STEP Iron, a Chemistry of Iron Formation without CO2 Emission: Molten Carbonate Solubility and Electrochemistry of Iron Ore Impurities

The unexpected solubility of iron oxides in lithium carbonate electrolytes, coupled with facile charge transfer and a sharp decrease in iron electrolysis potentials with increasing temperature, provides a new route for iron production. Iron is formed without an extensive release of CO2 in a process compatible with the predominant naturally occurring iron oxide ore, hematite, Fe2O3. In this study, we demonstrate that iron is an effective cathode media and that nickel and iridium are effective anodes in the electrolytic formation of iron in molten carbonates, and each can sustain current densities of IA cm(-2). Silicate and aluminate impurities found in common iron ores are soluble in molten lithium carbonate and do not adversely affect the iron formation by electrolysis. The solubility of lithium oxide in molten carbonate is found to be unexpectedly high (similar to 50 mol %), and the presence of high concentrations of lithium oxide decreases the potential required for the electrolytic formation of iron or carbon. Iron, a basic commodity, currently accounts for the release of one-quarter of worldwide CO2 emissions by industry. The endothermic nature of the new synthesis route provides an effective vehicle for the solar efficient, CO2-free, production of iron as a STEP process.