2013-05-20 09:06:39 1295 Schouwink, Pascal D'Anna, Vincenza Ley, Morten Brix Lawson Daku, Latévi Max Richter, Bo Jensen, Torben R. Hagemann, Hans Cerný, Radovan The Journal of Physical Chemistry C The J. Phys. Chem. C 1932-7447 2012 116 20 10829 10840 HA http://pubs.acs.org/doi/abs/10.1021/jp212318s http://pubs.acs.org/doi/full/10.1021/jp212318s http://pubs.acs.org/doi/pdf/10.1021/jp212318s Four novel bimetallic borohydrides have been discovered, K₂M(BH₄)₄ (M = Mg or Mn), K₃Mg(BH₄)₅, and KMn(BH₄)₃, and are carefully investigated structurally as well as regarding their decomposition reaction mechanism by means of in situ synchrotron radiation powder X-ray diffraction (SR-PXD), vibrational spectroscopies (Raman and IR), thermal analysis (TGA and DTA), and ab initio density functional theory (DFT) calculations. Mechano-chemical synthesis (ball-milling) using the reactants KBH₄, α-Mg(BH₄)₂, and α-Mn(BH₄)₂ ensures chlorine-free reaction products. A detailed structural analysis reveals significant similarities as well as surprising differences among the two isomorphs K₂M(BH₄)₄, most importantly concerning the extent to which the complex anion [M(BH₄)₄]^2– is isolated in the structure. Anisotropic thermal expansion and an increase in symmetry at high temperatures in K₃Mg(BH₄)₅ is ascribed to the motion of BH₄ groups inducing hydrogen repulsive effects, and the dynamics of K₃Mg(BH₄)₅ are investigated. Decomposition in the manganese system proceeds via the formation of KMn(BH₄)₃, the first perovkite type borohydride reported to date.

]]> H250I500JP442 10.1021/jp212318s 21580 http://www.unige.ch/sciences/chifi/publis/pics/double/ref01295.png http://www.unige.ch/sciences/chifi/publis/refs_pdf/ref01295.pdf 1047 Lindemann, Inge Ferrer, Roger Domènech Dunsch, Lothar Filinchuk, Yaroslav Cerný, Radovan Hagemann, Hans D'Anna, Vincenza Lawson Daku, Latévi Max Schultz, Ludwig Gutfleisch, Oliver Chemistry - A European Journal Chem. - Eur. J. 0947-6539 2010 16 8707 8712 HA borohydrides; density functional calculations; hydrogen storage; metathesis; X-ray diffraction borohydrides density functional calculations hydrogen storage metathesis X-ray diffraction http://www3.interscience.wiley.com/cgi-bin/fulltext/123563128/PDFSTART The new double-cation Al-Li-borohydride is an attractive candidate material for hydrogen storage due to a very low hydrogen desorption temperature (~70 °C) combined with a high hydrogen density (17.2 wt %). It was synthesised by high-energy ball milling of AlCl₃ and LiBH₄. The structure of the compound was determined from image-plate synchrotron powder diffraction supported by DFT calculations. The material shows a unique 3D framework structure within the borohydrides (space group=P-43n, a=11.3640(3) Å). The unexpected composition Al₃Li₄(BH₄)₁₃ can be rationalized on the basis of a complex cation [(BH₄)Li₄]³⁺ and a complex anion [Al(BH₄)₄]^-. The refinements from synchrotron powder diffraction of different samples revealed the presence of limited amounts of chloride ions replacing the borohydride on one site. In situ Raman spectroscopy, differential scanning calorimetry (DSC), thermogravimetry (TG) and thermal desorption measurements were used to study the decomposition pathway of the compound. Al-Li-borohydride decomposes at ~70 °C, forming LiBH₄. The high mass loss of about 20 % during the decomposition indicates the release of not only hydrogen but also diborane.

]]> H199I398P386 10.1002/chem.201000831 14778 http://www.unige.ch/sciences/chifi/publis/pics/double/ref01047.png http://www.unige.ch/sciences/chifi/publis/refs_pdf/ref01047.pdf