CHEMICAL SCIENCE

Using 0.2 grams of lunar soil, they discovered the big secret


The first time I used lunar soil for an experiment, weighing 0.02 grams, Yao Yingfang, a professor at Nanjing University, was so nervous that her whole hand was shaking.

His research is to use some components of the lunar soil as artificial photosynthesis catalysts to make oxygen, hydrogen, methane and methanol from the carbon dioxide exhaled by humans and the water mined on the lunar surface.

If this skill can be mastered, even without the supply of the earth, human beings can use local materials on the moon to produce oxygen, water and other things necessary for survival. It could help humans build lunar bases and lunar relay stations to provide energy for more distant space exploration and interstellar travel.

Recently, the research team led by Academician Yang Mengfei, chief commander and chief designer of the Chang’e-5 probe system of the China Academy of Space Technology, Academician Wang Weihua of the Institute of Physics of the Chinese Academy of Sciences, and Academician Zou Zhigang of Nanjing University, proposed a strategy for extraterrestrial artificial photosynthesis on the moon. The research results were published in the authoritative international journal Joule.

Two methods were screened out to achieve efficient catalysis of lunar soil

In order to live and survive on the moon, water, oxygen and energy are indispensable, and transportation by the earth is always a drop in the bucket, and researchers hope to find more possibilities from the “indigenous” resources of the moon.

Two years ago, NASA announced the presence of water molecules on the lunar surface, and the Chang’e-5 probe launched by China has hammered the existence of water resources on the moon by exploring the lunar soil in situ.

Water is not only capable of being drunk by astronauts, but also transformed into two treasures. “We participated in a project led by the Qian Xuesen Space Technology Laboratory of the China Academy of Space Technology, called the mining of water resources on the lunar surface and photochemical conversion, that is, the decomposition of water into hydrogen and oxygen.” Yao Yingfang, the first author of the paper, said in an interview with China Science News.

After getting the lunar soil brought back by Chang’e 5, the team especially wanted to see whether the lunar soil as a catalytic material can also achieve water into hydrogen and oxygen, and whether the lunar soil can play a certain role in the conversion of carbon dioxide.

The lunar soil obtained this time is a very young basalt on the lunar surface, and this mineral is rich in catalyst components commonly used in artificial photosynthesis such as iron and titanium. “Through machine learning and other methods, we analyzed about 24 mineral components in the lunar soil, of which 8 components such as ilmenite, titanium oxide, hydroxyapatite, and a variety of iron-based compounds have good photocatalytic performance.” Yao Yingfang introduced.

Moreover, the surface of the lunar soil itself has a rich microporous and vesicle structure, which can further improve the catalytic performance of the lunar soil. It is very rare to find these natural advantages in the lunar soil.

In order to find the optimal solution, the research team conducted various attempts on lunar soil catalysis to evaluate its performance. For example, the conversion of hydrogen and oxygen is realized by electrolysis of water by photovoltaics; the decomposition of photocatalytic water into hydrogen and oxygen; the conversion of photocatalytic carbon dioxide into carbon monoxide, methane and methanol; and the photothermal catalysis of carbon dioxide hydrogenation to produce methane and methanol.

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Map of the extraterrestrial artificial photosynthesis process on the Moon. Courtesy of respondents

In the end, they screened out the photovoltaic electrolysis of water and the photothermal catalytic hydrogenation of carbon dioxide, which can achieve the highest catalytic efficiency of the lunar soil, and the resulting substances are more useful and pure.

“Methane, as a fuel, is a very good propellant for spacecraft; methanol is more widely used, and many organic compounds we wear and use have methanol as a raw material.” The continuous production of methanol means that we can build methanol chemical plants on the moon to realize the chemicals that humans need. Yao Yingfang said.

The four substances obtained by catalysis by lunar soil are oxygen, hydrogen, methane and methanol, which are all necessary for human beings to survive on the lunar surface and build bases and relay stations. As one of the richest resources on the moon, lunar soil resources have huge development space and potential.

In situ, greatly reducing the launch load and cost

Prior to this, scientists had proposed many strategies for extraterrestrial survival, but most designs relied on energy from Earth.

For example, the Mars Oxygen Field Resource Utilization Experimental Instrument (MOXIE), carried by NASA’s Perseverance Mars rover launched in 2020, can use carbon dioxide from the Martian atmosphere to produce oxygen, but the instrument relies on isotopic batteries from Earth to drive and realize the decomposition of carbon dioxide into carbon monoxide and oxygen through electrochemical methods under high temperature conditions.

“The standard they designed at the time was 10 grams of oxygen conversion efficiency per hour, but for various reasons, they eventually achieved a conversion efficiency of about 6 grams per hour on the surface of Mars.” Yao Yingfang said, “Not only is the efficiency not high, but it is also said that the device is still very bulky, and it is likely that the battery needs to be constantly replaced, which means that many times the spacecraft is launched, and each launch greatly increases the load.” ”

The extraterrestrial artificial photosynthesis technology in this paper is relatively simple, and it uses completely extraterrestrial resources and environments to produce oxygen, fuel and survival supplies.

The temperature of the moon at night is minus 173 degrees Celsius, and carbon dioxide will turn into dry ice at minus 78.5 degrees Celsius, so at night on the moon, carbon dioxide can be directly separated from the gas exhaled by humans, and then the water resources mined on the lunar surface are used to decompose hydrogen and oxygen, oxygen is for people to breathe, and carbon dioxide is put together with hydrogen. During the day, when the lunar temperature is as high as 127 degrees Celsius, the process of converting in situ carbon dioxide hydrogenation into methane can be cleverly realized.

“The biggest benefit of this is that it can significantly reduce the rocket launch load, reduce the cost of the spacecraft to fly to the moon and even farther into outer space, and can achieve a sustainable and sustainable deep space exploration.” Yao Yingfang said.

Analogous to the age of great navigation, the world has reached a consensus that in the near future, we will enter the era of great spaceflight. Moreover, there are already people who have gone to explore space one after another, such as Musk’s SpaceX company and Amazon founder Jeff Bezos.

Bao Weimin, academician of the Chinese Academy of Sciences and the International Academy of Astronautics, once estimated that by 2046, our total output value in the Earth-Moon Economic Zone will reach at least 10 trillion US dollars per year.

“If we want to conduct large-scale exploration of the extraterrestrial world, we must rely on the earth’s supplies as little as possible, and instead use extraterrestrial resources to achieve an extraterrestrial circulation system, so as to truly realize the Earth-Moon Space Economic Zone.” Yao Yingfang said, “Our strategy is to provide a ‘zero energy’ life support system for sustainable and affordable extraterrestrial living environments. ”

Precious 1 gram of lunar soil

July 12, 2021 is destined to be an unforgettable day for Yao Yingfang’s life. On this day, together with Academician Zou Zhigang, he went to the Lunar Exploration and Aerospace Engineering Center of the China National Space Administration to observe the ceremony of distributing the lunar soil. At the same time, as a member of the joint research team of the China Academy of Space Technology, the research team of Nanjing University conducted research on 1 gram of lunar soil.

“I was thrilled from start to finish! Before that, I never thought I would join such an honorable team, and we were the only joint research team among the first 13 scientific research units to issue lunar soils with materials, catalysis and energy as entry points. Whenever Yao Yingfang remembered that moment, she was still excited.

Don’t look at the moon soil used for research this time is only 1 gram, but it is very precious. It should be known that the moon soil that the American Apollo brought back from the moon and was given as a national gift to our leaders was only 0.5 grams.

After the moon is returned to Nanjing University, it is saved to the ultra-clean environment tailored by the school, which is strictly designed in accordance with the “Regulations on the Use of Lunar Samples” issued by the National Space Administration, with an oxygen content of not more than 20 ppm (parts per million, part per million rate) and a water vapor content of no more than 50 ppm. At the same time, the storage space must be monitored uninterruptedly and with zero dead angles, and real-time audio and video recordings and text records must be carried out during the experiment.

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Weigh the lunar soil in a strictly regulated environment. Courtesy of respondents

Yao Yingfang still clearly remembers the first time he used 0.02 grams of lunar soil, and a funny thing happened at that time. Yao Yingfang wanted his students to open this sacred moment, but he did not expect that the students were too excited to operate, and he was also extremely nervous when he personally went into battle, “When weighing 0.02 grams of moon soil, my whole hand was nervous to tremble, and the moon soil was too precious.” ”

The first stop settled in the Environmental Materials and Renewable Energy Research Center of Nanjing University is because there is a well-known extraterrestrial artificial photosynthesis research team at home and abroad, which gathers the top talents in China to do extraterrestrial artificial photosynthesis.

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Academician Zou Zhigang Provided by the interviewee

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Academician Zou Zhigang (third from right) and Professor Yao Yingfang (third from left) team take a group photo with Yueyang. Courtesy of respondents

The team not only includes Academician Zou Zhigang, academician Wang Weihua of the Institute of Physics of the Chinese Academy of Sciences, and Academician Yang Mengfei, chief commander and chief designer of the Chang’e-5 probe system of the China Academy of Space Technology, and the three academicians jointly built the academician studio of the physical and chemical process of extraterrestrial survival at the China Academy of Space Technology.

“It is based on this studio that we have the opportunity to receive such a valuable lunar soil, and this study used 0.2 grams of lunar soil.” Yao Yingfang said.

The research was done by Nanjing University in cooperation with the China Academy of Space Technology, the University of Chinese in Hong Kong (Shenzhen), and the University of Science and Technology of China, and the team members were very united and full of energy throughout the research process, and they had to report and exchange on the research process and progress every month. More importantly, they will also do their best to protect the originality of the lunar soil when conducting research, minimizing the loss caused by the research process.

Yao Yingfang revealed that they are looking for an opportunity to test the system in space, which may be verified in conjunction with China’s future manned lunar missions. (Source: China Science Daily Zhang Qingdan)

Related paper information:https://doi.org/10.1016/j.joule.2022.04.011



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