Iron Production by the Use of Molten Salt Electrolysis

Steel is a fundamental structural material; however, its production poses significant environmental challenges, accounting for 4–5% of global carbon dioxide emissions. With an average carbon footprint of 1.9 tons of CO2 per ton of steel produced, the industry urgently requires sustainable alternatives. This research investigates electrolysis as a low-carbon substitute, categorizing these technologies by operating temperature: low-temperature aqueous hydroxide electrolysis (AHE), medium-temperature molten salt electrolysis (MSE), and high-temperature molten oxide electrolysis (MOE). In the MOE process, metal oxides decompose into molten metal and oxygen using inert (neutral) anodes. The findings indicate that iron oxide reduction in molten systems follows a stepwise mechanism: Fe2O3→Fe3O4→FeO→Fe. Key parameters, including current efficiency, applied voltage, and overpotential, significantly dictate overall energy efficiency. Furthermore, increasing the temperature and reducing the viscosity of the molten salt accelerates the reaction by facilitating oxygen ion transport. Finally, the presence of calcium oxide (CaO) on the cathode was found to shorten the reduction path and accelerate the process through the formation of calcium ferrite (Ca2Fe2O5).