Raman Analysis and Electrochemical Reduction of Silicate Ions in Molten NaCl-CaCl2

This study investigated the ionic species and electrochemical reduction of silicate ions at a solid graphite electrode in molten NaCl-CaCl2 eutectic melts with various concentrations of O2- ion at 1023 K. Silicate ion species in the melts with various O2-/SiO2 ratios (r(O2-/SiO2)) r(O2-/SiO2) = 1.0, and SiO44- for r(O2-/SiO2) = 1.5 and 2.0. From cyclic voltammetry, XRD, and SEM analyses, electrochemical reduction was indicated for SiO32- and SiO44- at more negative than 1.0 V and 0.80 V vs Na+/Na, respectively. Formation of CaSi2 was confirmed at 0.50 V in all molten salts with r(O2-/SiO2) = 1.0, 1.5, and 2.0. The potential ranges for pure Si deposition are almost the same in molten salts with r(O2-/SiO2) = 1.0 and 1.5.(c) 2021 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BYNC-ND, http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email: permissions@ioppublishing.org.