Characterization of a new phase of ammonia borane

Wendy J. Shaw, Mark Bowden, Abhi Karkamkar, Christopher J. Howard, David J. Heldebrant, Nancy J. Hess, John C. Linehan, Tom Autrey

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45 Citations (Scopus)

Abstract

An uncharacterized phase of ammonia borane (AB) was previously identified while investigating the thermal aging of this hydrogen rich solid state material. This phase was identified as a key intermediate for the release of hydrogen from AB prompting the current characterization study. The new phase (AB*) was investigated extensively using in situ solid state MAS NMR spectroscopy, including 11B, 15N and 1H NMR. Single-pulse excitation, cross polarization and T1 relaxation experiments for all nuclei collectively demonstrated a significant increase in mobility of AB in the new phase compared to the room temperature phase of AB, consistent with a highly mobile solid. This implies a disruption of the extensive dihydrogen bonding network, allowing increased motional freedom. Complementary studies by in situ X-ray diffraction showed AB* to have the same crystal lattice as AB, but suggested an expanded lattice, providing support for increased mobility. NMR measurements of AB embedded into a mesoporous scaffold were also consistent with high mobility in AB*. These data suggest that a breakdown of the extensive hydrogen bonding network occurs before hydrogen can be released and will be an important factor in the practical use of AB as a hydrogen storage material.

Original languageEnglish
Pages (from-to)796-804
Number of pages9
JournalEnergy and Environmental Science
Volume3
Issue number6
DOIs
Publication statusPublished - Jun 11 2010

ASJC Scopus subject areas

  • Environmental Chemistry
  • Renewable Energy, Sustainability and the Environment
  • Nuclear Energy and Engineering
  • Pollution

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    Shaw, W. J., Bowden, M., Karkamkar, A., Howard, C. J., Heldebrant, D. J., Hess, N. J., Linehan, J. C., & Autrey, T. (2010). Characterization of a new phase of ammonia borane. Energy and Environmental Science, 3(6), 796-804. https://doi.org/10.1039/b914338f