Silver catalysts may aid long-term space travel

Silver electrocatalysts may help enable long-term space travel, such as manned missions to Mars, by recovering oxygen from carbon dioxide, scientists say.
Despite continuous advances, major obstacles remain before manned missions can set off for destinations like Mars. A primary concern is how people will breathe.
Oxygen tanks cannot be shuttled out to resupply the astronauts, so the air must be recycled. Yet state-of-the-art systems are only about 50 per cent efficient at recovering used oxygen from carbon dioxide, researchers said.
NASA is funding several projects attempting to solve this problem, one of which involves Feng Jiao, assistant professor in University of Delaware's Department of Chemical and Biomolecular Engineering.

After Jiao and his colleagues published a paper in Nature Communications describing a silver electrocatalyst, a scientist at NASA's Glenn Research centre contacted them.
Jiao's team had created the silver electrocatalyst that, due to its carefully designed nanoscale structure, could convert carbon dioxide to carbon monoxide with 92 per cent efficiency - freeing oxygen in the process.

The catalyst itself is a silver coating on the surface of an electrode that increases the efficiency of the CO2-CO reaction by assisting with the transfer of electrons.
"The catalyst performance is definitely among the best. It's very selective, very efficient," Jiao said.

Carbon monoxide (CO) has many industrial applications, and the initial idea was to convert abundant CO2 to useful CO, with the oxygen as an incidental byproduct.
Jiao and the NASA scientist, Ken Burke, are co-principal investigators on a USD 750,000 NASA-funded grant, one of four teams trying to create the most efficient oxygen recycling system possible.
Burke's lab was working on a technology to convert two molecules of carbon monoxide to one molecule of carbon dioxide and one molecule of carbon.
If they can combine their systems, said Jiao, "then eventually we can completely split CO2 to one molecule of carbon and one molecule of oxygen."

With such a system, "in principle, we can recover 100 per cent of the oxygen from CO2. NASA is very interested in developing this kind of technology for deep space exploration," Jiao said.
The first challenge for the team is to convert the university laboratory's electrocatalysis device. The system currently processes its ingredients in batches, but for this purpose it must run continuously.
They then have to integrate their part of the work with what Burke's lab in Ohio has created.
If their system is one of the two chosen by NASA for further exploration, they will be granted USD 2 million to adapt the system for large-scale use.