New technology can get oxygen and fuel from saltwater from Mars

When it comes to water and Mars, there is some good news and some not so good. The good news: there is water on Mars! The bad news?

There is water on Mars.

The red planet is very cold; water that is not frozen is almost certainly full of salt from Martian soil, which lowers its freezing temperature.

You cannot drink salt water, and the usual method of using electricity (electrolysis) to break it down into oxygen (for breathing) and hydrogen (for fuel) requires removing the salt; a heavy and expensive business in a difficult and dangerous environment.

However, if oxygen and hydrogen could be directly driven out of brackish water, this process of electrolysis of brine would be much less complicated and less expensive.

Engineers at the McKelvey School of Engineering at Washington University in St. Louis have developed a system that does just that. Their research was published today in the Proceedings of the National Academy of Sciences (PNAS).

The research team, led by Vijay Ramani, professor emeritus Roma B. and Raymond H. Wittcoff in the Department of Energy, Environmental and Chemical Engineering, did not simply validate their brine electrolysis system under typical terrestrial conditions. ; the system was tested in a simulated Martian atmosphere at -33 F (-36 C).

“Our Martian brine electrolyzer is dramatically changing the logistical calculation of missions to Mars and beyond,” Ramani said. “This technology is also useful on Earth where it opens up the oceans as a viable source of oxygen and fuel”

In the summer of 2008, NASA’s Phoenix Mars Lander “touched and tasted” Martian water, vapors of melted ice unearthed by the lander. Since then, the European Space Agency’s Mars Express has discovered several underground ponds of water that remain in a liquid state thanks to the presence of magnesium perchlorate – salt.

To live – even temporarily – on Mars, let alone return to Earth, astronauts will need to make some of the basic necessities, including water and fuel, on the Red Planet. NASA’s Perseverance rover is now en route to Mars, carrying instruments that will use high-temperature electrolysis. However, the Mars Oxygen Resource In-Situ Use Experiment (MOXIE) will only produce oxygen from carbon dioxide in the air.

The system developed in Ramani’s lab can produce 25 times more oxygen than MOXIE using the same amount of energy. It also produces hydrogen, which could be used to fuel the return of astronauts.

“Our new brine electrolyzer incorporates a lead ruthenate pyrochlore anode developed by our team in conjunction with a platinum-on-carbon cathode,” said Ramani. “These carefully designed components, combined with the optimal use of traditional principles of electrochemical engineering, have resulted in this high performance.

The careful design and unique anode allow the system to operate without the need to heat or purify the water source.

“Paradoxically, the perchlorate dissolved in water, the so-called impurities, actually helps in an environment like Mars,” said Shrihari Sankarasubramanian, a research scientist in Ramani’s group and co-author of the article.

“They keep the water from freezing,” he said, “and also improve the performance of the electrolyzer system by lowering the electrical resistance.”

Typically, water chlorinators use highly purified deionized water, which increases the cost of the system. A system that can operate with “sub-optimal” or salt water, like the technology demonstrated by Ramani’s team, can dramatically improve the economic value proposition of water chlorinators anywhere, even here on planet Earth. .

“After demonstrating these electrolysers in demanding Martian conditions, we intend to deploy them also in much milder conditions on Earth to use brackish or salt water supplies to produce hydrogen and oxygen,” for example by electrolysis of seawater, ”said Pralay Gayen, postdoctoral research associate. in Ramani’s group and also co-author of this study.

Such applications could be useful in defense, creating oxygen on demand in submarines, for example. It could also provide oxygen as we explore uncharted environments closer to home on the high seas.

The underlying technologies enabling the brine electrolyzer system are the subject of a patent filing with the Office of Technology Management and are available for license from the university.