Electrochemical Behavior of Silicon Species in Cryolite Melt

Electrodeposition of Si from cryolite based melts is a possible solution for mass production of solar grade silicon. The deposition potential of Si on the candidate cathode, such as graphite, is fundamental information that needs to be measured and applied to restrict the co–deposition of impurities. In this study this potential was measured using cyclic voltammetry. As the activity of SiO2 in the electrolyte affects the deposition potential, the measurements were carried out in a range of SiO2 concentrations, allowing the prediction of potential change during the actual deposition process, where the SiO2 content undergoes fluctuations. The kinetics of the oxidation and reduction reactions were also studied using the recorded voltammograms, showing that reduction of Si is a two steps process controlled by diffusion.