Nano-scale bi-layer Pd/Ta, Pd/Nb, Pd/Ti and Pd/Fe catalysts for hydrogen sorption in magnesium thin films

We analyzed the elevated temperature volumetric hydrogen sorption behavior of magnesium thin films catalyzed by nano-scale bi-layers of Pd/Ta, Pd/Nb, Pd/Ti and Pd/Fe. Sorption of magnesium catalyzed by pure Pd was determined as a baseline. Sorption cycling demonstrated that when utilizing pure Pd an...

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Bibliographic Details
Published in:International journal of hydrogen energy 2009-09, Vol.34 (18), p.7741-7748
Main Authors: Tan, XueHai, Harrower, Christopher T., Amirkhiz, Babak Shalchi, Mitlin, David
Format: Article
Language:English
Subjects:
Catalysis
Catalysts
Hydrogen storage
Magnesium
Nanostructure
Niobium
Palladium
Sorption
Thin films
Titanium
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Summary:We analyzed the elevated temperature volumetric hydrogen sorption behavior of magnesium thin films catalyzed by nano-scale bi-layers of Pd/Ta, Pd/Nb, Pd/Ti and Pd/Fe. Sorption of magnesium catalyzed by pure Pd was determined as a baseline. Sorption cycling demonstrated that when utilizing pure Pd and the Pd/Fe bi-layer catalysts the sorption kinetics of the Mg films rapidly degraded. However with the Pd/Nb, Pd/Ti and Pd/Ta bi-layer catalysts the composite remained cycleable. After multiple sorption cycles the Pd/Nb and Pd/Ti catalyst combinations possessed the fastest kinetics. X-ray diffraction analysis showed that NbH 0.5 and TiH 2 are formed during testing. Basic thermodynamic analysis indicates that NbH 0.5 and TiH 2 should be stable both during absorption and during desorption. We believe that this is why Nb and Ti are the most effective intermediate layers: The elements form stable hydrides at the Mg surfaces preventing complete Pd-Mg interdiffusion and/or acting as hydrogen catalysts and pumps.
ISSN:0360-3199
1879-3487
DOI:10.1016/j.ijhydene.2009.07.026