduces impedance of the composite, resulting in synergetic effects on the supercapacitor performance. That is, the specific capacitance of the composite is about five times higher than that of the RGO which has no glucose nor nickel oxide. The ternary composite also exhibits high performance of electric double layer capacitor (EDLC) and maintains the same specific capacitances up to 5,000 cycles, providing excellent cyclic stability. The ternary composite of the high EDLC performance, therefore, could be a good candidate of the supercapacitor electrodes. (C) 2015 Elsevier Ltd. All rights reserved.