Dissolution Behavior of SiO2 and Electrochemical Reduction of Dissolved SiO2 in Molten Chlorides

Abstract

To develop a new production process for SOG-Si with high productivity and low energy consumption, the structure of silicate ions in molten eutectic NaCl–CaCl2 containing dissolved SiO2 was investigated by Raman spectroscopy. The existence of SiO3 2 − was indicated in melts containing 1.0 mol% of CaSiO3 (O2 −/SiO2 = 1.0). When 1.0 mol% of CaO was further added to the melt (O2 −/SiO2 = 2.0), the existence of SiO4 4 − was indicated. Cyclic voltammetry and potentiostatic electrolysis were conducted in molten NaCl–CaCl2 with different silicate ions. From cyclic voltammograms, XRD analysis, and SEM observation, silicate ions with different structure indicated different electrochemical reduction behavior; and the SiO3 2− ion is likely to be more suitable than SiO4 4− ion for the electrodeposition of Si.