Raman, Infrared and n.m.r. Studies of the Graphite Hydrofluorides CxF1- δ(HF)δ (2 <= x <= 5)

Raman spectra of C_xF_1-δ(HF)_δ (x/δ ≈ 12) show bands at 1600, 1355 and 839 cm^-1, which are attributed to graphite-like vibrational modes of the carbon atom sheets. The infrared spectra show, in addition to graphite-like bands, absorptions at 1270 and 1100 cm^-1, which are attributed to C--F stretching. Variable contact-time cross-polarized magic-angle spinning ¹³C nuclear magnetic resonance spectra (c.p.m.a.s. ¹³C n.m.r.) have been obtained for x = 2.05 and 3.70. In both spectra, two peaks (+ 135/10⁶ and + 88/10⁶ chemical shift from TMS) are seen, which are attributed, respectively, to graphitic and C--F carbons. The ratio of graphitic to C--F carbon atoms has been found to be 1.6(2): 1 in C_2.05F_0.82(HF)_0.18. The carbon atom sheets in C_xF_1-δ(HF)_δ appear to be very similar to those in pristine graphite. The bonding of fluorine to carbon is highly ionic. Bonding models are discussed.