Reversible vacancy formation and recovery during dehydrogenation- hydrogenation cycling of Ti-doped NaAlH4

Kouji Sakaki; Yumiko Nakamura; Etsuo Akiba; Meredith T. Kuba; Craig M. Jensen

doi:10.1021/jp100810u

Reversible vacancy formation and recovery during dehydrogenation- hydrogenation cycling of Ti-doped NaAlH₄

Kouji Sakaki, Yumiko Nakamura, Etsuo Akiba, Meredith T. Kuba, Craig M. Jensen

Research output: Contribution to journal › Article › peer-review

19 Citations (Scopus)

Abstract

The mechanism of the dehydrogenation-rehydrogenation of Ti-doped NaAlH ₄ was investigated through X-ray diffraction (XRD) studies and Doppler broadening measurements of positron annihilation. Phase transformations during dehydrogenation and hydrogenation half-cycles were studied by the Rietveld analysis of XRD profiles. Changes in lattice defects were monitored by determination of the S parameter of the Doppler broadening spectra, which shows the ratio of positron annihilation to valence electrons. No significant changes in lattice parameters and the S parameter were observed directly following Ti doping. However, the S parameter increased upon dehydrogenation and decreased following rehydrogenation. These results indicate that vacancies are not introduced into NaAlH₄ upon Ti doping, but rather, they arise during dehydrogenation and disappear during rehydrogenation.

Original language	English
Pages (from-to)	6869-6873
Number of pages	5
Journal	Journal of Physical Chemistry C
Volume	114
Issue number	14
DOIs	https://doi.org/10.1021/jp100810u
Publication status	Published - Apr 15 2010
Externally published	Yes

All Science Journal Classification (ASJC) codes

Electronic, Optical and Magnetic Materials
Energy(all)
Physical and Theoretical Chemistry
Surfaces, Coatings and Films

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title = "Reversible vacancy formation and recovery during dehydrogenation- hydrogenation cycling of Ti-doped NaAlH4",

abstract = "The mechanism of the dehydrogenation-rehydrogenation of Ti-doped NaAlH 4 was investigated through X-ray diffraction (XRD) studies and Doppler broadening measurements of positron annihilation. Phase transformations during dehydrogenation and hydrogenation half-cycles were studied by the Rietveld analysis of XRD profiles. Changes in lattice defects were monitored by determination of the S parameter of the Doppler broadening spectra, which shows the ratio of positron annihilation to valence electrons. No significant changes in lattice parameters and the S parameter were observed directly following Ti doping. However, the S parameter increased upon dehydrogenation and decreased following rehydrogenation. These results indicate that vacancies are not introduced into NaAlH4 upon Ti doping, but rather, they arise during dehydrogenation and disappear during rehydrogenation.",

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T1 - Reversible vacancy formation and recovery during dehydrogenation- hydrogenation cycling of Ti-doped NaAlH4

AU - Sakaki, Kouji

AU - Nakamura, Yumiko

AU - Akiba, Etsuo

AU - Kuba, Meredith T.

AU - Jensen, Craig M.

PY - 2010/4/15

Y1 - 2010/4/15

N2 - The mechanism of the dehydrogenation-rehydrogenation of Ti-doped NaAlH 4 was investigated through X-ray diffraction (XRD) studies and Doppler broadening measurements of positron annihilation. Phase transformations during dehydrogenation and hydrogenation half-cycles were studied by the Rietveld analysis of XRD profiles. Changes in lattice defects were monitored by determination of the S parameter of the Doppler broadening spectra, which shows the ratio of positron annihilation to valence electrons. No significant changes in lattice parameters and the S parameter were observed directly following Ti doping. However, the S parameter increased upon dehydrogenation and decreased following rehydrogenation. These results indicate that vacancies are not introduced into NaAlH4 upon Ti doping, but rather, they arise during dehydrogenation and disappear during rehydrogenation.

AB - The mechanism of the dehydrogenation-rehydrogenation of Ti-doped NaAlH 4 was investigated through X-ray diffraction (XRD) studies and Doppler broadening measurements of positron annihilation. Phase transformations during dehydrogenation and hydrogenation half-cycles were studied by the Rietveld analysis of XRD profiles. Changes in lattice defects were monitored by determination of the S parameter of the Doppler broadening spectra, which shows the ratio of positron annihilation to valence electrons. No significant changes in lattice parameters and the S parameter were observed directly following Ti doping. However, the S parameter increased upon dehydrogenation and decreased following rehydrogenation. These results indicate that vacancies are not introduced into NaAlH4 upon Ti doping, but rather, they arise during dehydrogenation and disappear during rehydrogenation.

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Reversible vacancy formation and recovery during dehydrogenation- hydrogenation cycling of Ti-doped NaAlH₄

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