Formation of CaB6 in the thermal decomposition of the hydrogen storage material Ca(BH4)(2)

Christoph J. Sahle (1) , Christian Sternemann (2) , Carlotta Giacobbe (1) , Yigang Yan (3) , Christopher Weis (2) , Manuel Harder (4, 2) , Yury Forov (2) , Georg Spiekermann (4, 5) , Metin Tolan (2) , Michael Krisch (1) , Arndt Remhof (3, 6)

1 ESRF - European Synchrotron Radiation Facility
2 TU - Technische Universität Dortmund [Dortmund]
3 EMPA Materials for Energy Conversion
4 DESY - Deutsches Elektronen-Synchrotron [Hamburg]
5 GFZ - German Research Centre for Geosciences - Helmholtz-Centre Potsdam
6 Univ Freiburg, Crystallog, Inst Geo & Environm Sci, D-79098 Freiburg, Germany

Using a combination of high resolution X-ray powder diffraction and X-ray Raman scattering spectroscopy at the B K- and Ca L-2,L-3-edges, we analyzed the reaction products of Ca(BH4)(2) after annealing at 350 degrees C and 400 degrees C under vacuum conditions. We observed the formation of nanocrystalline/amorphous CaB6 mainly and found only small contributions from amorphous B for annealing times larger than 2 h. For short annealing times of 0.5 h at 400 degrees C we observed neither CaB12H12 nor CaB6. The results indicate a reaction pathway in which Ca(BH4)(2) decomposes to B and CaH2 and finally reacts to form CaB6. These findings confirm the potential of using Ca(BH4)(2) as a hydrogen storage medium and imply the desired cycling capabilities for achieving high-density hydrogen storage materials

Domaines: Chimie

Christoph J. Sahle, Christian Sternemann, Carlotta Giacobbe, Yigang Yan, Christopher Weis, et al.. Formation of CaB6 in the thermal decomposition of the hydrogen storage material Ca(BH4)(2). Physical Chemistry Chemical Physics, 2016, 18 (29), pp.19866-19872. ⟨10.1039/c6cp02495e⟩. ⟨hal-01572982⟩