Depolarization behavior of Ti deposition at liquid metal cathodes in a NaCl-KCl-kF melt

Owing to the low-cost and fast process, molten salt electrolysis is considered as a novel method to replace the Kroll process for preparing titanium. However, this process has not been fully realized because of the multi-step reduction and complicated disproportionation behaviors of multivalent titanium ions in melt. To address such critical problems, here we use liquid metals (Sn and Pb) as the cathode instead of solid metal cathode (Mo) during the electrolysis, in which the reduction process of Ti³⁺ (TiF₆ ³⁻) becomes a simple one-step process (Ti³⁺ + 3e = Ti (alloys)). Also, the deposition potential is more positive (>0.5 V) than that using solid Mo, owing to the depolarizing effect of the liquid metals. One-step process and depolarization behavior are favorable to increase the current efficiency, effectively decreasing the power consumption in comparison with the conventional electrolysis at solid metal cathodes. Similar to the electrolytic production of aluminum in Hall-Heroult system, there would be a continuous electrolysis process because the product is liquid alloy in this system.