Synthesis and Characterization of Highly Fluorinated Graphite Containing sp² and sp³ Carbon

Abstract

Highly fluorinated graphites were obtained by reaction of fluorine with graphite, at room temperature, in the presence of iodine pentafluoride and hydrogen fluoride. The refluorination between 100 and 600 °C yielded a series of fluorinated graphites with semiionic and covalent C-F bonds with varying amounts of sp 2 -and sp 3 -type carbon hybridization. Three types of materials have been generated: for re-fluorination lower than 400 °C, the C-F bond is still mainly semi-ionic and the carbon atoms are sp 2 coplanar; for re-fluorination temperatures between 400 and 550 °C, "hybrid" graphite fluorides characterized by two types of C-F bonds, semi-ionic and covalent, with sp 2 and sp 3 carbon hybridization were found. For higher re-fluorination temperatures (between 550 and 600 °C), despite a similar fluorination amount and a covalent C-F bond, the sp 2 character never completely vanished even at a high re-fluorination temperature of 600 °C. At such a temperature, a directly fluorinated graphite would be of the pure sp 3 type.

Synthesis and characterization of microporous carbons templated by ammonium-form zeolite Y

“…This peak was also observed on the XRD patterns of porous carbon templated by zeolite Y (H-form). It is believed that the presence of this XRD peak may be related to the HF treatment because a similar broad XRD peak at about 14°2h has also been seen on the graphite carbons after treatment by fluorination [38,39], and indexed in a hexagonal system either as the 0 0 1 reflection or as the 0 0 2 reflection, corresponding to an average interlayer spacing of about 0.631 nm [39]. Further investigation to attribute this peak is undergoing.…”

Reversible Intercalation of Fluoride-Anion Receptor Complexes in Graphite

“…Room temperature chemical fluorination of graphite in the presence of various fluorides such as HF, WF 6 , SbF 5 , and IF 5 has been demonstrated by others up to C 1.0 F 0.89 ͑I 0.02 H 0.06 ͒. 1 Under these preparation conditions, the sp 2 carbon hybridization is maintained, and the C-F bonding is ionic. Electrochemical fluorination of graphite in aqueous or anhydrous HF media is also possible, resulting in ionic or semi-covalent C x -F depending on the degree of fluorination, though this process is not significantly reversible and has poor Coulombic efficiency.…”

“…As cathodes in lithium batteries, carbon-fluoride ͑C-F͒ compounds offer very high theoretical specific capacity, on the scale of 1785 mAh/g for C 1.25 F, though to date, all C-F compounds regardless of preparation conditions are strictly non-rechargeable. A rechargeable C-F cathode would be very desirable in terms of specific energy relative to conventional lithium-ion transition metal oxide cathodes, though there are numerous difficulties associated with reversible fluorination of carbon which relate to a large extent to the nature of the C-F bond.…”

Insights on the reactivity of ordered porous carbons exposed to different fluorinating agents and conditions

“…The 13 C chemical shift of sp 2 carbon atoms is expected at around 120 ppm [22,[51][52][53][54], the interaction with neighboring C-F bonds resulting in a shift towards high values, up to 145 ppm for highly Table 1 -Textural properties of carbonaceous materials before and after different fluorination treatments. fluorinated room temperature graphite fluoride [55][56][57].…”