Sikirić M., Choquet P., Philippe A.M., Valle N., Hadler K., Bjelajac A., Chemin J.B., Kadok J., Bulou S.
Vacuum, vol. 240, art. no. 114508, 2025
To establish a permanent settlement on the Moon, it is essential to find solutions for producing oxygen (O<sub>2</sub>) and water (H<sub>2</sub>O). One promising method is the in-situ production of H<sub>2</sub>O through the thermal reduction of lunar regolith containing iron oxide (Fe<sub>2</sub>O<sub>3</sub>). This study explores the use of Electron Cyclotron Wave Resonance (ECWR) plasma for reducing Fe<sub>2</sub>O<sub>3</sub>, comparing its energy efficiency to traditional hydrogen (H<sub>2</sub>) thermal reduction. Experiments were conducted using an H<sub>2</sub>/Ar plasma mixture on Fe<sub>2</sub>O<sub>3</sub> thin films at varying substrate temperatures and treatment times. Characterization techniques revealed a multilayer structure forming during the reduction, with a rapid transition to metallic iron (Fe) on the surface after 15 min of treatment. An intermediate Fe<sub>3</sub>O<sub>4</sub> layer developed with extended reduction time, resulting in a distinct three-layered structure. Controlled heating above 200 °C significantly accelerated the reduction process while maintaining the same mechanism. Energy efficiency calculations indicate that H<sub>2</sub>/Ar ECWR plasma can be up to six times more efficient than simple thermal reduction, highlighting its potential as an effective method for lunar oxygen production.
