Kinetic Characteristics of Electrochemical Reduction of SiO 2 Granules in Molten CaCl 2

Abstract

The kinetic characteristics of electrochemical reduction of SiO2 granules in molten CaCl2 were investigated to develop a new process for producing solar-grade silicon. The reduction rate was evaluated based on the time dependence of the reduction fractions measured from the growth of the reduced Si layer and the weight change of the samples during electrolysis. The samples were prepared by potentiostatic electrolysis of SiO2 granules in molten CaCl2 at 1123 K. The results indicated that the reduction was fast at the initial stage of electrolysis, and gradually slowed as the reaction progressed. The apparent current density reached 0.7 A cm-2 at the initial stage, which was comparable to the commercial Hall-Héroult process for aluminum production. © 2014 The Electrochemical Society.