Electrochemical behavior of molten fluoride-water system

The cathodic behavior of a molten Fluoride-water system was investigated by the potential sweep method. LiF-KF-NaF eutectic melt was used as an electrolyte and HF-H2O gas mixture with Ar as a carrier was bubbled into it. Gold wire was used as a working electrode. The peak currents dueto the reduction of HF and H2O were clearly observed. The relations between peak currents and the square roots of the scanning rates were linear, strongly suggesting that the reduction reactions of the HF and H2O dissolved in the melt were diffusion controlled. From the linearity of the relations between peak currents and partial pressures of HF and H2O in the low partial pressure region, it was concluded that the concentrations of HF and H2O in a fluoride melt are proportional to the partial pressure of each gas. The peak current due to the reduction of OH- ion could not be observed, though a clear peak current was observed when OH- ion was added to the melt and a cathodic scan was applied immediately. This indicates that OH- ion is unstable in a fluoride melt under HF-H2O atmosphere. (author)