journal homepage: www.elsevier.com/locate/nanoenergy Available online at www.sciencedirect.com RAPID COMMUNICATION Tuning graphene surface chemistry to prepare graphene/polypyrrole supercapacitors with improved performance Linfei Lai a,b , Liang Wang a , Huanping Yang a , Nanda Gopal Sahoo c , Qian Xin Tam a , Jilei Liu a , Chee Kok Poh b , San Hua Lim b , Zexiang Shen a,n , Jianyi Lin b,nn a Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore b Institute of Chemical and Engineering Sciences, A n STAR,1 Pesek Road, Jurong Island, Singapore 627833, Singapore c Energy Research Institute at NTU (ERI@N), Nanyang Technological University, 50 Nanyang Drive, Singapore 637553, Singapore Received 18 April 2012; received in revised form 24 May 2012; accepted 25 May 2012 Available online 19 June 2012 KEYWORDS Graphene; Surface chemistry; Conducting polymer; Supercapacitor Abstract A series of functionalized graphene derived from graphite oxide (GO) and doped with polypyrrole (PPy) are prepared to systematically investigate the combined effect of surface functionalization and polymer hybridization on supercapacitor performance. Surface chemistry of graphene is found to be of significant importance to PPy growth and PPy/graphene electrochemical performance improvement. High specific capacitance has been achieved by N doped graphene/polypyrrole (NG– PPy) electrode with a value of 393.67 Fg 1 , which is larger than those of –NH 2 modified graphene/ PPy (225.33 Fg 1 ), GO/PPy (165.25 Fg 1 ), reduced GO/PPy electrodes (150.00 Fg 1 ) under the same experimental conditions. Incorporation of N into the graphene network enhances electronic transfer efficiency and improved graphene surface wettability, therefore, largest synergistic effect is achieved on NG–PPy. Introduction of N doping to carbon material before the growth of conducting polymer is essential to prepare carbon/conducting polymer composites with high cycling stability and specific capacitance for supercapacitor application. Crown Copyright & 2012 Published by Elsevier Ltd. All rights reserved. Introduction Electrochemical supercapacitors have gained intense inter- est in advanced power research field due to its high power 2211-2855/$ - see front matter Crown Copyright & 2012 Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.nanoen.2012.05.012 n Corresponding author. nn Corresponding author. E-mail addresses: zexiang@ntu.edu.sg (Z. Shen), lin_jianyi@ices.a-star.edu.sg (J. Lin). Nano Energy (2012) 1, 723–731