Hydrogen dynamics in Na3AlH6: A combined density functional theory and quasielastic neutron scattering study

Johannes Voss, Qing Shi, Hjalte Sylvest Jacobsen, M. Zamponi, Kim Lefmann, Tejs Vegge

    Research output: Contribution to journalJournal articleResearchpeer-review

    Abstract

    Understanding the elusive catalytic role of titanium-based additives on the reversible hydrogenation of complex hydrides is an essential step toward developing hydrogen storage materials for the transport sector. Improved bulk diffusion of hydrogen is one of the proposed effects of doping sodium alanate with TiCl3, and here we study hydrogen dynamics in doped and undoped Na3AlH6 using a combination of density functional theory calculations and quasielastic neutron scattering. The hydrogen dynamics is found to be vacancy mediated and dominated by localized jump events, whereas long-range bulk diffusion requires significant activation. The fraction of mobile hydrogen is found to be small for both undoped and doped Na3AlH6, even at 350 K, and improved hydrogen diffusion as a result of bulk-substituted titanium is found to be unlikely. We also propose that previously detected low-temperature point defect motion in sodium alanate could result from vacancy-mediated sodium diffusion.
    Original languageEnglish
    JournalJournal of Physical Chemistry Part B: Condensed Matter, Materials, Surfaces, Interfaces & Biophysical
    Volume111
    Issue number15
    Pages (from-to)3886-3892
    ISSN1520-6106
    DOIs
    Publication statusPublished - 2007

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