Electrochemical Behavior of Si(IV) on the Mo Electrode in the CaCl2–CaF2–CaO–SiO2 Melt

Abstract

This work concerns a study on investigating the electrochemical behaviors of silicon using the molybdenum electrode in molten CaCl2–CaF2–CaO–SiO2 at 1023 K, by means of linear scan voltammetry, square wave voltammetry, chronoamperometry, open circuit chronopotentiometry, reversal chronopotentiometry and polarization curve. The results based on the linear scan voltammetry showed that reduction of Si(IV) in CaCl2–CaF2–CaO–SiO2 melt proceeds in a single step exchanging four electrons, which is a reversible process with diffusion-controlled mass transfer, and the diffusion coefficient for the reduction process of Si(IV) ions in CaCl2–CaF2–CaO (3.68 wt %)–SiO2 (4 wt %) is about 1.11 × 10−4 cm2 s−1, at 1023 K. The reversibility of the Si(IV)/Si redox couple on the molybdenum electrode is confirmed via linear scan voltammetry. Chronoamperometric measurements indicated that the I–t transients of Si(IV) follow instantaneous nucleation with varied the applied overpotential. Furthermore, the sample deposited on the molybdenum electrode using potentiostatic electrolysis was identified by X-ray diffraction (XRD). The XRD result indicates that the obtained deposits were Si and MoSi2.