Yttria-Stabilized Zirconia Assisted Green Electrochemical Preparation of Silicon from Solid Silica in Calcium Chloride Melt

A novel integrated cell with O2-|YSZ|Pt|O-2(air) reference and counter electrodes was constructed using a short yttria-stabilized zirconia solid electrolyte (YSZ) tube. Combining with cyclic voltammetry and potentiostatic electrolysis methods, green electrochemical preparation of Si from solid SiO2 in CaCl2 melt at 1173 K was studied via an experimental apparatus containing the novel integrated cell under completely carbon-free conditions; the effect of electrolysis time on the morphology of the Si product was also investigated by scanning electron microscopy with energy dispersive x-ray spectroscopy (SEM-EDS). The results show that the morphology of the product obtained from potentiostatic electrolysis at a low overpotential (- 1.6 V) undergoes an evolution from SiO2 raw powder with different sizes to aggregates of spherical particles and small particles with partial reduction, and then to Si nuclei, and finally to Si wires or flakes. The morphology of electrolytic products has little relation with that of SiO2 raw powder and may be controlled by applying different potentials. Furthermore, the longer the electrolysis time, the more the Si wires grow, and the higher the Si purity overall. It is feasible that the experimental apparatus without the sealed stainless steel reactor and any carbonaceous materials can be used to prepare Si from solid SiO2 in CaCl2 melt and release O-2 gas at the same time.

Automated summary

In this study, a novel integrated cell structure was successfully used to investigate the green electrochemical synthesis of silicon from solid SiO2 in a CaCl2 melt at 1173 K. It was found that the electrolysis time affects the morphology and purity of the silicon product. The results indicate that the morphology of the silicon product can be controlled by adjusting the potential, and with longer electrolysis time, the purity and growth morphology of silicon change accordingly.