Electrochemically driven three-phase interlines into insulator compounds: electroreduction of solid SiO2 in molten...

Area of Science:

• Electrochemistry
• Materials Science
• Chemical Engineering

Background:

• Electrochemical reduction of silicon dioxide (SiO2) is a key process for silicon production.
• Understanding the mechanisms at the conductor|insulator|electrolyte interface is crucial for optimizing efficiency.

Purpose of the Study:

• To investigate the electrochemical reduction of solid SiO2 (quartz) to Si in molten CaCl2 at 1173 K.
• To develop and validate a novel penetration model for this electroreduction process.
• To analyze factors influencing the reduction rate, current efficiency, and energy consumption.

Main Methods:

• Potentiostatic electroreduction of cylindrical quartz pellets in molten CaCl2.
• Comparison of experimental data with a novel electrochemical penetration model.
• Analysis of diffusion and ohmic polarization effects in the generated porous silicon layer.

Main Results:

• Experimental results align well with the proposed penetration model.
• Reduction rate is primarily governed by O(2-) ion diffusion and ohmic polarization in the porous silicon layer.
• Cathodic passivation, likely due to CaO precipitation, retards the process at higher overpotentials.

Conclusions:

• The study provides a theoretical and experimental basis for optimizing silicon electroreduction.
• The developed model accurately describes the complex electrochemical reduction of SiO2.
• Understanding passivation mechanisms is critical for improving current efficiency and reducing energy consumption in silicon production.