Electrochemical fluorination of metals by using a fluoride ion conductor

A new electrochemical method for fluorination of metals by using a fluoride ion conductor, PbSnF4 was proposed and it was applied for the fluorination of tungsten, vanadium and molybdenum. When these metals were fluorinated by the potential sweep method, the current–potential curve varied drastically, depending on the potential sweep rates. When the sweep rates were low, one or two current peaks were observed and then the metal electrodes were passivated probably because the thin film consisting of insulating and involatile metal fluorides completely covered the electrode surface. When the sweep rate was high enough, a large current passed through the cell and volatile product was formed. In the case of the fluorination of tungsten, the color of the product and the EPMA image of the hydrolyzed products deposited on Pt lead and reference electrodes suggested the formation tungsten hexafluoride. The formation of volatile product enabled the succesive electrochemical fluorination of metals without passivating the electrode surface.