Secrets of lunar soil: Oxygen and fuel may be produced on the moon

Science and Technology Daily reporter Jin Feng

A new paper in the international academic journal Joule has attracted widespread attention in the academic community. After a detailed analysis of the elements and mineral structure of the lunar soil retrieved by Chang'e-5 (hereinafter referred to as Chang'e-5 lunar soil), the research team found that some active compounds in the lunar soil have good catalytic properties. They used it as a catalyst, used artificial photosynthesis technology, and used simulated sunlight to convert water and carbon dioxide into oxygen, hydrogen, methane, and methanol.

"Lunar soil is one of the most abundant resources on the moon. If lunar soil or its extracted components can be used as artificial photosynthesis catalysts on the moon, the payload and cost of spacecraft can be greatly reduced. In the future, perhaps we can use local materials on the moon to provide life support for astronauts and prepare fuel." On May 7, in an exclusive interview with Science and Technology Daily, Yao Yingfang, co-first author of the paper and professor at Nanjing University, expressed this outlook.

The elemental composition and micro-nanostructure of lunar soil give it good catalytic properties

In 2021, Nanjing University, as one of the members of the joint team led by the China Academy of Space Technology, received the first 1 gram of lunar samples. The research team that published the results this time used 0.2 grams of them for research and discovered some characteristics of the lunar soil.

"The Chang'e-5 lunar soil comes from very young basalt on the lunar surface. This mineral is rich in iron, titanium and other catalyst components commonly used in artificial photosynthesis. The team used machine learning and other methods to conduct multiple analyses of the lunar soil structure and found that eight crystalline minerals, including ilmenite and titanium oxide, can perform well in artificial photosynthesis. "said Yao Yingfang.

What is the actual catalytic performance of lunar soil? The research team used lunar soil as a catalytic material for photovoltaic water electrolysis, photocatalytic water decomposition, photocatalytic carbon dioxide reduction, photothermal catalytic carbon dioxide hydrogenation and other reactions, and found that it has high performance and selectivity in photovoltaic water electrolysis and photothermal catalytic carbon dioxide hydrogenation reactions.

"In these experiments, we applied simulated sunlight, used water and carbon dioxide as raw materials, and compared the lunar soil with the simulated lunar soil retrieved by the US Apollo program and the basalt on the earth's surface. We found that in the photovoltaic electrolysis of water reaction, the Chang'e-5 lunar soil was the most efficient in producing oxygen and hydrogen. In the photothermal catalytic carbon dioxide hydrogenation reaction, the efficiency of methane and methanol produced by the Chang'e-5 lunar soil was also higher than that of other materials." Yao Yingfang happily stated that oxygen can provide life support for humans, methane is an active ingredient in rocket propellant, and methanol is a raw material for organic chemicals.

The study also found that the surface of the lunar soil has abundant micropores and vesicle structures. "This micro-nano structure further improves the catalytic performance of the lunar soil," said Yao Yingfang.

We will strive to carry experiments in future space programs

Based on the above analysis, the research team proposed strategies and steps to achieve extraterrestrial artificial photosynthesis using lunar soil in response to the lunar environment. "Use the extremely low temperature of about -173°C on the moon at night to condense and separate carbon dioxide from the air humans breathe. Then use sunlight to use the Chang'e-5 lunar soil as an electrocatalyst for water decomposition and a photothermal catalyst for carbon dioxide hydrogenation to convert human exhaled waste gas and water resources mined on the lunar surface into oxygen, hydrogen, methane and methanol." Yao Yingfang said that using extraterrestrial artificial photosynthesis technology, perhaps only solar energy, water and lunar soil on the moon are needed to produce oxygen and hydrocarbons. This technology is expected to achieve low energy consumption and high-efficiency energy conversion with the help of the temperature environment on the lunar surface. This provides a potential solution for establishing an in-situ resource utilization system that adapts to the extreme environment of the moon.

Although the catalytic efficiency of lunar soil is lower than that of catalysts available on Earth, Yao Yingfang said that the research team will also separate and refine the effective catalytic components in the lunar soil in an effort to achieve better catalytic effects.

However, whether the extraterrestrial artificial photosynthesis technology can be realized in the real lunar environment still needs further verification. Yao Yingfang introduced that at present, they are working with researchers from the China Academy of Space Technology to strive to realize the extraterrestrial artificial photosynthesis technology in future space programs for testing and real environment verification.

Source: Science and Technology Daily Author: Jin Feng