Hydrogen storage in sodium aluminum hydride.

Ozolins, Vidvuds ; Herberg, J.L. (Lawrence Livermore National Laboratories, Livermore, CA) ; McCarty, Kevin F. ; Maxwell, Robert S. (Lawrence Livermore National Laboratories, Livermore, CA) ; Stumpf, Roland Rudolph ; Majzoub, Eric H.

Sandia National Laboratories

关键词: Electronic Structure;    Aluminium;    Raman Spectroscopy;    Hydrides;    Sodium;   

DOI  :  10.2172/875967
RP-ID  :  SAND2005-6833
RP-ID  :  AC04-94AL85000
RP-ID  :  875967

美国|英语

来源: UNT Digital Library

【 摘 要 】

Sodium aluminum hydride, NaAlH{sub 4}, has been studied for use as a hydrogen storage material. The effect of Ti, as a few mol. % dopant in the system to increase kinetics of hydrogen sorption, is studied with respect to changes in lattice structure of the crystal. No Ti substitution is found in the crystal lattice. Electronic structure calculations indicate that the NaAlH{sub 4} and Na{sub 3}AlH{sub 6} structures are complex-ionic hydrides with Na{sup +} cations and AlH{sub 4}{sup -} and AlH{sub 6}{sup 3-} anions, respectively. Compound formation studies indicate the primary Ti-compound formed when doping the material at 33 at. % is TiAl{sub 3} , and likely Ti-Al compounds at lower doping rates. A general study of sorption kinetics of NaAlH{sub 4}, when doped with a variety of Ti-halide compounds, indicates a uniform response with the kinetics similar for all dopants. NMR multiple quantum studies of solution-doped samples indicate solvent interaction with the doped alanate. Raman spectroscopy was used to study the lattice dynamics of NaAlH{sub 4}, and illustrated the molecular ionic nature of the lattice as a separation of vibrational modes between the AlH{sub 4}{sup -} anion-modes and lattice-modes. In-situ Raman measurements indicate a stable AlH{sub 4}{sup -} anion that is stable at the melting temperature of NaAlH{sub 4}, indicating that Ti-dopants must affect the Al-H bond strength.