Friday, September 12, 2014

Water-splitter could make hydrogen fuel on Mars

Making fuel on site for a return trip to Mars may be a step closer. A cunning way to split water into oxygen and hydrogen in two distinct steps could be a boon to both astronauts and future Earthlings, enabling them to use renewable energy sources for making hydrogen fuel.

Hydrogen fuel cells can power vehicles ranging from cars to submarines and rockets. They can also heat buildings, and double as portable power-packs for computers or other kit used in the field. But existing methods for creating usable hydrogen gas from water require a lot of electricity. That means renewable energy sources like wind or sunlight, which are often patchy, are not reliable enough.

It can also be hazardous to scale up "artificial leaves", which lmake fuel from sunlight, just like plants, says Lee Cronin at the University of Glasgow, UK. This is because the low powers available don't produce the gases quickly enough to keep them apart once they form. "All they do is build up oxygen and hydrogen until they explode," he says.

Cronin and his colleagues see this as a major obstacle to a future in which hydrogen fuel replaces oil. To get around it, they built a device that uses a single pulse of power to split water, so continuous energy is not needed.

Catch and release

The device zaps water with electricity to release oxygen, then a silicon-based chemical mediator dissolved in the water mops up stray protons and electrons. When it is full, the mediator turns blue, letting a human operator know it can be removed and stored for later. When the hydrogen is needed, putting the mediator in contact with a platinum catalyst allows those electrons and protons to recombine to make hydrogen gas.

The whole process uses a single whack of power, and patchy renewable energy will suffice for this, says Cronin. In return, he says, 30 times as much hydrogen can be made than from existing systems. The device could find uses generating power in developing countries or for making fuel on Mars to power a rocket back to Earth.

It is unclear whether Cronin's device will be able to compete with other existing processes, says Steve Reece, a water-splitting expert at Lockheed Martin in Cambridge, Massachusetts. "It will be interesting to see how this concept scales."