Application and Corrosion Resistance of Fe-Ni Inert Anodes in Oxygen Extraction from Lunar Regolith by Molten Salt Electrolysis

The development of inert anodes is one of the key challenges requiring resolution in cryolite molten salt electrolysis technology to extract oxygen from lunar regolith. To address the severe corrosion and oxidation challenges faced by oxygen-evolving anodes during electrolysis, the 43Fe-57Ni alloy is investigated and a surface passivation method is proposed. This method involves pre-oxidation treatment at 950°C in air to form a dense passivation layer on the anode surface. Within this layer, the generation of NiFe₂O₄ is crucial for enhancing the anode's corrosion and oxidation resistance. Results from galvanostatic electrolysis and linear voltammetry scans demonstrate that the passivation layer formed on the alloy anode surface during electrolysis effectively protects the substrate. Within the current density range of 0.6～1.0 A/cm², the passivation layer maintains a state of dynamic stability, adheres tightly to the anode substrate, and significantly mitigates corrosion in the cryolite. When applied in the cryolite molten salt electrolysis system for oxygen production from lunar regolith, the 43Fe-57Ni alloy anode achieved an average oxygen production rate of 1.61 g/h, an average anodic current efficiency of 85.74%, and an average oxygen purity of 91.66%. These results confirm the application potential of this alloy anode in lunar soil electrolysis for oxygen production technology.