Graphite fluoride electrodes

In equation 5, C is amorphous carbon and CF2 changes to many perfluorocarbons, such as CF4, C2F6, etc., by secondary reactions. The surface coverage of graphite fluoride on the anode depends on the relative reaction rates of equations 4 and 5. Equation 6 has been introduced to analyze the wettability of the carbon surface with graphite fluoride formed on it.2 It shows the relationship between the fraction of effective surface for equation 3 per unit surface area of carbon (a) and the contact angle (0) of a fluorine gas bubble on the surface of the carbon electrode.2... 

Graphite reacts with alkali metals, for example potassium, to form compounds which are non-stoichiometric but which all have limiting compositions (for example K C) in these, the alkaU metal atoms are intercalated between the layers of carbon atoms. In the preparation of fluorine by electrolysis of a molten fluoride with graphite electrodes the solid compound (CF) polycarbon fluoride is formed, with fluorine on each carbon atom, causing puckering of the rings. 

A further advantageous modification of electrodes is claimed by Watanabe [154] for the Central Glass Co. Ltd. which uses anodes coated with a composite layer of nickel containing a dispersed eutectoid of PTFE particles or fluorinated graphite particles. The low surface energy nickel based composite is said to improve the yield of perfluorooctanesulphonyl fluoride to 40.5 % in ECF. 

At an applied potential of 2.2-3.6 V to a graphite electrode in melts of alkali metal fluorides or beryllium fluoride at 500-700 "C, formation of CF, C Fg and COF was noted [2249]. The formation of COFj has been noted similarly during the electrolysis of oxofluorotitanate melts using graphite anodes [67]. 

A schematic representation of the conductivity cell assembly is shown in Figure 8.10. The graphite crucible, which was used as the molten salt holder, was of a 3-cm inner diameter and was also used as the counter electrode connected to a LCR Impedance Meter through a thermocouple Inconel protection sheath. In the upper part of the graphite crucible, a BN holder of 3.8 cm inner diameter was placed, in which the pyrolytic BN tube-type conductivity cell was vertically fastened. The tube cell, made of vapor-deposited pyrolytic BN, was dense, non-conductive, with a consistent inner diameter, and able to resist corrosion attack of molten fluoride. The pyrolytic BN tube was immersed in... 

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