Electrochemical Production of Silicon Using an Oxygen-Evolving SnO2 Anode in Molten CaCl2-NaCl

Abstract

The electrochemical production of silicon from SiO2 in molten salts can reduce energy consumption and mitigate carbon emissions associated with the conventional carbothermic process. In this study, we compare the anodic behaviour of platinum, graphite, and tin oxide electrodes in molten CaCl2-NaCl-CaO-SiO2 at 850 °C using electrochemical methods including cyclic voltammetry, linear sweep voltammetry, and chronoamperometry. Pt exhibited low oxygen evolution overpotentials and no significant currents before OER, compared to SnO2. An eight-hour potentiostatic electrolysis with a SnO2 anode and a graphite cathode yielded a Si-Sn deposit, indicating partial dissolution of the SnO2 anode during the electrolysis process. These results highlight the kinetic trade-off of SnO2 relative to Pt, and the risk of Sn contamination with extended electrolysis times. While SnO2 is unsuitable for production of high-purity Si, it remains a promising anode candidate for Si-Sn alloy formation.