Structural insights into hydrogenated graphite prepared from fluorinated graphite through Birch−type reduction
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Carbon, ISSN: 0008-6223, Vol: 121, Page: 309-321
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Hydrogenated graphite was synthesized through a Birch−type reduction by treating fluorinated graphite ((CF x ) n, x ∼ 1.1) with a solution of Li in liquid NH 3 followed by the addition of H 2 O as the proton donor. The conversion was evaluated by Fourier transform infrared spectroscopy, Raman spectroscopy and powder X−ray diffraction. X−ray photoelectron spectroscopy and combustion elemental analysis were used to determine and quantify the chemical composition, giving an empirical formula of C 1 H 0.60 O 0.0 6 N 0.01 for the product with no more than 2 at.% of fluorine atoms remaining. Thermal dehydrogenation of the hydrogenated material – as investigated by thermogravimetric analysis coupled to mass spectrometry – predominately occurs over the range of 350–600 °C. The product was also analyzed using scanning electron microscopy, atomic force microscopy and transmission electron microscopy, which collectively supported the formation of hydrogenated graphene sheets through a wet−chemical route. To elucidate the structure of the hydrogenated sample, the material was investigated by solid−state nuclear magnetic resonance spectroscopy. Direct pulse and cross−polarization nuclear magnetic resonance measurements, including spin counting, spectral editing and 2D heteronuclear correlation experiments, revealed the nature of the sp 3 − and sp 2 −hybridized carbon nuclei, and indicated that methine, methylene and quaternary sp 3 −carbon atoms were present in the hydrogenated material.