The electrochemical behavior of Al 2S 3 in molten MgCl 2 + NaCl + KCl eutectic

Abstract

The electrochemical behavior of Al 2S 3 in MgCl 2 + NaCl + KCl eutectic has been studied at graphite electrodes at 1023 K using the technique of linear sweep voltammetry. The electrolytic decomposition of Al 2S 3 in the eutectic involves the cathodic reduction of aluminum ions (or aluminum-ion-containing species) and the anodic oxidation of sulfide ions (or sulfide-ion-containing species). The reduction has been found to proceed by a reversible, three-eletron transfer that forms an insoluble product. The average apparent diffusion coefficient for aluminum ions during deposition is 1.03 × 10 −5 cm 2 s −1. The oxidation involves the two-electron discharge of sulfide ions (S 2− ⇌ S + 2 e), followed by the dimerization of sulfur atoms to S 2 (S + S ⇌ S 2), which is very fast and very much displaced towards S 2. The average apparent diffusion coefficient for sulfide ions is calculated to be 2.73 × 10 −5 cm 2 s −1.