Author's School

Graduate School of Arts & Sciences

Author's Department/Program

Physics

Language

English (en)

Date of Award

January 2010

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Chair and Committee

Mark Conradi

Abstract

NaAlH4 has become the archetypal complex: ionic-covalent) hydrogen storage solid, since the discovery in 1997 that titanium and some other metals catalyze the reaction in both directions. Given that spatially separated NaH and Al under excess H2 pressure can form NaAlH4, we have hypothesized a mobile Al- or Na- bearing intermediate species in the reaction scheme. 27Al in situ NMR has been used to discover such a new species during dehydriding of NaAlH4. Importantly, the new species can also be formed under excess H2 pressure without net evolution of Al and H2; the new species can be returned to ambient for further study. The features of the new species include: a very rapid 27Al T1, a sharp line: without MAS) at 300 K that broadens by -60oC, an accompanying sharp hydrogen NMR line that is also motionally narrowed, CPMAS evidence of bonded or at least nearby H, and a 27Al shift just above NaAlH4. The new species appears to be a highly defective form of NaAlH4, where the large concentration of vacancies promotes rapid diffusion of Al and H.

DOI

https://doi.org/10.7936/K7W37TFR

Comments

Permanent URL: http://dx.doi.org/10.7936/K7W37TFR

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