Understanding the Role of Ti in Reversible Hydrogen Storage as Sodium Alanate: A Combined Experimental and Density Functional Theoretical Approach.
We report the results of an experimental and theoretical study of hydrogen storage in sodium alanate (NaAIH). Reversible hydrogen storage in this material is dependent on the presence of 2-4% Ti dopant. Our combined study shows that the role of Ti may be linked entirely to Ti-containing active catal...
| Publicado en: | Journal of the American Chemical Society Vol. 128; no. 35; pp. 11404 - 11416 |
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| Autores principales: | , , , , |
| Formato: | Artículo |
| Publicado: |
American Chemical Society
9/6/2006
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| Materias: | |
| Acceso en línea: | Ver este registro en EBSCOhost |
| fields | @attributes: recordID: 1 pdfLink: plink: https://search.ebscohost.com/login.aspx?direct=true&db=hlh&AN=22312693&site=ehost-live header: @attributes: shortDbName: hlh uiTerm: 22312693 longDbName: Humanities International Complete uiTag: AN controlInfo: bkinfo: jinfo: jid: 00027863 ACS jtl: Journal of the American Chemical Society issn: 00027863 maglogo: N pubinfo: dt: 9/6/2006 vid: 128 iid: 35 pid: 997 pub: American Chemical Society artinfo: ui: 22312693 10.1021/ja060437s ppf: 11404 ppct: 12 formats: tig: atl: Understanding the Role of Ti in Reversible Hydrogen Storage as Sodium Alanate: A Combined Experimental and Density Functional Theoretical Approach. aug: au: Chaudhuri, Santanu Graetz, Jason Ignatov, Alex Reilly, James J. Muckerman, James T. affil: Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973-5000 Department of Energy, Science and Technology, Brookhaven National Laboratory, Upton, New York 11973 National Synchrotron Light Source, Brookhaven National Laboratory, Upton, New York 11973 su: Hydrogenation Sodium compounds Density functionals Solution (Chemistry) Chemical reactions Chemistry sug: subj: Hydrogenation Sodium compounds Density functionals Solution (Chemistry) Chemical reactions Chemistry ab: We report the results of an experimental and theoretical study of hydrogen storage in sodium alanate (NaAIH). Reversible hydrogen storage in this material is dependent on the presence of 2-4% Ti dopant. Our combined study shows that the role of Ti may be linked entirely to Ti-containing active catalytic sites in the metallic AI phase present in the dehydrogenated NaAIH4. The EXAFS data presented here show that dehydrogenated samples contain a highly disordered distribution of Ti-AI distances with no long-range order beyond the second coordination sphere. We have used density functional theory techniques to calculate the chemical potential of possible Ti arrangements on an AI(001) surface for Ti coverages ranging from 0.125 to 0.5 monolayer (ML) and have identified those that can chemisorb molecular hydrogen via spontaneous or only moderately activated pathways. The chemisorption process exhibits a characteristic nodal symmetry property for the low-barrier sites: the incipient doped surface-H adduct's highest occupied molecular orbital (HOMO) incorporates the σ* antibonding molecular orbital of hydrogen, allowing the transfer of charge density from the surface to dissociate the molecular hydrogen. This work also proposes a plausible mechanism for the transport of an aluminum hydride species back into the Nail lattice that is supported by Car-Parrinello molecular dynamics (CPMD) simulations of the stability and mobility of aluminum clusters (alanes) on AI(001). As an experimental validation of the proposed role of titanium and the subsequent diffusion of alanes, we demonstrate experimentally that AIH reacts with Nail to form NaAIH without any requirement of a catalyst or hydrogen overpressure. pubtype: Academic Journal doctype: Article src: R language: English refInfo: copyright: @attributes: flag: Y dt: @attributes: year: 2006 holdings: @attributes: islocal: N |
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