Electron oxidation of graphite by fluorospecies

Technical Report · Sat Sep 01 04:00:00 EDT 1984

DOI:https://doi.org/10.2172/6230443· OSTI ID:6230443

Rosenthal, G L

The fluoride-ion affinity (A/sub F/sup -//) of phosphorus pentafluoride was determined to be 100 kcal/mole from the heats of reaction of the Lewis bases SF/sub 4/ and ClO/sub 2/F with PF/sub 5/ near room temperature. The fluoride-ion affinity of boron trifluoride was determined to be 92 kcal/mole from the heat of reaction of ClO/sub 2/F with BF/sub 3/. The crystal structure of ClO/sub 2/BF/sub 4/ was determined and a precise lattice energy was calculated from this structure and used to determined A/sub F/sup -//. Both PF/sub 5/ and BF/sub 3/ were found to react with graphite in the presence of fluorine gas to yield a variety of non-stoichiometric compounds. The fluoride-ion affinity of silicon tetrafluoride is not known, but it does not react with graphite and F/sub 2/ except at high pressures. These and previous results suggested a threshold in oxidizing power of intercalating species below which the oxidative intercalation reaction would not occur. The reduction of C/sub x/PF/sub 6/ by PF/sub 3/ proved that the reaction is thermodynamically controlled to some extent. The displacement of PF/sub 5/ in C/sub x/PF/sub 6/ by BF/sub 3/ (with a smaller A/sub F/sup -//) suggested that two BF/sub 3/ molecules may have a larger fluoride-ion affinity than one PF/sub 5/ and that B/sub 2/F/sub 7//sup -/ may be a stable anion in graphite. Conductivity studies of PF/sub x/ and BF/sub y/ salts showed that a large drop in conductivity when the reaction reaches first stage is due in the most part to direct fluorination of carbon in graphite.

• Research Organization: Lawrence Berkeley Lab., CA (USA)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 6230443
• Report Number(s): LBL-18367; ON: DE85001196
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
BORON COMPOUNDS
CARBON
CHEMICAL REACTIONS
CLATHRATES
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELEMENTAL MINERALS
ELEMENTS
FLUORIDES
FLUORINE COMPOUNDS
FLUOROBORATES
GRAPHITE
HALIDES
HALOGEN COMPOUNDS
MINERALS
NONMETALS
OXIDATION
PHOSPHORUS COMPOUNDS
PHOSPHORUS FLUORIDES
PHYSICAL PROPERTIES