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Pinpoint and bulk electrochemical reduction of insulating silicon dioxide to silicon

Nature Materials volume 2, pages 397–401 (2003)Cite this article

Abstract

Silicon dioxide (SiO2) is conventionally reduced to silicon by carbothermal reduction, in which the oxygen is removed by a heterogeneous–homogeneous reaction sequence at approximately 1,700 °C. Here we report pinpoint and bulk electrochemical methods for removing oxygen from solid SiO2 in a molten CaCl2 electrolyte at 850 °C. This approach involves a 'contacting electrode', in which a metal wire supplies electrons to a selected region of the insulating SiO2. Bulk reduction of SiO2 is possible by increasing the number of contacting points. The same method was also demonstrated with molten LiCl-KCl-CaCl2 at 500 °C. The novelty and relative simplicity of this method might lead to new processes in silicon semiconductor technology, as well as in high-purity silicon production. The methodology may be applicable to electrochemical processing of a wide variety of insulating materials, provided that the electrolyte dissolves the appropriate constituent ion(s) of the material.

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Figure 1: Photographs of the two types of contacting electrodes.
Figure 2: Cyclic voltammograms of Mo, Si and SiO2 contacting electrodes in molten CaCl2 at 850 °C.
Figure 3: The potential dependence of the electrolytic reduction of SiO2.
Figure 4: Pinpoint electrolytic reduction of SiO2.
Figure 5

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Acknowledgements

We are grateful to L. O. Jerdal for discussions. This study was supported by Yazaki Memorial Foundation for Science and Technology.

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  1. Department of Fundamental Energy Science Graduate School of Energy Science, Graduate School of Energy Science, Kyoto University, Sakyo-ku, 606-8501, Kyoto, Japan

    Toshiyuki Nohira, Kouji Yasuda & Yasuhiko Ito

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  1. Toshiyuki Nohira
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Correspondence to Toshiyuki Nohira.

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Nohira, T., Yasuda, K. & Ito, Y. Pinpoint and bulk electrochemical reduction of insulating silicon dioxide to silicon. Nature Mater 2, 397–401 (2003). https://doi.org/10.1038/nmat900

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