Electrochemical Reduction of SiO2 Granules to One-Dimensional Si Rods Using Ag-Si Eutectic Alloy

초록

Producing solar grade silicon using an inexpensive method is a key factor in lowering silicon solar cell costs; the direct electrochemical reduction of SiO2 in molten salt is one of the more promising candidates for manufacturing this silicon. In this study, SiO2 granules were electrochemically reduced in molten CaCl2 (850 degrees C) using Ag-Si eutectic droplets that catalyze electrochemical reduction and purify the Si product. When Ag is used as the working electrode, the Ag-Si eutectic mixture is formed naturally during SiO2 reduction. However, since the Ag-Si eutectic droplets are liquid at 850 degrees C, they are easily lost during the reduction process. To minimize the loss of liquid Ag-Si eutectic droplets, a cylindrical graphite container working electrode was introduced and Ag was added separately to the working electrode along with the SiO2 granules. The graphite container working electrode successfully prevented the loss of the Ag-Si eutectic droplets during reduction. As a result, the Ag-Si eutectic droplets acted as stable catalysts for the electrochemical reduction of SiO2, thereby producing one-dimensional Si rods through a mechanism similar to that of vapor-liquid-solid growth.

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