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    Effect of friction on oxidative graphite intercalation and high-quality graphene formation

    Year: 2018

    Journal: Nat. Commun., Volume 9, FEB 26

    Authors: Seiler, Steffen; Halbig, Christian E.; Grote, Fabian; Rietsch, Philipp; Boerrnert, Felix; Kaiser, Ute; Meyer, Bernd; Eigler, Siegfried

    Organizations: Deutsche Forschungsgemeinschaft (DFG) [SFB 953, EI938/3-1]; Graduate School Molecular Science (GSMS); Fonds der Chemischen Industrie (FCI)

    Oxidative wet-chemical delamination of graphene from graphite is expected to become a scalable production method. However, the formation process of the intermediate stage-1 graphite sulfate by sulfuric acid intercalation and its subsequent oxidation are poorly understood and lattice defect formation must be avoided. Here, we demonstrate film formation of micrometer-sized graphene flakes with lattice defects down to 0.02% and visualize the carbon lattice by transmission electron microscopy at atomic resolution. Interestingly, we find that only well-ordered, highly crystalline graphite delaminates into oxo-functionalized graphene, whereas other graphite grades do not form a proper stage-1 intercalate and revert back to graphite upon hydrolysis. Ab initio molecular dynamics simulations show that ideal stacking and electronic oxidation of the graphite layers significantly reduce the friction of the moving sulfuric acid molecules, thereby facilitating intercalation. Furthermore, the evaluation of the stability of oxo-species in graphite sulfate supports an oxidation mechanism that obviates intercalation of the oxidant.
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