Poly(aniline-co-pyrrole) was coated on the surface of reduced graphene oxide (rGO) through in situ chemical oxidative polymerization of aniline and pyrrole monomers. For comparison, rGO/polyaniline (PANi) and rGO/polypyrrole (PPy) were also prepared under the similar reaction condition, respectively. The resulting nanocomposites were characterized by field-emission scanning electron microscopy, atomic force microscopy, Fourier transform infrared and Raman spectrometry, and thermogravimetric analysis. Ultrathin layers of conducting polymers on the surface of rGO not only provide more electrochemically active sites but also shorten the distance for ion and electron transport, benefiting from the existence of strong interactions between polymeric chains and rGO. Besides, rGO in the composite can also provide an electron transfer path due to its excellent conductivity and high surface area. What is more, rGO/Copolymer exhibits the highest thermal stability and superior electrochemical stability among these composites, benefiting from its specific chemical structures, intrinsic electrochemical properties of three components, and more importantly, the synergistic effect in the composite. In 1 M Na2SO4 electrolyte, the specific capacitance of rGO/Copolymer was 541 F g(-1) at the scan rate of 1 mV s(-1), and 283 F g(-1) at the scan rate of 20 mV s(-1), respectively, which is larger than those for rGO/PANi and rGO/PPy. After 500 cycles, capacitance retention was 86% for rGO/Copolymer. These demonstrate that rGO/Copolymer can be applied as a high-performance electrode material for electrochemical supercapacitors. (C) 2015 Elsevier Ltd. All rights reserved.