Better storage

at the National Institute of Standards and Technology (nist) in the us have created a new material that can store up to 10 per cent of its weight in hydrogen, taking hydrogen fuel cells closer to reality. Automobiles run on hydrogen is one of the potential applications of emerging fuel cell technology.

It's known that some crystalline materials made of certain metal and oxygen clusters connected through organic compounds can store hydrogen molecules. In such materials, hydrogen latches onto the metal-organic framework (mof) (see picture).

But the zinc-based nanoporous material designed by Taner Yildirim and Michael Hartman, termed mof5, has a network of "nano-cages', in addition to four types of hydrogen docking sites, commonly-found in other similar materials. The study appeared in Physical Review Letters (Vol 95, No 21, November 16, 2005).

The finding suggests mof materials could be engineered to optimise hydrogen storage and release under normal vehicle-operating conditions. Researchers working on an ambitious hydrogen car project in the us have set a lower limit of six per cent capacity for economically viable hydrogen storage. The nist effort meets this requirement.

"The molecules are packed in a fashion similar to the way apples or oranges fill a bowl,' Yildirim explains in a release put out by nist. The unexpected nano-cages introduce the potential for spillover capacity, he says.

Currently, hydrogen storage levels of 10 per cent can be achieved but at impractically low temperatures.