Graphite fluorides: An XPS study of a new type of C-F bonding

Highly oriented pyrolytic graphite was fluorinated at room temperature with molecular fluorine at 2.5 atm for 8 days to 2 months without addition of any catalyst. Under these mild conditions we obtained graphite-fluorine intercalation compounds in a wide range of stoichiometry 64 ⩾ C/F ⩾ 4. Except for the highest fluorine content (C/F ⩽ 4) all our samples are better conductors than graphite. A thorough XPS study of clean cleaved internal surfaces of the oriented samples shows a new kind of carbon-fluorine bonding. The binding energies of the C1s and F1s photoemission peaks are 287.3 ± 0.2 and 685.7 ± 0.2 eV. These values differ from those of typical covalent bonds (290.4 and 689.6 eV) and the nature of the bond is probably different from that of covalent C-F.