The active water cycle of Mars, ie the presence of shallow water and soluble perchlorate salts in the soil of Mars, enables the production of hydrogen fuel and life-sustaining oxygen on Mars by electrolysis of perchlorate brines. A team of scientists from Washington University in St. Louis has demonstrated an approach to produce ultrapure hydrogen and oxygen from liquid Martian brine 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 looked on Mars billions of years ago, when it was a lake. Image credit: NASA / JPL-Caltech.
“Our Mars brine electrolyser is radically changing the logistical calculus 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 viable source of oxygen and fuel.”
NASA’s Perseverance rover is now on its way to Mars, with instruments using high-temperature electrolysis.
However, the Mars Oxygen In-Situ Resource Utilization Experiment (MOXIE) will only produce oxygen from the carbon dioxide in the air.
The electrolyzer developed by Professor Ramani and colleagues can produce 25 times more oxygen than MOXIE with the same amount of power. It also produces hydrogen, which can be used to fuel the astronauts’ journey home.
“Our new brine electrolyser contains a lead ruthenate pyrochloro anode developed by our team in combination with platinum on carbon cathode,” said Professor Ramani.
“These carefully designed components coupled with the optimal use of traditional electrochemical engineering principles have delivered this high performance.”
The careful design and unique anode allow the team’s electrolyser to function without the need to heat or purify the water source.
“Paradoxically, the dissolved perchlorate in the water, called impurities, helps in an environment like that of Mars,” says Dr. and Chemical Engineering at Washington University in St. Louis.
“They prevent the water from freezing and also improve the performance of the electrolyzer system by lowering electrical resistance.”
Water electrolysers usually use highly purified, deionized water, which adds to the cost of the system.
A system that can operate with sub-optimal or salt water, like the technology demonstrated by the team, can significantly improve the economic value proposition of water electrolysis devices everywhere – even here on Earth.
“Now that we have demonstrated these electrolysis devices under demanding Mars conditions, we plan to deploy them also 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, Environment and Chemical Technology at Washington University in St. Louis.
The team’s work is published in the Proceedings of the National Academy of Sciences.
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Pralay Gayen et al. Harvesting fuel and oxygen from regolithic brine from Mars. PNAS, published online November 30, 2020; doi: 10.1073 / pnas.2008613117
This article is based on a press release from Washington University in St. Louis.
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