Effects of Charging and Perpendicular Electric Field on Graphene Oxide
We present a first-principles study of the effects of charging, electric field on the oxidation/deoxidation of graphene oxide consisting of epoxy and hydroxly groups. We first determined the proper basis set which prevents the spurious spilling of electro
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Effects of Charging and Perpendicular Electric Field on Graphene Oxide H. Hakan Gürel, M. Topsakal and S. Ciraci
Abstract We present a first-principles study of the effects of charging, electric field on the oxidation/deoxidation of graphene oxide consisting of epoxy and hydroxly groups. We first determined the proper basis set which prevents the spurious spilling of electrons of graphene oxide, when negatively charged or exerted by perpendicular electric field and treated with periodic boundary conditions. Applied perpendicular electric field to graphene surface is provided side specific functionalization. We showed that the bonds between oxygen and graphene are weakened under applied electric field. For specific values of excess charge or perpendicular electric field, oxygen atom moves to the top site from bridge site which is normally absorbed in equilibrium. Individually adsorbed oxygen atoms cannot form oxygen molecules due to an energy barrier. This energy barrier is dramatically weakened, when negatively charged or exerted by an electric field. Beside the epoxy groups, hydroxyl groups have an important role of oxidation/deoxidation of graphene oxide. Charging and perpendicular electric field mediates the reduction of graphene oxide through the formation of H2O and H2O2. Our results explain the role of external effects to the reduction of graphene oxide.
H. Hakan Gürel Technology Faculty, Information Systems Engineering Department, Kocaeli University, 41380 Kocaeli, Turkey e-mail: [email protected] M. Topsakal UNAM-National Nanotechnology Research Center, Bilkent University, 06800 Ankara, Turkey e-mail: [email protected] S. Ciraci (&) Department of Physics, Bilkent University, 06800 Ankara, Turkey e-mail: [email protected] © Springer International Publishing Switzerland 2016 H. Ünlü et al. (eds.), Low-Dimensional and Nanostructured Materials and Devices, NanoScience and Technology, DOI 10.1007/978-3-319-25340-4_11
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Introduction
Graphene oxide (GOX) has been an important material because it allows the production of large scale graphene sheets through the reduction of oxidized multilayer graphene [1, 2]. Despite the great amount of experimental and theoretical research carried out recently, [1–16] a thorough understanding of the interaction of epoxy and hydroxyl groups with graphene resulting in oxidation/deoxidation process are not fully understood yet. Active research to date has concluded that the oxidation and reduction of graphene are, in fact, rather complex and comprise the interplay of various molecules and atoms, such as O, O2, CO2, OH, H, H2O, as well as external agents. GOX has been also a subject of interest because the electronic properties of graphene, in particular its linear p and p bands, [17] which cross at the Fermi level undergo dramatic changes upon oxidation [18–21]. Introducing a band gap, which varies with oxygen coverage and hence changes semimetallic graphene into a semiconductor, has been an active field of study in graphene based
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