POLISHED CARBON ELECTRODES FOR IMPROVING THE FLUORINE PRODUCTION PROCESS

Improvements in the fluorine production process may be obtained by forming a ternary conducting layer CFxMy at the surface of the carbon anodes (M is a metal: Li, Mg, Al,...). Electron transfer at the interface is thus enhanced and the wettability of the electrode by the KF-2HF melt is improved. In this paper, we show that polishing the carbon electrodes with alumina or magnesia actually dopes the carbon by mechanical insertion of the latter compound. Scanning electron microscopy experiments show that particles of aluminium oxide or magnesium oxide are inserted during the polishing process; they give the corresponding fluorides during electrolysis in the KF-2HF melt. A surfacic ternary conducting compound is formed, as in the case of electrodes doped by additions of LiF or AlF3 into the melt. The electrochemical behavior of the polished electrodes has been studied by cyclic voltammetry experiments and impedance measurements. © 1990 Chapman and Hall Ltd.