In situ synchrotron X-ray diffraction study of the electrochemical reduction of SiO2 in molten CaCl2

In situ synchrotron X-ray diffraction was used to investigate the electrochemical reduction of SiO2 to Si in molten CaCl2 at 1123 K for the first time. The present technique enabled direct determination of intermediate products at high temperature, without cooling and washing treatments. Based on the diffraction data, the Ca2SiO4 phase was detected inside the electrode, but not at the electrode edge. These results were explained by the presence of different concentrations of O2− ions in molten CaCl2 permeating different regions of the electrode.