Electrochemical Studies on Ag, Fe, and Cu Species in AlCl[sub 3]-NaCl Melts

Abstract
The electrochemical behavior of the Ag/Ag+, Fe/Fe2+, Fe2+/Fe3+ , and Cu/Cu+, Cu+/Cu2+ systems in the equimolar region of has been investigated using potentiometry, pulse polarography, cyclic voitammetry, chronoamperometry, and chronopotentiometry. In contrast to the Al electrode, the emf of the Ag+/Ag electrode was found to be virtually independent of the melt composition. The Ag+ was found to undergo reversible deposition at a tungsten electrode. However, in cyclic voltammetric experiments, the stripping process showed a marked dependence on Ag+ concentration, temperature, and sweep rate. Possible explanations for this dependence are presented. The diffusion coefficient for Ag+ at 175δC was found to be . The Fe3+/Fe2+ couple was found to be reversible while the Fe2+/Fe couple showed typical deposition‐stripping behavior. Above an initial concentration of 5 mM the deposition process became concentration independent while the stripping process was found to involve two different electrode reactions. This behavior was consistent with the low solubility of in the equimoiar region. Nernst plots for the anodization of Cu gave low n‐values in Cl‐rich melts, while n‐values of 1 were obtained in ‐rich melts. These results are best explained by introducing the following equilibrium reaction for which a value of was calculated for . The two Cu couples were well behaved electrochemically.