Jesse Emspak, contributor
A fuel cell-powered car at the International Hydrogen & Fuel Cell Expo 2010 (Image: Junko Kimura/Getty)
Hydrogen fuel cells for cars are still wildly expensive, mainly because they have to use costly noble metals such as platinum. Now researchers have demonstrated that aluminium can be treated to store and release hydrogen - making it far cheaper than existing methods.
There have been several attempts at a cheaper alternative, involving materials such as carbon nanotubes and organic crystals. Storing hydrogen and separating it from other substances for use presents other problems - hydrogen either has to be very cold (on the order of -250 °C) or pressurised.
Irinder S. Chopra, a physics PhD student at the University of Texas, Dallas, led a team that tried depositing a tiny bit of titanium on pure aluminium, resulting in an arrangement of aluminium atoms broken up by the occasional titanium atom in a regular pattern.
When the doped aluminium is exposed to molecular hydrogen at 90 degrees kelvin (-183 °C), the H2 breaks up and binds to the metal forming a hydride. When the metal is heated, the hydrogen is released and makes H2 again. Doped aluminium can store up to 10 per cent of its weight in hydrogen - much better than other options, says Yves Chabal, a professor of materials science and one of the co-authors.
There are still challenges. How much contamination the doped aluminium can be exposed to before it won't bind to the hydrogen anymore is one. How dense the hydrogen can be - the initial experiments were done in near vacuum conditions - is another. That said, a fuel cell using aluminium would use a widely available and recycled metal (and give one more reason to bring the cans back).
Journal reference: Nature Materials DOI: 10.1038/nmat3123