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Open AccessArticle

Tailorable Synthesis of Highly Oxidized Graphene Oxides via an Environmentally-Friendly Electrochemical Process

1
Department of Analytical Chemistry, Physical Chemistry and Chemical Engineering, Faculty of Sciences, University of Alcalá, Alcalá de Henares, 28805 Madrid, Spain
2
Institute of Chemistry Research, “Andrés M. del Río” (IQAR), University of Alcalá, Ctra. Madrid- Barcelona Km. 33.6, Alcalá de Henares, 28805 Madrid, Spain
3
Department of Materials and National Graphene Institute, University of Manchester, Oxford Road, Manchester M13 9PL, UK
*
Author to whom correspondence should be addressed.
Nanomaterials 2020, 10(2), 239; https://doi.org/10.3390/nano10020239 (registering DOI)
Received: 29 November 2019 / Revised: 19 January 2020 / Accepted: 27 January 2020 / Published: 29 January 2020
(This article belongs to the Special Issue Properties and Applications of Graphene and Its Derivatives)
Graphene oxide (GO) is an attractive alternative to graphene for many applications due to its captivating optical, chemical, and electrical characteristics. In this work, GO powders with a different amount of surface groups were synthesized from graphite via an electrochemical two-stage process. Many synthesis conditions were tried to maximize the oxidation level, and comprehensive characterization of the resulting samples was carried out via elemental analysis, microscopies (TEM, SEM, AFM), X-ray diffraction, FT-IR and Raman spectroscopies as well as electrical resistance measurements. SEM and TEM images corroborate that the electrochemical process used herein preserves the integrity of the graphene flakes, enabling to obtain large, uniform and well exfoliated GO sheets. The GOs display a wide range of C/O ratios, determined by the voltage and time of each stage as well as the electrolyte concentration, and an unprecedented minimum C/O value was obtained for the optimal conditions. FT-IR evidences strong intermolecular interactions between neighbouring oxygenated groups. The intensity ratio of D/G bands in the Raman spectra is high for samples prepared using concentrated H2SO4 as an electrolyte, indicative of many defects. Furthermore, these GOs exhibit smaller interlayer spacing than that expected according to their oxygen content, which suggests predominant oxidation on the flake edges. Results point out that the electrical resistance is conditioned mostly by the interlayer distance and not simply by the C/O ratio. The tuning of the oxidation level is useful for the design of GOs with tailorable structural, electrical, optical, mechanical, and thermal properties. View Full-Text
Keywords: graphene oxide; electrochemical synthesis; oxidation level; exfoliation degree; morphology; interlayer spacing; surface defects; electrical resistance graphene oxide; electrochemical synthesis; oxidation level; exfoliation degree; morphology; interlayer spacing; surface defects; electrical resistance
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Díez-Pascual, A.M.; Sainz-Urruela, C.; Vallés, C.; Vera-López, S.; San Andrés, M.P. Tailorable Synthesis of Highly Oxidized Graphene Oxides via an Environmentally-Friendly Electrochemical Process. Nanomaterials 2020, 10, 239.

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