Overview of in-situ oxygen production technologies for lunar resources

The rich resources and unique environment of the Moon make it an ideal location for human expansion and the utilization of extraterrestrial resources. Oxygen, crucial for supporting human life on the Moon, can be extracted from lunar regolith, which is highly rich in oxygen and contains polymetallic oxides. This oxygen and metal extraction can be achieved using existing metallurgical techniques. Furthermore, the ample reserves of water ice on the Moon offer another means for oxygen production. This paper offers a detailed overview of the leading technologies for achieving oxygen production on the Moon, drawing from an analysis of lunar resources and environmental conditions. It delves into the principles, processes, advantages, and drawbacks of water-ice electrolysis, two-step oxygen production from lunar regolith, and one-step oxygen production from lunar regolith. The two-step methods involve hydrogen reduction, carbothermal reduction, and hydrometallurgy, while the one-step methods encompass fluorination/chlorination, high-temperature decomposition, molten salt electrolysis, and molten regolith electrolysis (MOE). Following a thorough comparison of raw materials, equipment, technology, and economic viability, MOE is identified as the most promising approach for future in-situ oxygen production on the Moon. Considering the corrosion characteristics of molten lunar regolith at high temperatures, along with the Moon's low-gravity environment, the development of inexpensive and stable inert anodes and electrolysis devices that can easily collect oxygen is critical for promoting MOE technology on the Moon. This review significantly contributes to our understanding of in-situ oxygen production technologies on the Moon and supports upcoming lunar exploration initiatives.