The green and efficient synthesis of graphene using sodium carbonate (Na2CO3) as a chemical reducing agent was studied. Extensive characterization confirmed the formation of graphene from graphene oxide using a Na2CO3 solution. The C/O atomic ratio of the as-prepared graphene has increased from 2.48 to 8.15 after reduction as determined by X-ray photoelectron spectroscopy. The conductivity of as-prepared graphene sheets is as high as 10 S m(-1). After electrochemical measurements, gravimetric capacitances of 228 and 166 F g(-1) at current densities of 5 and 25 mA cm(-2), respectively, were obtained with KOH electrolyte. (C) 2013 Elsevier B.V. All rights reserved.