1
Understanding Li 2 B 12 H 12 Bjarne R. S. Hansen a and Torben R. Jensen a a Interdisciplinary Nano Science Center, Center for Materials Crystallography and Department of Chemistry, University of Aarhus, Langelandsgade 140, DK-8000 Aarhus C, Denmark Acknowledgements and references Sincere acknowledgements are directed to the Interdisciplinary Nano Science Center (iNANO), Danscatt, MAX-Lab Bor4Store (EU) and Center for Materials Crystallography (CMC) Introduction Light metal borohydrides, such as LiBH 4 , has a massive potential as hydrogen storage materials for storage applications in a wide scale. Most borohydrides require high temperatures for hydrogen release, but this can in many cases be lowered by utilizing eutectic composites, reactive hydride composites or by nanoconfinement. However, one major challenge still remains: Reversibility! Sample preparation In situ SR-PXD In practically all metalborohydrides M-B 12 H 12 species are formed during decomposition which ultimately reduces the reversible hydrogen storage capacity [1] . In order to understand or avoid this more knowledge of these compounds is required. Therefore this current study investigates Li 2 B 12 H 12 . β- Li 2 B 12 H 12 Li 2 B 12 H 12 γ- Li 2 B 12 H 12-x RT → 700 °C (5K/min), p(H 2 ) = vac. λ = 0.9941 Å Li 2 B 12 H 12 - 4 H 2 O (Katchem) was heated to 240 °C under dynamic vacuum for 10 h to completely dry the sample and obtain an anhydrous, crystalline phase [2] As the temperature increases the hump is shifting towards lower 2θ angle. The end product is ex- pected to be amorphous B. These observations agree well with thermal analysis and a previous study [4] . The fact that the sample becomes amor-phous during heating complicates characteri-zation of the decomposition reactions with PXRD. Therefore 11 B MAS NMR studies are currently being conducted. [1] B. R. S. Hansen et al., J. Phys. Chem. C 2013, 117, 7423−7432 [2] Pitt et al, J. Am. Chem. Soc. 2013, 135, 6930−6941 [3] Whang et al., J. Phys. Chem. C, 2008, 112 (9), 3164–3169 [4] Paskevicious et al, Phys. Chem. Chem. Phys. 2013, 15, 15825 Thermal analysis The B 12 H 12 2- ion [3] DSC and TGA indicate three reaction steps are present, where the first step may be owing to water contamination. These steps will be fur-ther investigated using FT-IR and 11 B MAS NMR. An in situ SR-PXD experiment on Li 2 B 12 H 12 was performed at Maxlab, I711. At T = 280 °C a phase transformation is obser-ved, and at T = 355 °C the sample turns amor-phous and a broad hump is observed. [1]
