As researchers at Pacific Northwest National Laboratory investigatedthe hydrogen storage capabilities of amineborane compounds, they knew that a rhodium catalyst readily releaseshydrogen from the compound at roomtemperature. But they weren't sure how it worked. Aside from thescientific quest for knowledge, understanding the mechanism at workwith rhodium may help with the development of a more cost-effectivecatalyst to enablehydrogen storage.
PNNL scientists used a type of x-ray spectroscopy available at theAdvanced Photon Source synchrotron at ArgonneNational Laboratory to look at the reaction as it was occurring. Theyfound the active site of the catalystcentered around a cluster of about four rhodium atoms. They also foundthat the catalyst structure during thereaction was different than the structure before and after thereaction, thus highlighting the importance of measuring the catalyststructure during the reaction conditions.
By combining these results with subsequent in situ nuclear magnetic resonance and infrared spectroscopy,researchers were able to "see" what happens to the boron compound as the hydrogen is released. The resultsshow the mechanism of how the amine borane compound binds to the active catalyst and then how the hydrogenmolecule is released as a gas.
The research demonstrates the importance of "operando" methods -or observation of the fundamental molecular level measurements of thecatalyst, the reactants and the products - under practical conditions.The PNNLgroup is using this approach to investigate other chemical reactionswhere little is known about the key catalytic processes.
Pacific Northwest National Laboratory researcher Tom Autrey will present his results at 1:30 p.m., Monday, Aug. 29.
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