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The active Martian water cycle, i.e. the presence of shallow water and soluble perchlorate salts in the Martian soil, enables the production of life-supporting hydrogen fuel and oxygen on Mars through the electrolysis of perchlorate brines. A team of scientists from Washington University in St. Louis has demonstrated an approach to produce ultra-pure hydrogen and oxygen from liquid Martian brines at minus 36 degrees Celsius (minus 32.8 degrees Fahrenheit).
This illustration shows Jezero Crater – the landing site of NASA’s Mars 2020 Perseverance rover – as it might have looked billions of years ago on Mars, when it was a lake. Image credit: NASA / JPL-Caltech.
“Our Martian brine electrolyser fundamentally changes the logistical calculation of missions to Mars and beyond,” said Professor Vijay Ramani, a researcher at the Center for Solar Energy and Energy Storage at Washington University in St. Louis.
“This technology is equally useful on Earth, where it opens up the oceans as a valuable source of oxygen and fuel.”
NASA’s Perseverance rover is en route to Mars now, carrying instruments that will use high-temperature electrolysis.
However, the MOXIE (Mars Oxygen In-Situ Resource Utilization Experiment) experiment will only produce oxygen, from carbon dioxide in the air.
The electrolyser developed by Professor Ramani and colleagues can produce 25 times more oxygen than MOXIE using the same amount of energy. It also produces hydrogen, which could be used to power the astronauts’ journey home.
“Our new brine electrolyzer incorporates a lead rutenate pyrochlore anode developed by our team in combination with platinum on a carbon cathode,” said Professor Ramani.
“These carefully designed components, coupled with the optimal use of traditional electrochemical engineering principles, have produced this high performance.”
The thoughtful design and unique anode allow the team’s electrolyser to function 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 that of Mars,” said Dr. Shrihari Sankarasubramanian, a researcher with the Center for Solar Energy and Energy Storage and the Department of Energy, Environmental and chemical engineering from Washington University in St. Louis.
“They prevent the water from freezing and also improve the performance of the electrolyser system by lowering the electrical resistance.”
Typically, water electrolyzers use highly purified deionized water, which adds to the cost of the system.
A system that can operate with suboptimal or salt water, such as the technology demonstrated by the team, can significantly improve the economic value proposition of water electrolysers everywhere, even right here on Earth.
“Having demonstrated these electrolyzers in challenging Martian conditions, we intend to deploy them under much milder conditions on Earth to use brackish or salt water to produce hydrogen and oxygen, for example, through seawater electrolysis,” said Dr. Pralay Gayen, a postdoctoral fellow in the Department of Energy, Environmental and Chemical Engineering at Washington University in St. Louis.
The team’s work was published in Proceedings of the National Academy of Sciences.
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Pralay Gayen et al. Collecting fuel and oxygen from the Martian regolith brine. PNAS, published online on 30 November 2020; doi: 10.1073 / pnas.2008613117
This article is based on a press release provided by Washington University in St. Louis.
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