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Ultrafast Bulk Diffusion of AlHx in High-Entropy Dehydrogenation Intermediates of NaAlH4

TitleUltrafast Bulk Diffusion of AlHx in High-Entropy Dehydrogenation Intermediates of NaAlH4
Publication TypeJournal Article
Year of Publication2014
AuthorsZhang, F, Wood, BC, Wang, Y, Wang, CZ, Ho, KM, Chou, MY
JournalJournal of Physical Chemistry C
Date Published08
Type of ArticleArticle
ISBN Number1932-7447
Accession NumberWOS:000340444500009
Keywordsaluminum hydrides, calculations, density-functional theory, elastic, generalized gradient approximation, neutron-scattering, point-defect dynamics, reversible hydrogen storage, sodium alanate, ti-doped naalh4, total-energy, wave basis-set

0.1 eV, and we directly observe the predicted diffusive pathways in FPMD simulations at picosecond time scales. In contrast, such diffusion in the alpha phase is inaccessible to FPMD, consistent with much higher barriers. The transport behavior of gamma-NaAlH4, in addition to key dynamical and structural signatures, is consistent with experimental observations of high-mobility species, strongly supporting the idea that an intermediate transition from the alpha phase to a high-entropy polymorph facilitates the hydrogen-releasing decomposition of NaAlH4. Our results provide an answer to longstanding questions regarding the responsible agent for the experimentally observed efficient Al transport during dehydrogenation and suggest that mass transport and phase transformation kinetics are coupled. Implications for understanding the (de)hydrogenation of undoped and catalyzed NaAlH4 are discussed.

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