C 2022, 8, 27. https://doi.org/10.3390/c8020027 www.mdpi.com/journal/carbon Article Chemical Production of Graphene Oxide with High Surface Energy for Supercapacitor Applications Mehdi Karbak 1,2 , Ouassim Boujibar 1, *, Sanaa Lahmar 1 , Cecile Autret-Lambert 3 , Tarik Chafik 2 and Fouad Ghamouss 1,4 1 Laboratory of Physical-Chemistry of Materials and Electrolytes for Energy (PCM2E), University of Tours, 37200 Tours, France; mehdi7karbak@gmail.com (M.K.); sanaa.lahmar@etu.univ-tours.fr (S.L.); fouad.ghamouss@um6p.ma (F.G.) 2 Laboratory of Chemical Engineering and Resources Valorization (LGCVR), Faculty of Sciences and Techniques, University Abdelmalek Essaadi, B.P. 416, Tangier 90010, Morocco; tchafik@uae.ac.ma 3 Materials Research Group, Microelectronics, Acoustics and Nanotechnologies, GREMAN, (UMR 7347), University of Tours, 37200 Tours, France; autret@univ-tours.fr 4 Department of Materials Science, Energy, and Nano-Engineering, Mohamed VI Polytechnic University, Ben Guerir 43150, Morocco * Correspondence: ouassim.boujibar@univ-tours.fr or boujibar.ouassim@gmail.com; Tel.: +33-7-64-77-23-88 Abstract: The chemical exfoliation of graphite to produce graphene and its oxide is undoubtedly an economical method for scalable production. Carbon researchers have dedicated significant re- sources to developing new exfoliation methods leads to graphene oxides with high quality. How- ever, only a few studies have been dedicated to the effect of the starting graphite material on the resulting GO. Herein, we have prepared two different GOs through chemical exfoliation of graphite materials having different textural and structural characteristics. All samples have been subjected to structural investigations and comprehensive characterizations using Raman, X-ray diffraction, scanning electron microscopy, TGA, N2 physisorption, and FTIR spectroscopy. Our results provide direct evidence of how the crystallite size of the raw graphite affects the oxidation degree, surface functionality, and sheet size of the resulting GO. Building on these significant understandings, the optimized GO achieves a highly specific capacitance of 191 F.g −1 at the specific current of 0.25 A.g −1 in an aqueous electrolyte. This superior electrochemical performance was attributed to several fac- tors, among which the specific surface area was accessible to the electrolyte ions and oxygenated functional groups on the surface, which can significantly modify the electronic structure of gra- phene and further enhance the surface energy. Keywords: graphene oxide; graphene; graphite; supercapacitor 1. Introduction Today, many ongoing studies are focusing on every possible type of advanced en- ergy storage device, including alkali metal-ion batteries, fuel cells, and supercapacitors [1–3]. The latter are considered among the most promising devices due to related high power densities and a long cyclic life [4]. Generally, electrodes with a large surface area and a well-designed pore size distribution are found to be responsible for the excellent capacitive performance of supercapacitors [5]. A remarkable number of different types of carbon materials, such as activated carbon, graphene, carbon nanotubes, and carbon nan- ofibers, have been investigated to check their performances as electrodes for supercapac- itor applications [6–8]. Among them, two-dimensional graphene-like sheets have recently received rapidly growing attention in supercapacitors, mainly because of their highly spe- cific surface area (∼2600 m 2 .g −1 ), superior electrical conductivity, and excellent chemical Citation: Karbak, M.; Boujibar, O.; Lahmar, S.; Autret-Lambert, C.; Chafik, T.; Ghamouss, F.; Chemical Production of Graphene Oxide with High Surface Energy for Supercapacitor Applications. C 2022, 8, 27. https://doi.org/10.3390/ c8020027 Academic Editors: Giuseppe Cirillo and Peter Harris Received: 2 March 2022 Accepted: 5 May 2022 Published: 7 May 2022 Publisher’s Note: MDPI stays neu- tral with regard to jurisdictional claims in published maps and institu- tional affiliations. Copyright: © 2022 by the authors. Li- censee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and con- ditions of the Creative Commons At- tribution (CC BY) license (https://cre- ativecommons.org/licenses/by/4.0/).