Preparation and Characterization of Graphite Fluorometallate Salts and Graphite Fluorides by Chemical and Electrochemical Methods.

摘要

Graphite intercalation compounds of main-group metal fluorides are prepared utilizing Cl 2 as an oxidizing agent. The action of Cl 2 with GeF 4 and Cl 2 /HF with either PF 5 or BF 3 on graphite produces fluorometallate salts. The relationship between the calculated enthalpy change for the reduction half-reaction and degree of intercalation is discussed. The electrochemical oxidation of graphite in 49% aqueous HF generates, at the oxidation limit, a 2nd stage graphite fluoride with a charge on carbon of C(sub 10 to the -14)(sup -1). The fully-oxidized product is a 2nd stage analog of the planar-sheet graphite fluorides produced by the chemical or electrochemical fluorination of graphite in liquid anhydrous hydrogen fluoride (AHF). The fluorometallate salts prepared by electrochemical oxidation of graphite in an AHF/alkali metal fluorometallate salt (M = As, P, B, Sn) electrolyte are examined. The chemical fluorination of 2nd- and 3rd-stage C(sub x)AsF sub 6 salts with AHF/F(sub 2) at ambient temperature produces a planar-sheet graphite fluoride phase with a C/F ratio as low as 1.3 along with a C(sub x)AsF(sub 6) phase. The reaction of graphite with AHF/SnF(sub 4) F(sub 2) results in the rapid disappearance of SnF sub 4 , F sub 2 uptake, and color change of the solid from grey to blue-black. Graphite reacts with AHF/K sub 2 MnF sub 6 in a stoichiometric ratio of at least 1 Mn for 6 C to produce MnF sub 3 and a C(sub x)F phase. The reaction of excess PF sub 5 with a well-evacuated C(sub x)BF sub 4 (center dot) deltaBF sub 3 salt yields partial displacement of BF sub 3 . When PF(sub 5) + HF are employed, no BF sub 3 is displaced from the fluoroborate salt. 21 refs., 15 figs., 18 tabs. (ERA citation 13:057104)