Mechanism of Electrolytic Reduction of SiO2 at Liquid Zn Cathode in Molten CaCl2

The reaction mechanism of electrolytic reduction of SiO2 at a liquid Zn cathode in molten CaCl2 was investigated with the aim of establishing a new production process of solar-grade Si. Three types of Zn/SiO2 contacting electrodes were prepared depending on the objectives. Cyclic voltammetry suggest...

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Bibliographic Details
Published in:Journal of the Electrochemical Society 2019, Vol.166 (6), p.D162-D167
Main Authors: Ma, Yuanjia, Ido, Akifumi, Yasuda, Kouji, Hagiwara, Rika, Homma, Takayuki, Nohira, Toshiyuki
Format: Article
Language:English
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Summary:The reaction mechanism of electrolytic reduction of SiO2 at a liquid Zn cathode in molten CaCl2 was investigated with the aim of establishing a new production process of solar-grade Si. Three types of Zn/SiO2 contacting electrodes were prepared depending on the objectives. Cyclic voltammetry suggested two reduction mechanisms of SiO2 at a Zn electrode. One is a direct electrolytic reduction that proceeds at potentials more negative than 1.55 V vs. Ca2+/Ca. The other is an indirect reduction by liquid Ca-Zn alloy at potentials more negative than 0.85 V. The both reduction mechanisms were confirmed to proceed at 0.60 V by electrolysis and immersion experiments. Impurity analysis by ICP-AES was conducted for the Si prepared by potentiostatic electrolysis at 0.60 V, and confirmed that the concentrations of the metal elements and P were lower than the target levels for primary Si before directional solidification process.
ISSN:1945-7111
DOI:10.1149/2.1211904jes