LAUSR

20 The reaction mechanism of electrolytic reduction of SiO2 at a liquid Zn cathode 21 in molten CaCl2 was investigated with the aim of establishing a new production process 22 of solar-grade Si. Three types of Zn/SiO2 contacting electrodes were prepared 23 depending on the objectives. Cyclic voltammetry suggested two reduction mechanisms 24 of SiO2 at a Zn electrode. One is a direct electrolytic reduction that proceeds at 25 potentials more negative than 1.55 V vs. Ca 2+ /Ca. The other is an indirect reduction by 26 liquid Ca–Zn alloy at potentials more negative than 0.85 V. The both reduction 27 mechanisms were confirmed to proceed at 0.60 V by electrolysis and immersion 28 experiments. Impurity analysis by ICP-AES was conducted for the Si prepared by 29 potentiostatic electrolysis at 0.60 V, and confirmed that the concentrations of the metal 30 elements and P were lower than the target levels for primary Si before directional 31 solidification process. 32