Cyclic Voltammetry Study of Anodic and Cathodic Reactions on Graphite in Cryolite-Silica 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 measurement was carried out in a range of SiO2 concentration, 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.