Cathodic process in NaCl-KCl-Al2S3 molten salts

The electrolysis of Al 2 S 3 in NaCl-KCl molten salts is one of effective ways to achieve sustainable and low-carbon aluminum preparation. The dissolution of Al 2 S 3 into a chloride molten salt promotes the generation of Al-S-Cl complex ions. In this study, the discharge complex ions present in the equimolar NaCl-KCl salt with 1 wt% Al 2 S 3 were analyzed via quantum chemistry calculations at 953 K. On this basis, the cathodic electrochemical behaviors were experimentally investigated via linear sweep voltammetry and chronoamperometry. The results show that Al 2 S 3 Cl − complex ions are discharged on the graphite cathode through a one-step, three-electron transfer reduction process. This reduction is diffusion-controlled and exhibits a quasi-reversible process, with a charge transfer coefficient of 0.271 and a diffusion coefficient of 7.500 × 10 −5  cm 2 ·s −1 .