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Title: Spatial Configurations of Ti- and Ni- Species Catalyzing Complex Metal Hydrides: X-Ray Absorption Studies and First-Principles DFT and MD Calculations

Abstract

We have performed Ti K-edge EXAFS and XANES measurements on 4 and 3 wt% TiCl3-activated NaAlH4 and (LiBH4+0.5MgH2) and Ni K-edge measurements on 3 and 11 wt% NiCl2-activated (LiBH4+0.5MgH2) and (Li3BN2H8) - prospective hydrogen storage materials. The valence of Ti and Ni is close to zero and invariant during hydrogen cycling. None of the metals enter substitutionally or interstitially into the crystalline lattice of the initial or final products. For the Ti- activated NaAlH4 and (LiBH4+0.5MgH2), amorphous TiAl3 and TiB2 alloys are formed, which are almost invariant during cycling. The Ni doped (LiBH4+0.5MgH2) initially forms amorphous Ni3B, which is partly converted to amorphous Mg2NiHy upon hydrogen loading. Local structure around Ti(Ni) atoms is expressed in terms of a cluster expansion and the interatomic distances, coordination numbers and Debye-Waller factors are determined for competitive structural models. For Ti-activated NaAlH4 the models are elaborated by Ti K-edge XANES, which are interpreted in terms of single-electron multiple scattering calculations. Structural properties and phase stability of hypothetical hydrogenated TiAl3 as well as several products of the decomposition reaction are determined from density functional theory calculation. First-principles molecular dynamics simulations of surface diffusion and chemical reactivity imply that the formation of a few monolayers ofmore » TiAl3 on the surface may be responsible for the significant increase in the reaction rate.« less

Authors:
 [1];  [2];  [3];  [4]; ;  [5]; ;  [6];  [7]
  1. Center for Biophysics at the NSLS, Case Western Reserve Univ., Brookhaven Natl. Lab, Upton, NY 11973 (United States)
  2. (United States)
  3. Department of Energy, Science, and Technology, Brookhaven Natl. Lab, Upton, NY 11973 (United States)
  4. Department of Chemistry, Brookhaven Natl. Lab, Upton, NY 11973 (United States)
  5. HRL Laboratories, LLC, Malibu, CA 90265 (United States)
  6. Materials and Processes Lab, General Motors Research and Development Center, Warren, MI 48090 (United States)
  7. Department of Physics, New Jersey Inst. of Tech., Newark, NJ 07102 (United States)
Publication Date:
OSTI Identifier:
21054704
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 882; Journal Issue: 1; Conference: XAFS13: 13. international conference on X-ray absorption fine structure, Stanford, CA (United States), 9-14 Jul 2006; Other Information: DOI: 10.1063/1.2644617; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ABSORPTION SPECTROSCOPY; CLUSTER EXPANSION; DEBYE-WALLER FACTOR; DENSITY FUNCTIONAL METHOD; DIFFUSION; DOPED MATERIALS; ELECTRONS; FINE STRUCTURE; HYDRIDES; HYDROGEN; HYDROGEN STORAGE; INTERATOMIC DISTANCES; MOLECULAR DYNAMICS METHOD; MULTIPLE SCATTERING; NICKEL ALLOYS; PHASE STABILITY; STRUCTURAL MODELS; TITANIUM ALLOYS; TITANIUM BORIDES; X-RAY SPECTROSCOPY

Citation Formats

Ignatov, A. Yu., Department of Physics, New Jersey Inst. of Tech., Newark, NJ 07102, Graetz, J., Chaudhuri, S., Salguero, T. T., Vajo, J. J., Meyer, M. S., Pinkerton, F. E., and Tyson, T. A. Spatial Configurations of Ti- and Ni- Species Catalyzing Complex Metal Hydrides: X-Ray Absorption Studies and First-Principles DFT and MD Calculations. United States: N. p., 2007. Web. doi:10.1063/1.2644617.
Ignatov, A. Yu., Department of Physics, New Jersey Inst. of Tech., Newark, NJ 07102, Graetz, J., Chaudhuri, S., Salguero, T. T., Vajo, J. J., Meyer, M. S., Pinkerton, F. E., & Tyson, T. A. Spatial Configurations of Ti- and Ni- Species Catalyzing Complex Metal Hydrides: X-Ray Absorption Studies and First-Principles DFT and MD Calculations. United States. doi:10.1063/1.2644617.
Ignatov, A. Yu., Department of Physics, New Jersey Inst. of Tech., Newark, NJ 07102, Graetz, J., Chaudhuri, S., Salguero, T. T., Vajo, J. J., Meyer, M. S., Pinkerton, F. E., and Tyson, T. A. Fri . "Spatial Configurations of Ti- and Ni- Species Catalyzing Complex Metal Hydrides: X-Ray Absorption Studies and First-Principles DFT and MD Calculations". United States. doi:10.1063/1.2644617.
@article{osti_21054704,
title = {Spatial Configurations of Ti- and Ni- Species Catalyzing Complex Metal Hydrides: X-Ray Absorption Studies and First-Principles DFT and MD Calculations},
author = {Ignatov, A. Yu. and Department of Physics, New Jersey Inst. of Tech., Newark, NJ 07102 and Graetz, J. and Chaudhuri, S. and Salguero, T. T. and Vajo, J. J. and Meyer, M. S. and Pinkerton, F. E. and Tyson, T. A.},
abstractNote = {We have performed Ti K-edge EXAFS and XANES measurements on 4 and 3 wt% TiCl3-activated NaAlH4 and (LiBH4+0.5MgH2) and Ni K-edge measurements on 3 and 11 wt% NiCl2-activated (LiBH4+0.5MgH2) and (Li3BN2H8) - prospective hydrogen storage materials. The valence of Ti and Ni is close to zero and invariant during hydrogen cycling. None of the metals enter substitutionally or interstitially into the crystalline lattice of the initial or final products. For the Ti- activated NaAlH4 and (LiBH4+0.5MgH2), amorphous TiAl3 and TiB2 alloys are formed, which are almost invariant during cycling. The Ni doped (LiBH4+0.5MgH2) initially forms amorphous Ni3B, which is partly converted to amorphous Mg2NiHy upon hydrogen loading. Local structure around Ti(Ni) atoms is expressed in terms of a cluster expansion and the interatomic distances, coordination numbers and Debye-Waller factors are determined for competitive structural models. For Ti-activated NaAlH4 the models are elaborated by Ti K-edge XANES, which are interpreted in terms of single-electron multiple scattering calculations. Structural properties and phase stability of hypothetical hydrogenated TiAl3 as well as several products of the decomposition reaction are determined from density functional theory calculation. First-principles molecular dynamics simulations of surface diffusion and chemical reactivity imply that the formation of a few monolayers of TiAl3 on the surface may be responsible for the significant increase in the reaction rate.},
doi = {10.1063/1.2644617},
journal = {AIP Conference Proceedings},
number = 1,
volume = 882,
place = {United States},
year = {Fri Feb 02 00:00:00 EST 2007},
month = {Fri Feb 02 00:00:00 EST 2007}
}