Functional surfaces of carbon materials

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Radiation-chemical reduction of graphen oxide

The discovery of graphene is one of the most important events in the chemistry and physics of carbon materials within the last decade. In 2020 more than 50 % of the global market for graphene-based products is expected to be covered by reduced graphene oxide (RedGO) used in the supercapacitors. The most effective route to obtain low cost, good quality graphene in form of highly reduced GO is by means of the reduction of graphene oxide (GO) in its colloidal suspensions.

Drawbacks of commenly used methods include high toxicity and explosivity (hydrazine); too expensive (vitamin C or HI), too long treatment time (40 h for gamma-radiolysis), high reaction temperatures (> 90 ºC), waste management and difficult up-scaling etc. By EB irradiation of aqueous GO solutions highly reducing species like eaq– and H• are produced; additionally strong oxidant •OH radicals can be converted into reducing radicals derived from alcohols with reduction potentials in a wide range (0 to -2.0 V).

Benefits:

  • realizable at RT within minutes giving highly quality RedGO (30000 S/m)
  • the process is eco-friendly and easily up-scalable
  • in contrast to gamma-radiolysis, fast reduction can be achieved even under air
  • further modification of RedGO with free-radicals (functionalisation) is possible

 

Formation of graphene by electron-irradiation with a 10 MeV electron accelerator. The XPS-C1s-spectra confirm the decrease of C-O bonds (light green, red, blue) in graphene oxide (a) upon reduction to graphene (b).
TEM images of (a) GO and (c) RedGO. SAED patterns of (b) GO and (d) RedGO.

Selected Publications

  • A. Kahnt, R. Flyunt, S. Naumov, W. Knolle, S. Eigler, R. Hermann, B. Abel
    Shedding light on the soft and efficient free radical induced reduction of graphene oxide: hidden mechanisms and energetics
    RSC Advances 6 (2016) 68835-68845
    DOI:10.1039/c6ra13085b

  • A. Kahnt, R. Flyunt, C. Laube, W. Knolle, S. Eigler, R. Hermann, S. Naumov, B. Abel
    How fast is the reaction of hydrated electrons with graphene oxide in aqueous dispersions?
    Nanoscale 7 (2015) 19432-19437
    DOI:10.1039/c5nr03444b

  • R. Flyunt, W. Knolle, A. Kahnt, A. Prager, A. Lotnyk, J. Malig, D. Guldi, B. Abel
    Mechanistic Aspects of the Radiation-Chemical Reduction of Graphene Oxide to Graphene-Like Materials
    Int. J. Radiat Biol. 90 (2014) 486-494
    https://doi.org/10.3109/09553002.2014.907934

  • R. Flyunt, W. Knolle, B. Abel, B. Rauschenbach
    Verfahren zur Herstellung von reduziertem Graphenoxid sowie damit hergestelltes reduziertes Graphenoxid und dessen Verwendung
    Patent DE 10 2012 024 329.4