Structural insights into hydrogenated graphite prepared from fluorinated graphite through Birch−type reduction

Abstract

Hydrogenated graphite was synthesized through a Birch-type reduction by treating fluorinated graphite ((CFx)(n), x similar to 1.1) with a solution of Li in liquid NH3 followed by the addition of H2O 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 C1H0.60O0.06N0.01 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 degrees 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.