Hydrogenation properties of lithium and sodium hydride- closo -borate, [B10H10]2- and [B12H12]2-, composites

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  • Steffen R.H. Jensen
  • ,
  • Mark Paskevicius
  • ,
  • Bjarne R.S. Hansen
  • ,
  • Anders S. Jakobsen
  • ,
  • Kasper T. Møller
  • ,
  • James L. White, Sandia National Laboratories, California
  • ,
  • Mark D. Allendorf, Sandia National Laboratories, California
  • ,
  • Vitalie Stavila, Sandia National Laboratories, California
  • ,
  • Jørgen Skibsted
  • Torben R. Jensen

The hydrogen absorption properties of metal closo-borate/metal hydride composites, M2B10H10-8MH and M2B12H12-10MH, M = Li or Na, are studied under high hydrogen pressures to understand the formation mechanism of metal borohydrides. The hydrogen storage properties of the composites have been investigated by in situ synchrotron radiation powder X-ray diffraction at p(H2) = 400 bar and by ex situ hydrogen absorption measurements at p(H2) = 526 to 998 bar. The in situ experiments reveal the formation of crystalline intermediates before metal borohydrides (MBH4) are formed. On the contrary, the M2B12H12-10MH (M = Li and Na) systems show no formation of the metal borohydride at T = 400 °C and p(H2) = 537 to 970 bar. 11B MAS NMR of the M2B10H10-8MH composites reveal that the molar ratio of LiBH4 or NaBH4 and the remaining B species is 1:0.63 and 1:0.21, respectively. Solution and solid-state 11B NMR spectra reveal new intermediates with a B:H ratio close to 1:1. Our results indicate that the M2B10H10 (M = Li, Na) salts display a higher reactivity towards hydrogen in the presence of metal hydrides compared to the corresponding [B12H12]2- composites, which represents an important step towards understanding the factors that determine the stability and reversibility of high hydrogen capacity metal borohydrides for hydrogen storage.

Original languageEnglish
JournalPhysical Chemistry Chemical Physics
Volume20
Issue23
Pages (from-to)16266-16275
Number of pages10
ISSN1463-9076
DOIs
Publication statusPublished - 1 Jan 2018

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