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Abstract:
The catalytic influence of Ni, Zr2Ni5, and LaNi5 on the dehydrogenation properties of milled MgH2, was investigated. MgH2 milled in the presence of Ni (5wt%) and Zr2Ni5 (5wt%) catalysts for 2 h showed apparent activation energies, EA, of 81 and 79 kJ/mol, respectively, corresponding to approximately 50% decrease in EA and a moderate decrease ( approximately 100 deg C) in the decomposition temperature (T dec). A further 27 deg C decrease in Tdec was observed after milling with 10 wt% Ni. Based on the E(A) values, the catalytic activity decreased in the following order: Ni Zr2Ni5 LaNi5. X-ray photoelectron spectroscopy analysis of the milled and dehydrogenated states of the hydrides modified with Ni catalyst revealed that the observed reduction in E(A) may be due to the ability of Ni catalyst to decrease the amount of oxygen atoms in defective positions that are capable of blocking catalytically active sites thereby enhancing the dehydrogenation kinetics. In particular, our results reveal a strong correlation between the type of oxygen species absorbed on Ni-modified MgH2 and E(A) of the dehydrogenation reaction.
| Limitations: |
 APPROVED FOR PUBLIC RELEASE |
| Description: |
Journal article preprint |
| Pages: |
13 |
| Report Date: |
Dec 2011 |
| Report Number: |
A771455 |
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