Properties of fused polysulphides—V. voltammetric studies on sulphur and polysulphides in fused KSCN and LiCl-KCl eutectic

The oxidation of alkali metal polysulphides in fused KSCN and LiCl/KCl eutectic has been studied by cyclic voltammetry and potential step techniques. Sulphur was found to be the final oxidation product. For solutions in KSCN at 210°C only one oxidation peak was observed, involving a common, one-electron electrochemical process for all the polysulphides in the composition range M2S3-M2S6. It is proposed that the common electroactive species leading to the formation of the sulphur deposit is S−2 or S−3. The anodic formation of sulphur was found to be diffusion controlled, and no inhibition due to the formation of a poorly-conducting liquid phase was apparent. The cathodic dissolution of sulphur was studied in both solvents. It resembles the anodic dissolution of a metal, giving rise to characteristics stripping peaks in the cyclic voltammograms.