In-Situ and Real-time Monitoring of Mechanochemical Preparation of Li2Mg(NH2BH3)(4) and Na2Mg(NH2BH3)(4) and Their Thermal Dehydrogenation
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Milošević, Sanja S.
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For the first time, in situ monitoring of uninterrupted mechanochemical synthesis of two bimetallic amidoboranes, M2Mg(NH2BH3)(4) (M=Li, Na), by means of Raman spectroscopy, has been applied. This approach allowed real-time observation of key intermediate phases, and a straightforward follow-up of the reaction course. Detailed analysis of time-dependent spectra revealed a two-step mechanism through MNH2BH3 center dot NH3BH3 adducts as key intermediate phases which further reacted with MgH2, giving M2Mg(NH2BH3)(4) as final products. The intermediates partially take a competitive pathway toward the oligomeric M(BH3NH2BH2NH2BH3) phases. The crystal structure of the novel bimetallic amidoborane Li2Mg(NH2BH3)(4) was solved from high-resolution powder diffraction data and showed an analogous metal coordination to Na2Mg(NH2BH3)(4), but a significantly different crystal packing. Li2Mg(NH2BH3)(4) thermally dehydrogenates releasing highly pure H-2 in the amount of 7 wt.%, and at a lower temperat...ure then its sodium analogue, making it significantly more viable for practical applications.
Keywords:amidoboranes / hydrogen storage / mechanochemistry / Raman spectroscopy / thermal dehydrogenation
Source:Chemistry. A European Journal, 2017, 23, 64, 16274-16282
- Synthesis, processing and characterization of nanostructured materials for application in the field of energy, mechanical engineering, environmental protection and biomedicine (RS-45012)
- Ministry of Environment and Energy, Ministry of Science and Education, Environmental Protection and Energy Efficiency Fund, Croatian Science Foundation under the project New Materials for Energy Storage