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 o f the electrode. Significant improvements may be obtained if a conduct ing ternary carbon-aluminium-fluorine compound, ie a graphite intercal ation compound denoted G.I.C., is formed at the interface instead of g raphite fluorides. ''Modified'' carbon electrodes were prepared from c rude carbon samples by impregnation technique. Their electrochemical b ehaviour 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 wett ability of the electrodes by the melt. Thus, the anodic overvoltage is significantly decreased.