The anodic behaviors of nickel and carbon electrodes in molten fluorides containing HF are described in view of studies on analysis of the oxidized layer formed on the electrode surface, NF3 formation and the anodic dissolution of nickel electrode. The current efficiency for NF3 formation depends on the anode material, the structural material of the cell and the composition of electrolyte. Also, the consumption of nickel anode depends on the structural material of the cell and the composition of electrolyte. The existence of nickel oxide in the oxidized layer on the nickel anode retards the consumption of nickel anode and increases the electric conductivity of the oxidized layer. Graphite-fluorine intercalation compounds and trivalent and/or tetravalent nickel compounds are detected on carbon and nickel, respectively, by the electrochemical method, X-ray photoelectron spectroscopy (XPS), and X-ray diffractometry (XRD). The rate of NF3 formation in a well dehydrated melt of NH4F·2HF is mainly affected by the oxidation ability of the compounds formed on the anode. The addition of LiF increases the current efficiency for NF3 formation, presumably because of deposition of Li2NiF6 on the nickel anode.
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