New clues about a hydrogen fuel catalyst( RICHLAND Wash. -- To use hydrogen as...)

RICHLAND, Wash. -- To use hydrogen as a clean energy source, some engineers want to pack hydrogen into a larger molecule, rather than compressing the gas into a tank. A gas flows easily out of a tank, but getting hydrogen out of a molecule requires a catalyst. Now, researchers reveal new details about one such catalyst. The results are a step toward designing catalysts for use in hydrogen energy applications such as fuel cells.

Scientists from the Department of Energy's Pacific Northwest National Laboratory combined experimental and theoretical studies to identify the characteristics of the catalyst, a cluster of rhodium, boron and other atoms. The catalyst chemically reacts with ammonia borane, a molecule that stores hydrogen densely, to release the hydrogen as a gas. Their results, which reveal many molecular details of this catalytic reaction, appear August 5 in the Journal of the American Chemical Society.

"These studies tell us what is the hardest part of the chemical reaction," said PNNL chemist and study author Roger Rousseau. "If we can find a way to change the hard part, that is, make it easier to release the hydrogen, then we can improve this catalyst."

Researchers and engineers are trying to create a hydrogen fuel system that stores hydrogen safely and discharges hydrogen easily, which can then be used in fuel cells or other applications.

One way to achieve such a fuel system is by "storing" hydrogen as part of a larger molecule. The molecule that contains hydrogen atoms, in this case ammonia borane, serves as a sort of structural support. The catalyst plucks the hydrogen from the ammonia borane as needed to run the device.

The PNNL chemists in the Institute for Interfacial Catalysis study a rhodium-based catalyst that performs this job fairly well, but might have potential for improvement. Their initial work showed that the catalyst worked as a molecule that co
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