Perovskite alkali metal samarium borohydrides: crystal structures and thermal decomposition. Issue 35 (29th August 2017)

• Record Type: Journal Article
• Authors: Møller, Kasper T.; Jørgensen, Mathias; Fogh, Alexander S.; Jensen, Torben R.
• Is Part Of: Dalton transactions. Volume 46:Issue 35(2017)
• Page Start: 11905
• Page End: 11912
• Publication Date: 2017-08-29
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c7dt02405c
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : Synthesis and characterisation of samarium containing perovskite-type bimetallic borohydrides for hydrogen storage. Abstract : A new synthesis method of samarium borohydride, Sm(BH4 )2, using tetrahydrofuran borane, THF-BH3, and samarium hydride, SmH2, has been demonstrated and verified. The synthesised Sm(BH4 )2 was mechanochemically treated with MBH4, M = K, Rb, Cs. Initially, the formation of KSm(BH4 )3 is observed while subsequent heat treatment is necessary to form MSm(BH4 )3, M = Rb, Cs. The new compounds crystallise in orthorhombic unit cells adopting perovskite-type 3D frameworks containing distorted [Sm(BH4 )6 ] octahedra. In situ X-ray diffraction studies reveal two second-order polymorphic transitions of α-CsSm(BH4 )3 via a tetragonal intermediate, α′-CsSm(BH4 )3, into a cubic high-temperature polymorph, β-CsSm(BH4 )3, resembling an ideal perovskite structure. The new compounds, MSm(BH4 )3, are thermally stable up to T ∼ 280 °C after which they decompose into mainly MBH4, SmH2 and possibly SmB6 and SmB12 H12 . Finally, after three cycles of hydrogen release and uptake, the storage capacity was 1.0 wt% for KSm(BH4 )3 and 0.84 wt% for RbSm(BH4 )3 and CsSm(BH4 )3 .