Covalently functionalized single-walled carbon nanotubes and graphene composite electrodes for pseudocapacitor application. Pierre Le Barny *a , Bernard Servet a , Stéphane Campidelli b , Paolo Bondavalli a , Christophe Galindo a Thales Research and Technology, Campus Polytechnique, 1 Avenue Augustin Fresnel, 91 767 Palaiseau Cedex, France; b IRAMIS, Service de Physique de l’Etat Condensé, Bât. 524, CEA Saclay, 91 191 Gif sur Yvette Cedex, France. ABSTRACT The use of carbon-based materials in electrochemical double-layer supercapacitors (EDLC) is currently being the focus of much research. Even though activated carbon (AC) is the state of the art electrode material, AC suffers from some drawbacks including its limited electrical conductivity, the need for a binder to ensure the expected electrode cohesion and its limited accessibility of its pores to solvated ions of the electrolyte. Owing to their unique physical properties, carbon nanotubes (CNTs) or graphene could overcome these drawbacks. It has been demonstrated that high specific capacitance could be obtained when the carbon accessible surface area of the electrode was finely tailored by using graphene combined with other carbonaceous nanoparticles such as CNTs 12 .In this work, to further increase the specific capacitance of the electrode, we have covalently grafted onto the surface of single-walled carbon nanotubes (SWCNTs), exfoliated graphite or graphene oxide (GO), anthraquinone (AQ) derivatives which are electrochemically active materials. The modified SWCNTs and graphene-like materials have been characterized by Raman spectroscopy, X-ray photoemission and cyclic voltammetry . Then suspensions based on mixtures of modified SWCNTs and modified graphene-like materials have been prepared and transformed into electrodes either by spray coating or by filtration. These electrodes have been characterized by SEM and by cyclic voltammetry in 0.1M H 2 S0 4 electrolyte. Keywords: graphene, graphene oxide, anthraquinone, pseudocapacitor, functionalization, SWCNT, spray-coater. 1. INTRODUCTION Developing alternative renewable energy resources has now become a global priority due to the dramatic increase in the world energy consumption. It has been estimated that the world's energy requirement would double by 2050 1 . As large fluctuations of the energy delivered are inherent in the use of sources of renewable energy, development of efficient systems for energy storage is strongly required. One of the best ways to do this, is to convert chemical energy into electrical energy. Electrochemical devices able to perform such a conversion are known as fuel cells, batteries and supercapacitors. Each storage system has a suitable application range. Thus, supercapacitors which are able to achieve higher power density and longer cycle life than batteries are used when power pulses are required (electrical/hybrid vehicles, memory back-up systems, emergency doors on Airbus A380, industrial power supplies...). Electrodes of commercially available supercapacitors also known as Electrochemical Double Layer Capacitors (EDLC) are made of activated carbon (AC). Electrolyte can be either aqueous or organic 2,3 . However activated carbon despite its high specific area (e.g. 1000-2000m 2 /g) and its low cost, suffers from some drawbacks. These drawbacks include a limited electrical conductivity and accessibility of the AC pores to solvated ions of the electrolyte and the need for a binder to ensure the expected electrode cohesion. For all these reasons, there has been a great deal of research effort aiming to replace AC by carbonaceous materials with improved physical properties. Among all the carbon-based materials, carbon nanotubes (CNTs) 4 and graphene 5-9 seem most promising. Indeed, CNTs combine a high electrical conductivity (which could reach up 10 000Sm -1 ) with a high mesoporosity (e.g. 300-400m 2 /g) thus allowing a good electrolyte accessibility. In the same manner, graphene possesses a rather high electrical conductivity 10 (in the range of 6000S/m), a large surface area (2630 m 2 /g in the case of a single graphene sheet 11 ) and outstanding mechanical properties. However, graphene suffers from a tendency to form irreversible agglomerates or to restack to form graphite through the van der Waals interactions, leading to degraded physical properties. To overcome * pierre.lebarny@thalesgroup.com Tel 33 (0)1 69 41 59 24; Fax : 33 (0)1 69 41 55 52 Carbon Nanotubes, Graphene, and Associated Devices VI, edited by Didier Pribat, Young Hee Lee, Manijeh Razeghi, Seunghyun Baik, Proc. of SPIE Vol. 8814, 88140I · © 2013 SPIE CCC code: 0277-786X/13/$18 · doi: 10.1117/12.2030011 Proc. of SPIE Vol. 8814 88140I-1 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 01/20/2014 Terms of Use: http://spiedl.org/terms