Kinetic and Passivation Limitations in Titanium Reduction via Molten Oxide–Fluoride Electrolysis

Molten oxide–fluoride electrolysis enables direct metal extraction from ores while producing only oxygen. Titanium and its alloys are highly valued for their exceptional high‐ and low‐temperature properties, enabling broad applications in metallurgy and other fields. However, the direct electrolytic deposition of titanium from its oxides via molten oxide electrolysis is a significant challenge. This article systematically investigates the limitations of this process in a CaF ₂ –CaO–TiO ₂ melt. Electrochemical experiments were conducted using tungsten and iron electrodes with Fe ₂ O ₃ deposition; in all cases, no significant metallic titanium deposition was observed. Cyclic and square‐wave voltammetry analyses revealed a multistep reduction mechanism. Results show negligible Ti deposition on the W electrode and only micrometer‐thick layers on the Fe electrode or with Fe ₂ O ₃ . The primary limiting factors are the following: (1) The reduction rate of titanium ions is close to the dissolution rate of metallic titanium (both ~10 ⁻⁴ cm·s ⁻¹ ) and (2) rapid formation of CaTiO ₃ passivates the cathode, impeding continuous Ti deposition, with CaTiO ₃ reduction as the rate‐controlling step. This article clarifies the fundamental barriers to efficient Ti extraction via molten oxide–fluoride electrolysis and offers strategic insights for optimizing titanium metallurgy from mineral sources.