Towards full repair of defects in reduced graphene oxide films by two-step graphitization
The complete restoration of a perfect carbon lattice has been a central issue in the research on graphene derived from graphite oxide since this preparation route was first proposed several years ago, but such a goal has so far remained elusive. Here, we demonstrate that the highly defective structure of reduced graphene oxide sheets assembled into free-standing, paper-like films can be fully repaired by means of high temperature annealing (graphitization). Characterization of the films by X-ray photoelectron and Raman spectroscopy, X-ray diffraction and scanning tunneling microscopy indicated that the main stages in the transformation of the films were (i) complete removal of oxygen functional groups and generation of atomic vacancies (up to 1,500 °C), and (ii) vacancy annihilation and coalescence of adjacent overlapping sheets to yield continuous polycrystalline layers (1,800–2,700 °C) similar to those of highly oriented graphites. The prevailing type of defect in the polycrystalline layers were the grain boundaries separating neighboring domains, which were typically a few hundred nanometers in lateral size, exhibited long-range graphitic order and were virtually free of even atomic-sized defects. The electrical conductivity of the annealed films was as high as 577,000 S·m−1, which is by far the largest value reported to date for any material derived from graphene oxide, and strategies for further improvement without the need to resort to higher annealing temperatures are suggested. Overall, this work opens the prospect of truly achieving a complete restoration of the carbon lattice in graphene oxide materials.
Keywordsgraphene graphene oxide films annealing defect
Unable to display preview. Download preview PDF.
- Mattevi, C.; Eda, G.; Agnoli, S.; Miller, S.; Mkhoyan, K. A.; Celik, O.; Mastrogiovanni, D.; Granozzi, G.; Garfunkel, E.; Chhowalla, M. Evolution of electrical, chemical, and structural properties of transparent and conducting chemically derived graphene thin films. Adv. Funct. Mater. 2009, 19, 2577–2583.CrossRefGoogle Scholar
- Yang, D. X.; Velamakanni, A.; Bozoklu, G.; Park, S.; Stoller, M.; Piner, R. D.; Stankovich, S.; Jung, I.; Field, D. A.; Ventrice Jr, C. A. et al. Chemical analysis of graphene oxide films after heat and chemical treatments by X-ray photoelectron and micro-Raman spectroscopy. Carbon 2009, 47, 145–152.CrossRefGoogle Scholar
- Solís-Fernández, P.; Rozada, R.; Paredes, J. I.; Villar-Rodil, S.; Fernández-Merino, M. J.; Guardia, L.; Martínez-Alonso, A.; Tascón, J. M. D. Chemical and microscopic analysis of graphene prepared by different reduction degrees of graphene oxide. J. Alloy. Compd. 2012, 536, S532–S537.CrossRefGoogle Scholar
- Cançado, L. G.; Takai, K.; Enoki, T.; Endo, M.; Kim, Y. A.; Mizusaki, H.; Jorio, A.; Coelho, L. N.; Magalhães-Paniago, R.; Pimenta, M. A. General equation for the determination of the crystallite size L a of nanographite by Raman spectroscopy. Appl. Phys. Lett. 2006, 88, 163106.CrossRefGoogle Scholar
- Spain, I. L. Electronic transport properties of graphite, carbons, and related materials. In Chemistry and Physics of Carbon. Vol. 16. Walker Jr., P. L.; Thrower, P. A., Eds.; New York: Marcel Dekker, 1981; pp 119–304.Google Scholar
- Magonov, S. N.; Whangbo, M. H. Surface Analysis with STM and AFM: Experimental and Theoretical Aspects of Image Analysis; VCH: Weinheim, 1996.Google Scholar