Jiro Hiraiwa

A novel carbon electrode impregnated by molten metal fluoride for the production of fluorine

The catalytic ability of solid LiF or AlF3 to decrease anode overvoltage and the anode behavior of a carbon electrode impregnated with molten LiFNaF or AlF3−NaF in KH2F3 were investigated. When the graphite-sheet electrode was electrolyzed in a bath containing 2% by weight LiF or AlF3, the anode effect did not occur, but fluorine-graphite intercalation compounds were formed by catalytic reaction of these solid metal fluorides. Under these conditions, the dispersion term of the surface energy of the electrode was nearly the same as that of the control electrode, however the polar term of the electrode increased 30 times over that of the control electrode. The carbon electrode impregnated with molten LiF-NaF or AlF3-NaF was operated with a high current density (e.g. 20 A dm−2) for 40 days without the occurrence of the anode effect; contamination of CF4 in the F2 was as low as 2 ppm.

New carbon electrode impregnated with molten metal fluorides in fluorine cell

Abstract The anode behaviors of new carbon electrodes impregnated with several kinds of molten metal fluorides in fluorine cell are reported. The molten fluorides are belong to IA and IIA of main group elements or IIIA of transition elements of the periodic table. The obtained results are summarized as following; 1. The carbon electrode impregnated with molten LiF was the lowest anode overvoltage among all impregnated electrodes. 2. All impregnated electrodes were able to operate at high current density such as 20 to 25A/dm 2 and anode effect was not observed in the course of electrolysis. 3. The contamination of carbon tetrafluoride in fluorine was so low as 10 to 20 ppm compared with 500 to 1000 ppm in a conventional carbon electrode.