Electrochemical Behaviour of Silicon Ions in NaCl-KCl Mixture with Low KF Concentration

Abstract

In this work, we studied the electrochemical behaviour of silicon ions in NaCl-KCl-KF molten salts containing K₂SiF₆ at 1003 K. Electrochemical techniques such as cyclic voltammetry, chronopotentiometry and chronoamperometry were used to study the kinetics of Si deposition on molybdenum working electrode. The diffusion coefficient and nucleation mode of silicon ions were investigated. The nucleation mode of Si ions was determined to be instantaneous nucleation by chronoamperometry. The diffusion coefficient of Si ions is 0.32 × 10^–5 cm².s⁻¹ and 1.21 × 10^–5 cm².s⁻¹ from cyclic voltammetry and chronopotentiometry, respectively. Before Si film formation, MoSi₂ layer is formed on the Mo electrode. Electrolysis was performed in potentiostatic and galvanostatic modes. SEM, EDS and XRD analysis was performed on cathode products. At low cathode current densities, only MoSi₂ is formed, whereas MoSi₂ layer formation followed by thick Si film deposition takes place at high current densities.