Cathodic Potential Dependence of Electrochemical Reduction of SiO2 Granules in Molten CaCl2
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- 作者：Xiao Yang ; Kouji Yasuda ; Toshiyuki Nohira…
- 刊名：Metallurgical and Materials Transactions E
- 出版年：2016
- 出版时间：September 2016
- 年：2016
- 卷：3
- 期：3
- 页码：145-155
- 全文大小：2,616 KB
- 刊物类别：Metallic Materials; Characterization and Evaluation of Materials; Structural Materials; Surfaces and
- 刊物主题：Metallic Materials; Characterization and Evaluation of Materials; Structural Materials; Surfaces and Interfaces, Thin Films; Nanotechnology; Energy, general;
- 出版者：Springer US
- ISSN：2196-2944
- 卷排序：3
文摘
As part of an ongoing fundamental study to develop a new process for producing solar-grade silicon, this paper examines the effects of cathodic potential on reduction kinetics, current efficiency, morphology, and purity of Si product during electrolysis of SiO2 granules in molten CaCl2 at 1123 K (850 °C). SiO2 granules were electrolyzed potentiostatically at different cathodic potentials (0.6, 0.8, 1.0, and 1.2 V vs Ca2+/Ca). The reduction kinetics was evaluated based on the growth of the reduced Si layer and the current behavior during electrolysis. The results suggest that a more negative cathodic potential is favorable for faster reduction. Current efficiencies in 60 minutes are greater than 65 pct at all the potentials examined. Si wires with sub-micron diameters are formed, and their morphologies show little dependence on the cathodic potential. The impurities in the Si product can be controlled at low level. The rate-determining step for the electrochemical reduction of SiO2 granules in molten CaCl2 changes with time. At the initial stage of electrolysis, the electron transfer is the rate-determining step. At the later stage, the diffusion of O2− ions is the rate-determining step. The major cause of the decrease in reduction rate with increasing electrolysis time is the potential drop from the current collector to the reaction front due to the increased contact resistance among the reduced Si particles.Manuscript submitted January 19, 2016.