Early deuteration steps of Pd- and Ta/Pd- catalyzed Mg70Al30 thin films observed at room temperature
✍ Scribed by Christopher Harrower; Eric Poirier; Helmut Fritzsche; Peter Kalisvaart; Sushil Satija; Bulent Akgun; David Mitlin
- Publisher
- Elsevier Science
- Year
- 2010
- Tongue
- English
- Weight
- 555 KB
- Volume
- 35
- Category
- Article
- ISSN
- 0360-3199
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✦ Synopsis
Deuterium absorption in Mg 70 Al 30 thin films coated with a Pd layer and a Ta/Pd bilayer were investigated using in situ neutron reflectometry at room temperature and deuterium pressures up to 1.3 bar. The approach used provides a detailed profile, at the nanoscale, of the deuterium content inside the specific layers that constitute the films. It is found that Mg 70 Al 30 can store up to 5 wt.% under these mild conditions following a two-step mechanism. The latter involves the deuteration of the top and bottom catalyst layers first, followed by the main Mg 70 Al 30 layer. The presence of deuterium throughout the films in the early absorption stages evidences atomic deuterium spillover from the catalyst layers. The addition of a Ta layer between the Pd and Mg 70 Al 30 was found to allow observable absorption at a pressure 10 times lower than on the Ta-free sample, without affecting the storage capacity. Our measurements imply that this improvement in kinetics is due to a lowering of the nucleation barrier for the formation of the hydride phase in the Mg 70 Al 30 layer.