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Characterization of the Local Titanium Environment in Doped Sodium Aluminum Hydride using X-ray Absorption Spectroscopy

Published online by Cambridge University Press:  01 February 2011

J. Graetz ,
A.Yu. Ignatov ,
T.A. Tyson ,
J.J. Reilly  and
J. Johnson
J. Graetz
Affiliation:
Department of Energy Sciences and Technology, Brookhaven National Laboratory, Upton, New York 11973
A.Yu. Ignatov
Affiliation:
Department of Physics, New Jersey Institute of Technology, Newark, New Jersey 07102
T.A. Tyson
Affiliation:
Department of Physics, New Jersey Institute of Technology, Newark, New Jersey 07102
J.J. Reilly
Affiliation:
Department of Energy Sciences and Technology, Brookhaven National Laboratory, Upton, New York 11973
J. Johnson
Affiliation:
Department of Energy Sciences and Technology, Brookhaven National Laboratory, Upton, New York 11973
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Abstract

Ti K -edge x-ray absorption spectroscopy was used to explore the local titanium environment and valence in 2–4 mol% Ti-doped sodium alanate. An estimate of the oxidation state of the dopant, based upon known standards, revealed a zero-valent titanium atom. An analysis of the near-edge and extended fine structures indicates that the Ti does not enter substitutional or interstitial sites in the NaAlH4 lattice. Rather, the Ti is located on/near the surface and is coordinated by 10.2±1 aluminum atoms with an interatomic distance of 2.82±0.01 Å, similar to that of TiAl3. The Fourier transformed EXAFS spectra reveal a lack of long-range order around the Ti dopant indicating that the Ti forms nano-clusters of TiAl3. The similarity of the spectra in the hydrided and dehydrided samples suggests that the local Ti environment is nearly invariant during hydrogen cycling.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 837: Symposium N – Materials for Hydrogen Storage – 2004 , 2004 , N2.4
Copyright
Copyright © Materials Research Society 2005

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References

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