Low-temperature Molten Salt Electrolysis for Lunar Regolith Reduction

The electrochemical reduction of lunar regolith dissolved in molten salts presents a promising pathway for the extraction of oxygen and metals on the Moon. Electrolytes with low melting points would not only reduce the energy consumption of the process but also minimize the thermal wear on equipment, leading to longer operational lifetimes. This work focuses on the experimental testing of a low-temperature electrolyte capable of effectively reducing all metal cations present in lunar regolith, avoiding bath poisoning. Cyclic voltammetry was conducted in FLiNaK electrolytes (melting point of 454°C) to investigate the electroactivity of Ca²⁺ ions. The focus was on calcium since it is the metal with the highest redox potential among the main constituents of the lunar regolith. The findings showed that eutectic alkali metal fluoride mixtures are suitable candidates for sustainable lunar molten salt electrolysis in which all metals, including Ca, can be reduced. Subsequently, galvanostatic electrolysis of lunar anorthosite simulant in molten FLiNaK at different temperatures showed the potential of selectively depositing metals, particularly silicon, on molybdenum electrodes. The cathodic products were characterized via SEM-EDS.