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Characterization of titanium dopants in sodium alanate by electron paramagnetic resonance spectroscopy

Published online by Cambridge University Press:  01 December 2005

Meredith T. Kuba ,
Sandra S. Eaton ,
Christine Morales  and
Craig M. Jensen
Meredith T. Kuba
Affiliation:
Department of Chemistry, University of Hawaii, Honolulu, Hawaii 96822
Sandra S. Eaton
Affiliation:
Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado 80208
Christine Morales
Affiliation:
Department of Chemistry, University of Hawaii, Honolulu, Hawaii 96822
Craig M. Jensen*
Affiliation:
Department of Chemistry, University of Hawaii, Honolulu, Hawaii 96822
*
a) Address all correspondence to this author. e-mail: jensen@gold.chem.hawaii.edu
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Abstract

Electron paramagnetic resonance (EPR) spectra were obtained for samples of Ti-doped NaAlH4 subjected to different numbers of cycles of dehydrogenation/re-hydrogenation. Ti is observed to evolve from its initial Ti(III) state through a series of Ti(0) species during the first 5 cycles. Although the conversion of Ti(III) to Ti(0) occurs much more readily for TiCl3-doped samples than those prepared with TiF3, in both cases the evolution of Ti follows the same sequence that involves 3 distinguishable Ti(0) species and ends in the predominance of the same single Ti(0) species. The spectrum of a sample of NaAlH4 containing 2 mol% of cubic Al3Ti is distinctly different than any of those observed for the Ti(0) species that arise during the hydrogen cycling of the hydride. The major changes in the nature of the predominant Ti species have little if any effect on the dehydrogenation kinetics, which strongly suggests that the profoundly enhanced hydrogen cycling kinetics of Ti-doped NaAlH4 are due to a Ti species present in only a relatively minor amount.

Keywords

Energy-storageMagnetic properties
Type
Articles—Energy and The Environment Special Section
Information
Journal of Materials Research , Volume 20 , Issue 12 , December 2005 , pp. 3265 - 3269
Copyright
Copyright © Materials Research Society 2005

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