Synthesis and thermal decomposition of potassium tetraamidoboranealuminate, K[Al(NH2BH3)4]

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A new potassium tetraamidoboranealuminate, K[Al(NH2BH3)4], has been synthesized by a mechanochemical reaction between KAlH4 and NH3BH3. The compound, K[Al(NH2BH3)4], crystallizes in a triclinic unit cell with space group symmetry P-1. The crystal structure consists of [K(NH2BH3)6]5 - octahedra which facilitate the bridging between K+ in 1D chains, while also bridging K+ to Al3+ to connect the 1D chains in a 3D network. Thermal analysis reveals that K[Al(NH2BH3)4] decomposes in two exothermic steps at T ~ 94 and 138 °C and releases primarily hydrogen. The total gas release amounts to ~6.0 wt% H2. The decomposition products are investigated ex situ by powder X-ray diffraction, infrared spectroscopy, and 11B and 27Al NMR and identified as KBH4 and amorphous phases, possibly BN3, N2BH, and/or NBH2 whereas aluminum is found in four-, five-, and six-fold coordination. Unfortunately, the decomposed sample shows no hydrogen absorption at T = 260 °C and p(H2) = 110 bar.

Original languageEnglish
JournalInternational Journal of Hydrogen Energy
Volume43
Issue1
Pages (from-to)311-321
Number of pages11
ISSN0360-3199
DOIs
Publication statusPublished - 1 Jan 2018

    Research areas

  • Ammonia borane, Hydrogen storage, Metal amidoboranes, Potassium alanate, Potassium tetraamidoboranealuminate

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