Direct conversion mechanism of fluorine–GIC into poly(carbon monofluoride), (CF)n Original Research Article

The reaction mechanisms of a stage-1 fluorine–graphite intercalation compound (GIC), C2.5F, with 0.10 MPa of fluorine gas have been studied at 573–773 K. The original stage-1 structure of C2.5F with semi-ionic C–F bonds and planar sp2 carbon sheets is maintained in most part of the compound after the reaction at 573 K, although a large number of covalent C–F bonds are formed on the surface. This compound is partially or completely converted to poly(carbon monofluoride), (CF)n, with covalent C–F bonds and puckered sp3 carbon sheets at 673 or 773 K, respectively. Single-phase (CF)n obtained at 773 K possesses remarkably small BET specific surface area, 61 m2/g carbon, almost unchanged from the value of the precursor C2.5F (69 m2/g carbon). In this reaction, the accommodation of fluorine atoms supplied from the atmosphere into the galleries of C2.5F is facilitated by the rearrangement of originally intercalated fluorine atoms in the GIC, forming (CF)n with fewer defects compared to those by the conventional direct fluorination of graphite.