New insights into oxygen surface coverage and the resulting two-component structure of graphene oxide

Ignacio Martin-Gullon, Juana M. Pérez, Daniel Domene, Anibal J.A. Salgado-Casanova, Ljubisa R. Radovic

Research output: Contribution to journalArticle

Abstract

Elucidating the essential details of the structure of graphene oxide (GO) is still a challenge. There is no consensus in the increasingly abundant literature, especially relating to the epoxy groups as the main surface complexes in the basal plane, as well as the simultaneous presence of GO sheets and oxidative debris (OD), with a large difference in their oxygen content. In the present work we characterized the base-washed GO (bwGO) sheets, the OD and the humic fraction of the OD obtained by base digestion, when the parent GO was dispersed by applying sonication, a routine procedure when starting from dried graphite oxide. When sonication is not applied, the amount of OD detected is considerably lower, indicative of its formation before base digestion. The presence of lactols and carboxylic anhydrides as the dominant surface complexes at graphene edges is consistent with all the characterization results, as well as with the general knowledge of surface chemistry of carbon materials ranging from coal to graphite. These findings suggest that the Hummers-Offeman reaction produces a chemical scissor effect during the water/hydrogen peroxide quenching step, yielding a broad size distribution of GO sheets, with little in-plane oxidation and the vast majority of edges being oxidized to form oxepinone-type functionalities.

Original languageEnglish (US)
Pages (from-to)406-417
Number of pages12
JournalCarbon
Volume158
DOIs
Publication statusPublished - Mar 2020

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All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Materials Science(all)

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