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A study of polybromide chain formation using carbon nanomaterials via density functional theory approach

Lookup NU author(s): Professor Patrick Briddon

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).

Abstract

© 2016 The Author(s). This open access article is distributed under a Creative Commons Attribution (CC-BY) 4.0 license. We use a density functional theory approach under the local density approximation (DFT/LDA) to describe the formation of polybromide chain structures, their stretching frequency modes and charge transfer induced by the interaction of these molecules with a graphene sheet. In many cases, we find polybromides to be more thermodynamically stable than the equivalent Br2 molecular structures adsorbed on graphene sheet. This results in lower frequency stretch modes at around 170–190 cm−1. We propose that these are rarely observed experimentally due to the bromination techniques used, which introduces molecular Br2 into the carbon host material. Charge transfer with their host material means that these molecules and their associated hole charge in the neighbouring carbon materials, are then coulombically repelled from other bromine molecules which acts as a barrier to combination into polybromides. Our calculated barrier for polybromide formation (2Br2→Br4) on a graphene sheet was 0.35 eV which is an exothermic process with an enthalpy value of −0.28 eV. Therefore, thermodynamically, chain polybromide formation seems to be favourable but kinetically, is unlikely, since there is an activation barrier that needs to be overcome to give stable bromine chain structures.

Publication metadata

Author(s): Yaya A, Ewels CP, Efavi JK, Agyei-Tuffour B, Kan-Dapaah K, Onwona-Agyeman B, Abavare EKK, Hassanali A, Briddon PR

Publication type: Article

Publication status: Published

Journal: Cogent Engineering

Year: 2016

Volume: 3

Issue: 1

Online publication date: 17/11/2016

Acceptance date: 10/11/2016

Date deposited: 06/04/2017

ISSN (electronic): 2331-1916

Publisher: Cogent OA

URL: https://doi.org/10.1080/23311916.2016.1261509

DOI: 10.1080/23311916.2016.1261509

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