Reduced graphene oxides have been prepared via controllably thermal and chemical reduction processes. The structure, surface chemistry and electrochemical behaviors of reduced graphene oxides are investigated by Raman spectroscopy, N-2 adsorption, temperature-programmed desorption, Fourier-transform Infrared spectroscopy, X-ray photoelectron spectroscopy, as well as charge/discharge measurements. The enhanced reversible capacity of reduced graphene oxides is attributed to specific functionalities rather than to exceptional large specific surface area or structure defect. The contributed capacities at potential higher than 1.5 V and in region of 0.8-1.5 V are attributed dominantly to phenol groups and cyclic edge ether groups, respectively. These findings may be beneficial to the material design of graphene-based anode materials with high energy density. (C) 2013 Elsevier B.V. All rights reserved.