title: Synthesis, structure and properties of new bimetallic sodium and potassium lanthanum borohydrides.
abstract: Two new bimetallic sodium or potassium lanthanum borohydrides, NaLa(BH4)4and K3La(BH4)6, are formed using La(BH4)3free of metal halide by-products. NaLa(BH4)4crystallizes in an orthorhombic crystal system with unit cell parameters, a = 6.7987(19), b = 17.311(5), c = 7.2653(19) Å and space group symmetry Pbcn. This compound has a new structure type built from brucite-like layers of octahedra (hcp packing of anions) with half of the octahedral sites empty leading to octahedral chains similar to rutile (straight chains) or α-PbO2(zig-zag chains). K3La(BH4)6crystallizes in the monoclinic crystal system with unit cell parameters a = 7.938(2), b = 8.352(2), c = 11.571(3) Å, β = 90.19(6)° and space group P21/n with a double-perovskite type structure. Thermogravimetric analysis shows a mass loss of 5.86 and 2.83 wt% for NaLa(BH4)4and K3La(BH4)6, respectively, in the temperature range of room temperature to 400 °C. Mass spectrometry shows that hydrogen release starts at 212 and 275 °C for NaLa(BH4)4and K3La(BH4)6, respectively and confirms that no diborane is released. Sieverts' measurements reveal that 2.03 and 0.49 wt% of hydrogen can be released from the NaLa(BH4)4and K3La(BH4)6, respectively, during the second hydrogen desorption cycle at the selected physical condition for hydrogen absorption.
authors.affiliation: Department of Chemistry and Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Langelandsgade 140, 8000 Aarhus C, Denmark. trj@chem.au.dk.
authors.forename: SeyedHosein
authors.initials: S
authors.lastname: Payandeh GharibDoust
authors.forename: Michael
authors.initials: M
authors.lastname: Heere
authors.forename: Magnus H
authors.initials: MH
authors.lastname: Sørby
authors.forename: Morten B
authors.initials: MB
authors.lastname: Ley
authors.forename: Dorthe B
authors.initials: DB
authors.lastname: Ravnsbæk
authors.forename: Bjørn C
authors.initials: BC
authors.lastname: Hauback
authors.forename: Radovan
authors.initials: R
authors.lastname: Černý
authors.forename: Torben R
authors.initials: TR
authors.lastname: Jensen