A hydride composite featuring mutual destabilisation and reversible boron exchange: Ca(BH4)2–Mg2NiH4
N. Bergemann, C. Pistidda, C. Milanese, M. Aramini, S. Huotari, P. Nolis, A. Santoru, M. R. Chierotti, A.-L. Chaudhary, M. D. Baro, T. Klassen and M. Dornheim.
ABSTRACT:The system Ca(BH4)2–Mg2NiH4 is used as a model to prove the unique possibility to fully reverse the borohydride decomposition process even in cases where the decomposition reaction leads to undesired stable boron containing species (boron sinks). The formation of MgNi2.5B2 directly from Ca(BH4)2 or from CaB12H12 and amorphous boron allows an unexpectedly easy transfer of the boron atoms to reversibly form Ca(BH4)2 during rehydrogenation. In addition, to the best of our knowledge, the mutual destabilisation of the starting reactants is observed for the first time in Ca(BH4)2 based Reactive Hydride Composite (RHC) systems. A detailed account of dehydrogenation and rehydrogenation reaction mechanisms as the function of applied experimental conditions is given.
Structural evolution upon decomposition of the LiAlH4+LiBH4 system. S. Soru, A. Taras, C. Pistiddb, C. Milanese, C. Bonatto Minella, E. Masolo, P. Nolis, M. D. Baró, A. Marinic, M. Tolkiehn,M. Dornheim, S. Enzo, G. Mulas, S. Garroni. Journal of Alloys and Compounds 2014, in press. DOI: 10.1016/j.jallcom.2013.12.027
In the present work we focus the attention on the phase structural transformations occurring upon the desorption process of the LiBH4 + LiAlH4 system. Continue reading Structural evolution upon decomposition of the LiAlH4+LiBH4 system
“Chemical State, Distribution and Role of Ti- and Nb-Based Additives on the Ca(BH4)2 System” by Christian Bonatto Minella, Eva Pellicer, Emma Rossinyol, Fahim Karini, Claudio Pistidda,Sebastiano Garroni, Chiara Milanese, Pau Nolis, Maria Dolors Baró, Oliver Gutfleisch, Klaus Pranzas, Andreas Schreyer, Thomas Klassen, Rüdiger Bormann and Martin Dornheim. The Journal of Physical Chemistry C. 117:4394-4403 (2013). DOI: 10.1021/jp3116275
Light metal tetrahydroborates are regarded as promising materials for solid state hydrogen storage. Due to both a high gravimetric hydrogen capacity of 11.5 wt. % and an ideal de-hydrogenation enthalpy of 32 kJ mol-1 H2, Ca(BH4)2 is considered to be one of the most interesting compounds in this class of materials. In this work, a comprehensive investigation of the effect of different selected additives (TiF4, NbF5, Ti-isopropoxide and CaF2) on the reversible hydrogenation reaction of calcium borohydride is presented combining different investigation techniques. Continue reading Additives on the Ca(BH) system
“Ca(BH4)2 + MgH2: Desorption Reaction and Role of Mg on its Reversibility” by Christian Bonatto Minella, Claudio Pistidda, Sebastiano Garroni, Pau Nolis, Maria Dolors Baró, Oliver Gutfleisch, Thomas Klassen, Rüdiger Bormann, and Martin Dornheim. The Journal of Physical Chemistry C. 117:3846-3852 (2013). DOI: 10.1021/jp312271s
The Ca(BH4)2-MgH2 composite system represents a promising candidate for mobile hydrogen storage due to a 10.5 wt. % theoretical hydrogen storage capacity and an estimated equilibrium temperature lower than 160 °C. For this system, the reversibility was achieved without further addition of additives. Continue reading Ca(BH4)2 + MgH2: Desorption Reaction
“Experimental evidence of Na2[B12H12] and Na formation in the desorption pathway of the 2NaBH4+ MgH2 system”, by Sebastiano Garroni, Chiara Milanese, Daphiny Pottmaier, Gabriele Mulas, Pau Nolis, Alessandro Girella, Riccarda Caputo, David Olid-Britos, Francesc Teixidor, Marcello Baricco, Amedeo Marini, Santiago Suriñach, and Maria Dolores Baró. The Journal of Physical Chemistry C, Volume 115, Pages 16664-16671, July 2011. DOI: 10.1021/jp202341j
In the present work we report the desorption pathway of the 2NaBH4 + MgH2 system. Ex-situ X-ray powder diffraction (XRPD) and solid state magic angle spinning (MAS) nuclear magnetic resonance (NMR) measurements have been performed on samples heat-treated up to 450°C for different times. Ex-situ X-ray powder diffraction experiments conducted on fully desorbed samples allowed to identify nanocrystalline MgB2 and metallic Na as dehydrogenation products. Continue reading Experimental evidence of Na2[B12H12] and Na formation in the desorption pathway of the 2NaBH4 + MgH2 system
“Activation of the reactive hydride composite 2NaBH4 + MgH2” by C. Pistidda, G. Barkhordarian, A. Rzeszutek, S. Garroni, C. Bonatto Minella, M.D. Baró, P. Nolis, Rüdiger Bormann, T. Klassena and M. Dornhei. Scripta Materialia, Volume 64, Issue 11, June 2011, Pages 1035-1038. DOI: 10.1016/j.scriptamat.2011.02.017
A novel method to enhance the reaction kinetics of the reactive hydride composite 2NaBH4 + MgH2 is described. It has been discovered that short-term exposure to a moist atmosphere has a very beneficial effect on the desorption reaction of the 2NaBH4 + MgH2 mixture. By this procedure it is possible to achieve, after drying, both faster desorption kinetics and greater amounts of released hydrogen compared to ball-milled material without further treatment.