Mechanistic studies of ammonia borane dehydrogenation

Ahmad Al-Kukhun, Hyun Tae Hwang, Arvind Varma

Research output: Contribution to journalArticlepeer-review

49 Scopus citations

Abstract

Ammonia borane (NH3BH3, AB) has received extensive attention as a potential hydrogen storage medium, however hydrogen release mechanisms from AB are not well understood. AB follows different reaction routes if the dehydrogenation occurs in solvent or solid state, but a comparative study for AB dehydrogenation in these two states is not available. In this work, a detailed study of AB dehydrogenation mechanism in diglyme and solid state is presented, and a comprehensive reaction network for both cases is proposed. The experimental and DFT results suggest that two main reaction pathways occur; one involves cyclization of monomers which results in faster dehydrogenation at lower temperature, while the other involves propagation to acyclic intermediates which requires higher temperature to carry out the cyclization step. AB dehydrogenation in solid state was experimentally found to be initiated by B-N bond cleavage and not by direct dehydrogenation, which agrees with high level CCSD(T)/MP2 calculations reported previously. It was found that diglyme plays a significant role in hindering B-N bond cleavage of AB which facilitates the cyclization pathway. In solid state, experiments including labeled AB (ND 3BH3) mapped out the source of hydrogen (from hydridic or protonic ends), and a clear difference in the degree of dehydrogenation from the two ends is demonstrated.

Original languageEnglish
Pages (from-to)169-179
Number of pages11
JournalInternational Journal of Hydrogen Energy
Volume38
Issue number1
DOIs
StatePublished - Jan 11 2013

Bibliographical note

Funding Information:
We gratefully acknowledge the U.S. Department of Energy for financial support of this research under grant number DOE–FG36–06GO086050 .

Keywords

  • Ammonia borane
  • Density functional theory (DFT)
  • Hydrogen storage
  • NMR spectroscopy
  • Thermolysis

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • Fuel Technology
  • Condensed Matter Physics
  • Energy Engineering and Power Technology

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