Determination of Cell Potential for Silicon Electrodeposition

Electrowinning of Si from cryolite-based melts is a possible solution for mass production of high purity silicon. The required cell potential to deposit Si on a cathode of interest, copper, is fundamental information that needs to be measured for controlling the co-deposition of impurities. In this study, the potential was measured using cyclic voltammetry in a cryolite-6 pct SiO2 melt. The deposited Si on copper forms a Cu-Si alloy in which the activity of Si affects the decomposition potential. The measurements were carried out in a range of Si concentrations, allowing the prediction of potential change during the actual deposition process, where the Si content changes constantly. The results were compared with the values obtained from cyclic voltammetry on an inert electrode, graphite, to investigate if the formation of Cu-Si alloy is responsible for decreasing the potential.