An Improved Technique for the Exfoliation of Graphene Nanosheets and Utilization of Their Nanocomposites as Fuel Cell Electrodes Yuda Yürüm 1,a , Burcu Saner Okan 2 , Firuze Okyay 1 , Alp Yürüm 2 , Fatma Dinç 1 , Neylan Görgülü 1 , Selmiye Alkan Gürsel 1 1 Faculty of Engineering and Natural Sciences, Sabanci University, Orhanli, Tuzla, Istanbul 34956, Turkey 2 Nanotechnology Research and Application Center, Sabanci University, Orhanli, Tuzla, Istanbul 34956, Turkey a yyurum@sabanciuniv.edu Keywords: Graphene; Graphene nanosheets (GNS); Graphite oxide (GO). Graphene is a flat monolayer of carbon atoms tightly packed into a two-dimensional 2D honeycomb lattice. The graphene sheets in graphite interact with each other through van der Waals forces to form layered structure. The first graphene sheets were obtained by extracting monolayer sheets from the three-dimensional graphite using a technique called micromechanical cleavage in 2004 [1]. There are numerous attempts in the literature to produce monolayer graphene sheets by the treatment of graphite. The first work was conducted by Brodie in 1859 and GO was prepared by repeated treatment of Ceylon graphite with an oxidation mixture consisting of potassium chlorate and fuming nitric acid [2]. Then, in 1898, Staudenmaier produced graphite oxide (GO) by the oxidation of graphite in concentrated sulfuric acid and nitric acid with potassium chlorate [3]. However, this method was time consuming and hazardous. Hummers and Offeman found a rapid and safer method for the preparation of GO and in this method graphite was oxidized in water free mixture of sulfuric acid, sodium nitrate and potassium permanganate [4]. In the present work, graphene nanosheets (GNS) were separated from graphite by an improved, safer and mild method including the steps of oxidation, thermal expansion, ultrasonic treatment and chemical reduction. Graphene nanosheets (GNS) were exfoliated by following two ways. 1 st way, the longest exfoliation technique, contained these steps: graphite oxidation, ultrasonic treatment, thermal exfoliation, ultrasonic treatment and chemical reduction. 2 nd way, the shortest exfoliation technique, included graphite oxidation, ultrasonic treatment and chemical reduction. Both the reaction procedures with thermal expansion and without thermal expansion led to the formation of GNS. Fig. 1 showed SEM images of GNS obtained after thermal expansion and reduction process (1 st method), and by direct reduction process (2 nd method). With this improved method, the layers in the graphite material were exfoliated, and high-quality graphene nanosheets were produced with higher yields [5]. The mild procedure applied was capable of reducing the average number of graphene sheets from an average value of 86 in the raw graphite to 9 in GNS. As the oxidation time was increased from 50 min to 10 days, stacking height of graphene sheets decreased and thus the number of graphene layers decreased [6]. The variations in interplanar spacings, layer number, and percent crystallinity as a function of oxidation time indicated how stepwise chemical procedure influenced the morphology of graphite. All samples were investigated by SEM, XRD, TGA, AFM, HR-TEM, Raman Spectroscopy and surface area analyzer. Key Engineering Materials Vol. 543 (2013) pp 9-12 © (2013) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/KEM.543.9 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 193.255.135.254-17/01/13,10:07:06)