ELECTROCHEMICAL-BEHAVIOR AND SURFACE-ANALYSIS OF CRUDE AND MODIFIED CARBON ELECTRODES FOR FLUORINE PRODUCTION

During the electrolytic preparation of elemental fluorine in molten KF-2HF using carbon anodes, the electronic transfer is usually inhibited by a passivating layer of graphite fluorides, CF(x), at the surface of the electrode. Significant improvements may be obtained if a conducting ternary carbon-aluminium-fluorine compound, ie a graphite intercalation compound denoted G.I.C., is formed at the interface instead of graphite fluorides. ''Modified'' carbon electrodes were prepared from crude carbon samples by impregnation technique. Their electrochemical behaviour was studied by cyclic voltammetry and impedance measurements. The chemical composition of the surface was determined by ex situ XPS. It is shown that the electronic transfer is enhanced, so as the wettability of the electrodes by the melt. Thus, the anodic overvoltage is significantly decreased.