Formation of CaB6 in the thermal decomposition of the hydrogen storage material Ca(BH4)2. Issue 29 (8th July 2016) - Sahle, Christoph J.
Abstract : Using a combination of high resolution X-ray powder diffraction and X-ray Raman scattering spectroscopy at the B K- and Ca L2, 3 -edges, we analyzed the reaction products of Ca(BH4 )2 after annealing at 350 °C and 400 °C under vacuum conditions. Abstract : Using a combination of high resolution X-ray powder diffraction and X-ray Raman scattering spectroscopy at the B K- and Ca L2, 3 -edges, we analyzed the reaction products of Ca(BH4 )2 after annealing at 350 °C and 400 °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 °C we observed neither CaB12 H12 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.