Dielectric relaxation characteristics of chemically reduced graphite oxide

Graphite oxide of various degrees of dehydration or chemically reduced with different concentrations of sodium borohydride have been synthesised. Samples were characterised with X-ray diffractometry and infrared spectroscopy, then studied using Raman, X-ray photoelectron (XPS), nuclear magnetic resonance (NMR) and impedance spectroscopies. The trend in their concentrations of epoxy, hydroxyl group and sp(2) carbon, as calculated from XPS and NMR data, agreed with their vacancies concentrations as deduced from Raman spectra. Analysis of observed complex impedance peaks points to three different relaxation processes. One, obviously, is the rotation of intercalated water. The other two involve dipoles originating from polar hydroxyl groups. Loss peaks seen in less reduced graphite oxide have an activation energy of 0.16 eV, and are ascribed to the breaking of a hydrogen bond (-O-H center dot center dot center dot O<) between a hydroxyl attached to a carbon grid and an epoxy group on the adjacent carbon grid. The other, displayed in more reduced samples and of 0.08 eV in activation energy, derive from hydrogen bonds (-O-H-center dot center dot center dot pi) between hydroxyls and pi electrons on adjacent carbon grids. (C) 2015 Elsevier Ltd. All rights reserved.