The Electrochemical Behavior of Aluminum in the Low Temperature Molten Salt System n Butyl Pyridinium Chloride: Aluminum Chloride and Mixtures of This Molten Salt with Benzene

Abstract

The aluminum deposition and stripping processes at tungsten, platinum, and glassy carbon electrodes in the low temperature molten salt system, n butyl pyridinium chloride: aluminum chloride, and the 50 volume percent (v/o) mixture of this molten salt with benzene have been investigated, using a variety of electrochemical techniques. At all three electrodes, and in both solvent systems, the deposition reaction in slightly acidic melts, the reduction of ions, was found to involve a nucleation process while at the tungsten and platinum electrodes underpotential deposition was also observed. Reduction of the n butyl pyridinium cation was found to occur at −1.1V vs. Al(2:1 melt) which is positive of the reduction potential of ions and therefore aluminum deposition in basic melts was not observable. Studies of the stripping of aluminum from inert substrates showed that aluminum is very slowly corroded in acidic melts, and melt‐benzene mixtures, by traces of oxidizing impurities while in basic systems aluminum reduces the n butyl pyridinium cation. Potentiometric titration of the 50 v/o melt‐benzene mixture showed that the acid‐base properties of this system are defined, as in the pure melt, by the equilibrium