A large-scale, environment-friendly method to produce water-soluble reduced graphene oxide by using glutathione as a reducing and stabilization agent has been developed. The results of UV-visible absorption spectroscopy. X-ray photoelectron spectroscopy, atomic force microscopy, and transmission electron microscopy indicate that graphene oxide is reduced to graphene nanosheets which are single-layers and exhibit good dispersion in water. A reaction mechanism is proposed. The electrochemical properties of the graphene nanosheets as electrode materials for supercapacitors are studied by cyclic voltammetry and galvanostatic charge/discharge tests. A maximum specific capacitance of 238 F g(-1) in a 1 M H2SO4 electrolyte has been obtained. Meanwhile, the material shows excellent long-term cycle stability along with the retention of 97% for specific capacitance after 1000 cycle tests. (C) 2012 Elsevier Ltd. All rights reserved.