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Torben R Jensen - One of the best experts on this subject based on the ideXlab platform.
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ammine lanthanum and cerium Borohydrides m bh4 3 nnh3 trends in synthesis structures and thermal properties
Inorganic Chemistry, 2020Co-Authors: Jakob B. Grinderslev, Young-su Lee, Young Whan Cho, Lars H. Jepsen, Jørgen Skibsted, Morten B Ley, Mathias Jorgensen, Torben R JensenAbstract:Ammine metal Borohydrides show potential for solid-state hydrogen storage and can be tailored toward hydrogen release at low temperatures. Here, we report the synthesis and structural characterization of seven new ammine metal Borohydrides, M(BH4)3·nNH3, M = La (n = 6, 4, or 3) or Ce (n = 6, 5, 4, or 3). The two compounds with n = 6 are isostructural and have new orthorhombic structure types (space group P21212) built from cationic complexes, [M(NH3)6(BH4)2]+, and are charge balanced by BH4-. The structure of Ce(BH4)3·5NH3 is orthorhombic (space group C2221) and is built from cationic complexes, [Ce(NH3)5(BH4)2]+, and charge balanced by BH4-. These are rare examples of Borohydride complexes acting both as a ligand and as a counterion in the same compound. The structures of M(BH4)3·4NH3 are monoclinic (space group C2), built from neutral molecular complexes of [M(NH3)4(BH4)3]. The new compositions, M(BH4)3·3NH3 (M = La, Ce), among ammine metal Borohydrides, are orthorhombic (space group Pna21), containing molecular complexes of [M(NH3)3(BH4)3]. A revised structural model for A(BH4)3·5NH3 (A = Y, Gd, Dy) is presented, and the previously reported composition A(BH4)3·4NH3 (A = Y, La, Gd, Dy) is proposed in fact to be M(BH4)3·3NH3 along with a new structural model. The temperature-dependent structural properties and decomposition are investigated by in situ synchrotron radiation powder X-ray diffraction in vacuum and argon atmosphere and by thermal analysis combined with mass spectrometry. The compounds with n = 6, 5, and 4 mainly release ammonia at low temperatures, while hydrogen evolution occurs for M(BH4)3·3NH3 (M = La, Ce). Gas-release temperatures and gas composition from these compounds depend on the physical conditions and on the relative stability of M(BH4)3·nNH3 and M(BH4)3.
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trends in synthesis crystal structure and thermal and magnetic properties of rare earth metal Borohydrides
Inorganic Chemistry, 2019Co-Authors: Jakob B. Grinderslev, Kasper T. Møller, Martin Bremholm, Torben R JensenAbstract:Synthesis, crystal structures, and thermal and magnetic properties of the complete series of halide-free rare-earth (RE) metal Borohydrides are presented. A new synthesis method provides high yield and high purity products. Fifteen new metal Borohydride structures are reported. The trends in crystal structures, thermal behavior, and magnetic properties for the entire series of RE(BH4)x are compared and discussed. The RE(BH4)x possess a very rich crystal chemistry, dependent on the oxidation state and the ionic size of the rare-earth ion. Due to the lanthanide contraction, there is a significant decrease in the volume of the RE3+-ion with increasing atomic number, which correlates linearly with the unit cell volume of the α- and β-RE(BH4)3 polymorphs and the solvated complexes α-RE(BH4)3·S(CH3)2. The thermal analysis reveals a one-step decomposition pathway in the temperature range from 247 to 277 °C for all RE(BH4)3 except Lu(BH4)3, which follows a three-step decomposition pathway. In contrast, the RE(BH4...
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Trends in Synthesis, Crystal Structure, and Thermal and Magnetic Properties of Rare-Earth Metal Borohydrides
2019Co-Authors: Jakob B. Grinderslev, Kasper T. Møller, Martin Bremholm, Torben R JensenAbstract:Synthesis, crystal structures, and thermal and magnetic properties of the complete series of halide-free rare-earth (RE) metal Borohydrides are presented. A new synthesis method provides high yield and high purity products. Fifteen new metal Borohydride structures are reported. The trends in crystal structures, thermal behavior, and magnetic properties for the entire series of RE(BH4)x are compared and discussed. The RE(BH4)x possess a very rich crystal chemistry, dependent on the oxidation state and the ionic size of the rare-earth ion. Due to the lanthanide contraction, there is a significant decrease in the volume of the RE3+-ion with increasing atomic number, which correlates linearly with the unit cell volume of the α- and β-RE(BH4)3 polymorphs and the solvated complexes α-RE(BH4)3·S(CH3)2. The thermal analysis reveals a one-step decomposition pathway in the temperature range from 247 to 277 °C for all RE(BH4)3 except Lu(BH4)3, which follows a three-step decomposition pathway. In contrast, the RE(BH4)2 decompose at higher temperatures in the range 306 to 390 °C due to lower charge density on the rare-earth ion. The RE(BH4)3 show increasing stability with increasing Pauling electronegativity, which contradicts other main group and transition metal Borohydrides. The majority of the compounds follow Curie–Weiss paramagnetic behavior down to 3 K with weak antiferromagnetic interactions and magnetic moments in accord with those of isolated 4f ions. Some of the RE(BH4)x display varying degrees of temperature-dependent magnetic moments due to low-lying excited stated induced by crystal field effects. Additionally, a weak antiferromagnetic ordering is observed in Gd(BH4)3, indicating superexchange through a Borohydride group
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hydrogenation properties of lithium and sodium hydride closo borate b10h10 2 and b12h12 2 composites
Physical Chemistry Chemical Physics, 2018Co-Authors: Steffen R H Jensen, Bjarne R. S. Hansen, Mark Paskevicius, Kasper T. Møller, Jørgen Skibsted, Anders S Jakobsen, James L White, Mark D Allendorf, Vitalie Stavila, Torben R JensenAbstract:The hydrogen absorption properties of metal closo-borate/metal hydride composites, M2B10H10–8MH and M2B12H12–10MH, M = Li or Na, are studied under high hydrogen pressures to understand the formation mechanism of metal Borohydrides. The hydrogen storage properties of the composites have been investigated by in situ synchrotron radiation powder X-ray diffraction at p(H2) = 400 bar and by ex situ hydrogen absorption measurements at p(H2) = 526 to 998 bar. The in situ experiments reveal the formation of crystalline intermediates before metal Borohydrides (MBH4) are formed. On the contrary, the M2B12H12–10MH (M = Li and Na) systems show no formation of the metal Borohydride at T = 400 °C and p(H2) = 537 to 970 bar. 11B MAS NMR of the M2B10H10–8MH composites reveal that the molar ratio of LiBH4 or NaBH4 and the remaining B species is 1 : 0.63 and 1 : 0.21, respectively. Solution and solid-state 11B NMR spectra reveal new intermediates with a B : H ratio close to 1 : 1. Our results indicate that the M2B10H10 (M = Li, Na) salts display a higher reactivity towards hydrogen in the presence of metal hydrides compared to the corresponding [B12H12]2− composites, which represents an important step towards understanding the factors that determine the stability and reversibility of high hydrogen capacity metal Borohydrides for hydrogen storage.
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From Metal Hydrides to Metal Borohydrides
2018Co-Authors: Bo Richter, Mark Paskevicius, Jakob B. Grinderslev, Kasper T. Møller, Torben R JensenAbstract:Commencing from metal hydrides, versatile synthesis, purification, and desolvation approaches are presented for a wide range of metal Borohydrides and their solvates. An optimized and generalized synthesis method is provided for 11 different metal Borohydrides, M(BH4)n, (M = Li, Na, Mg, Ca, Sr, Ba, Y, Nd, Sm, Gd, Yb), providing controlled access to more than 15 different polymorphs and in excess of 20 metal Borohydride solvate complexes. Commercially unavailable metal hydrides (MHn, M = Sr, Ba, Y, Nd, Sm, Gd, Yb) are synthesized utilizing high pressure hydrogenation. For synthesis of metal Borohydrides, all hydrides are mechanochemically activated prior to reaction with dimethylsulfide borane. A purification process is devised, alongside a complementary desolvation process for solvate complexes, yielding high purity products. An array of polymorphically pure metal Borohydrides are synthesized in this manner, supporting the general applicability of this method. Additionally, new metal Borohydrides, α-, α′- β-, γ-Yb(BH4)2, α-Nd(BH4)3 and new solvates Sr(BH4)2·1THF, Sm(BH4)2·1THF, Yb(BH4)2·xTHF, x = 1 or 2, Nd(BH4)3·1Me2S, Nd(BH4)3·1.5THF, Sm(BH4)3·1.5THF and Yb(BH4)3·xMe2S (“x” = unspecified), are presented here. Synthesis conditions are optimized individually for each metal, providing insight into reactivity and mechanistic concerns. The reaction follows a nucleophilic addition/hydride-transfer mechanism. Therefore, the reaction is most efficient for ionic and polar-covalent metal hydrides. The presented synthetic approaches are widely applicable, as demonstrated by permitting facile access to a large number of materials and by performing a scale-up synthesis of LiBH4
Yaroslav Filinchuk - One of the best experts on this subject based on the ideXlab platform.
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solid aluminum Borohydrides for prospective hydrogen storage
Chemsuschem, 2017Co-Authors: Radovan Cerný, Iurii Dovgaliuk, Michel Devillers, Damir A Safin, Nikolay Tumanov, Fabrice Morelle, Adel Moulai, Zbigniew łodziana, Yaroslav FilinchukAbstract:Metal Borohydrides are intensively researched as high-capacity hydrogen storage materials. Aluminum is a cheap, light, and abundant element and Al3+ can serve as a template for reversible dehydrogenation. However, Al(BH4 )3 , containing 16.9 wt % of hydrogen, has a low boiling point, is explosive on air and has poor storage stability. A new family of mixed-cation Borohydrides M[Al(BH4 )4 ], which are all solid under ambient conditions, show diverse thermal decomposition behaviors: Al(BH4 )3 is released for M=Li+ or Na+ , whereas heavier derivatives evolve hydrogen and diborane. NH4 [Al(BH4 )4 ], containing both protic and hydridic hydrogen, has the lowest decomposition temperature of 35 °C and yields Al(BH4 )3 ⋅NHBH and hydrogen. The decomposition temperatures, correlated with the cations' ionic potential, show that M[Al(BH4 )4 ] species are in the most practical stability window. This family of solids, with convenient and versatile properties, puts aluminum Borohydride chemistry in the mainstream of hydrogen storage research, for example, for the development of reactive hydride composites with increased hydrogen content.
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metal Borohydrides and derivatives synthesis structure and properties
Chemical Society Reviews, 2017Co-Authors: Mark Paskevicius, Pascal Schouwink, Lars H. Jepsen, Dorthe Bomholdt Ravnsbæk, Yaroslav Filinchuk, Martin Dornheim, Flemming Besenbacher, Radovan Cerný, Torben R JensenAbstract:A wide variety of metal Borohydrides, MBH4, have been discovered and characterized during the past decade, revealing an extremely rich chemistry including fascinating structural flexibility and a wide range of compositions and physical properties. Metal Borohydrides receive increasing interest within the energy storage field due to their extremely high hydrogen density and possible uses in batteries as solid state ion conductors. Recently, new types of physical properties have been explored in lanthanide-bearing Borohydrides related to solid state phosphors and magnetic refrigeration. Two major classes of metal Borohydride derivatives have also been discovered: anion-substituted compounds where the complex Borohydride anion, BH4−, is replaced by another anion, i.e. a halide or amide ion; and metal Borohydrides modified with neutral molecules, such as NH3, NH3BH3, N2H4, etc. Here, we review new synthetic strategies along with structural, physical and chemical properties for metal Borohydrides, revealing a number of new trends correlating composition, structure, bonding and thermal properties. These new trends provide general knowledge and may contribute to the design and discovery of new metal Borohydrides with tailored properties towards the rational design of novel functional materials. This review also demonstrates that there is still room for discovering new combinations of light elements including boron and hydrogen, leading to complex hydrides with extreme flexibility in composition, structure and properties.
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Novel Alkali Earth Borohydride Sr(BH4)2 and Borohydride-Chloride Sr(BH4)Cl
2016Co-Authors: Dorthe Bomholdt Ravnsbæk, Yaroslav Filinchuk, E. A. Nickels, R. Černý, C. H. Olesen, W. I. F. David, P. P. Edwards, T. R. JensenAbstract:Two novel alkali earth Borohydrides, Sr(BH4)2 and Sr(BH4)Cl, have been synthesized and investigated by in-situ synchrotron radiation powder X-ray diffraction (SR-PXD) and Raman spectroscopy. Strontium Borohydride, Sr(BH4)2, was synthesized via a metathesis reaction between LiBH4 and SrCl2 by two complementary methods, i.e., solvent-mediated and mechanochemical synthesis, while Sr(BH4)Cl was obtained from mechanochemical synthesis, i.e., ball milling. Sr(BH4)2 crystallizes in the orthorhombic crystal system, a = 6.97833(9) Å, b = 8.39651(11) Å, and c = 7.55931(10) Å (V = 442.927(10) Å3) at RT with space group symmetry Pbcn. The compound crystallizes in α-PbO2 structure type and is built from half-occupied brucite-like layers of slightly distorted [Sr(BH4)6] octahedra stacked in the a-axis direction. Strontium Borohydride chloride, Sr(BH4)Cl, is a stoichiometric, ordered compound, which also crystallizes in the orthorhombic crystal system, a = 10.8873(8) Å, b = 4.6035(3) Å, and c = 7.4398(6) Å (V = 372.91(3) Å3) at RT, with space group symmetry Pnma and structure type Sr(OH)2. Sr(BH4)Cl dissociates into Sr(BH4)2 and SrCl2 at ∼170 °C, while Sr(BH4)2 is found to decompose in multiple steps between 270 and 465 °C with formation of several decomposition products, e.g., SrB6. Furthermore, partly characterized new compounds are also reported here, e.g., a solvate of Sr(BH4)2 and two Li–Sr–BH4 compounds
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tailoring the properties of ammine metal Borohydrides for solid state hydrogen storage
Chemsuschem, 2015Co-Authors: Lars H. Jepsen, Yaroslav Filinchuk, Flemming Besenbacher, Torben R JensenAbstract:A series of halide-free ammine manganese Borohydrides, Mn(BH4)2·nNH3, n=1, 2, 3, and 6, a new bimetallic compound Li2Mn(BH4)4·6NH3, and the first ammine metal Borohydride solid solution Mg1xMnx(BH4)2·6NH3 are presented. Four new crystal structures have been determined by synchrotron radiation powder X-ray diffraction and the thermal decomposition is systematically investigated for all the new compounds. The solid-gas reaction between Mn(BH4)2 and NH3 provides Mn(BH4)2·6NH3. The number of NH3 per Mn has been varied by mechanochemical treatment of Mn(BH4)2·6NH3-Mn(BH4)2 mixtures giving rise to increased hydrogen purity for n/m1 for M(BH4)m·nNH3. The structures of Mg(BH4)2·3NH3 and Li2Mg(BH4)4·6NH3 have been revisited and new structural models are presented. Finally, we demonstrate that ammonia destabilizes metal Borohydrides with low electronegativity of the metal (cp ~1.6) are generally stabilized.
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novel alkali earth Borohydride sr bh4 2 and Borohydride chloride sr bh4 cl
Inorganic Chemistry, 2013Co-Authors: Dorthe Bomholdt Ravnsbæk, Radovan Cerný, E. A. Nickels, C. H. Olesen, W. I. F. David, P. P. Edwards, Yaroslav FilinchukAbstract:Two novel alkali earth Borohydrides, Sr(BH4)2 and Sr(BH4)Cl, have been synthesized and investigated by in-situ synchrotron radiation powder X-ray diffraction (SR-PXD) and Raman spectroscopy. Strontium Borohydride, Sr(BH4)2, was synthesized via a metathesis reaction between LiBH4 and SrCl2 by two complementary methods, i.e., solvent-mediated and mechanochemical synthesis, while Sr(BH4)Cl was obtained from mechanochemical synthesis, i.e., ball milling. Sr(BH4)2 crystallizes in the orthorhombic crystal system, a = 6.97833(9) A, b = 8.39651(11) A, and c = 7.55931(10) A (V = 442.927(10) A3) at RT with space group symmetry Pbcn. The compound crystallizes in α-PbO2 structure type and is built from half-occupied brucite-like layers of slightly distorted [Sr(BH4)6] octahedra stacked in the a-axis direction. Strontium Borohydride chloride, Sr(BH4)Cl, is a stoichiometric, ordered compound, which also crystallizes in the orthorhombic crystal system, a = 10.8873(8) A, b = 4.6035(3) A, and c = 7.4398(6) A (V = 372.91(3) A3) at RT, with space group symmetry Pnma and structure type Sr(OH)2. Sr(BH4)Cl dissociates into Sr(BH4)2 and SrCl2 at ∼170 C, while Sr(BH4)2 is found to decompose in multiple steps between 270 and 465 C with formation of several decomposition products, e.g., SrB 6. Furthermore, partly characterized new compounds are also reported here, e.g., a solvate of Sr(BH4)2 and two Li-Sr-BH 4 compounds. © 2013 American Chemical Society.
Radovan Cerný - One of the best experts on this subject based on the ideXlab platform.
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solid aluminum Borohydrides for prospective hydrogen storage
Chemsuschem, 2017Co-Authors: Radovan Cerný, Iurii Dovgaliuk, Michel Devillers, Damir A Safin, Nikolay Tumanov, Fabrice Morelle, Adel Moulai, Zbigniew łodziana, Yaroslav FilinchukAbstract:Metal Borohydrides are intensively researched as high-capacity hydrogen storage materials. Aluminum is a cheap, light, and abundant element and Al3+ can serve as a template for reversible dehydrogenation. However, Al(BH4 )3 , containing 16.9 wt % of hydrogen, has a low boiling point, is explosive on air and has poor storage stability. A new family of mixed-cation Borohydrides M[Al(BH4 )4 ], which are all solid under ambient conditions, show diverse thermal decomposition behaviors: Al(BH4 )3 is released for M=Li+ or Na+ , whereas heavier derivatives evolve hydrogen and diborane. NH4 [Al(BH4 )4 ], containing both protic and hydridic hydrogen, has the lowest decomposition temperature of 35 °C and yields Al(BH4 )3 ⋅NHBH and hydrogen. The decomposition temperatures, correlated with the cations' ionic potential, show that M[Al(BH4 )4 ] species are in the most practical stability window. This family of solids, with convenient and versatile properties, puts aluminum Borohydride chemistry in the mainstream of hydrogen storage research, for example, for the development of reactive hydride composites with increased hydrogen content.
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metal Borohydrides and derivatives synthesis structure and properties
Chemical Society Reviews, 2017Co-Authors: Mark Paskevicius, Pascal Schouwink, Lars H. Jepsen, Dorthe Bomholdt Ravnsbæk, Yaroslav Filinchuk, Martin Dornheim, Flemming Besenbacher, Radovan Cerný, Torben R JensenAbstract:A wide variety of metal Borohydrides, MBH4, have been discovered and characterized during the past decade, revealing an extremely rich chemistry including fascinating structural flexibility and a wide range of compositions and physical properties. Metal Borohydrides receive increasing interest within the energy storage field due to their extremely high hydrogen density and possible uses in batteries as solid state ion conductors. Recently, new types of physical properties have been explored in lanthanide-bearing Borohydrides related to solid state phosphors and magnetic refrigeration. Two major classes of metal Borohydride derivatives have also been discovered: anion-substituted compounds where the complex Borohydride anion, BH4−, is replaced by another anion, i.e. a halide or amide ion; and metal Borohydrides modified with neutral molecules, such as NH3, NH3BH3, N2H4, etc. Here, we review new synthetic strategies along with structural, physical and chemical properties for metal Borohydrides, revealing a number of new trends correlating composition, structure, bonding and thermal properties. These new trends provide general knowledge and may contribute to the design and discovery of new metal Borohydrides with tailored properties towards the rational design of novel functional materials. This review also demonstrates that there is still room for discovering new combinations of light elements including boron and hydrogen, leading to complex hydrides with extreme flexibility in composition, structure and properties.
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synthesis and thermal stability of perovskite alkali metal strontium Borohydrides
Dalton Transactions, 2016Co-Authors: Kasper T. Møller, Radovan Cerný, Pascal Schouwink, Morten B Ley, Torben R JensenAbstract:Three new perovskite-type bimetallic alkali metal strontium Borohydride compounds, α-MSr(BH4)3 (M = K, Rb, Cs), have been synthesized and investigated by in situ synchrotron radiation powder X-ray diffraction, thermal analysis combined with mass spectrometry and Sievert's measurements. The bimetallic Borohydrides were synthesized via an addition reaction between Sr(BH4)2 and MBH4 (M = K, Rb, Cs) by mechanochemical treatment. The Sr(BH4)2–NaBH4 system, which was treated in a similar manner, did not undergo reaction. All three α-MSr(BH4)3 compounds crystallize in the orthorhombic crystal system at room temperature: KSr(BH4)3 (P21cn), a = 7.8967(6), b = 8.2953(7), and c = 11.508(1) A (V = 753.82(12) A3). RbSr(BH4)3 (Pbn21), a = 8.0835(3), b = 8.3341(4), and c = 11.6600(5) A (V = 785.52(6) A3). CsSr(BH4)3 (P22121), a = 8.2068(9), b = 8.1793(9), and c = 6.0761(4) A (V = 407.87(7) A3). All three compounds are perovskite-type 3D framework structures built from distorted [Sr(BH4)6] octahedra. High-temperature polymorphs are identified to form at 258, 220 and 150 °C for MSr(BH4)3, M = K, Rb and Cs, respectively. The new compounds are thermally stable and decompose at T > 360 °C into SrB6, SrH2 and MBH4 (M = K, Rb, Cs).
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the crystal chemistry of inorganic metal Borohydrides and their relation to metal oxides
Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry, 2015Co-Authors: Radovan Cerný, Pascal SchouwinkAbstract:The crystal structures of inorganic homoleptic metal Borohydrides are analysed with respect to their structural prototypes found amongst metal oxides in the inorganic databases such as Pearson's Crystal Data [Villars & Cenzual (2015). Pearson's Crystal Data. Crystal Structure Database for Inorganic Compounds, Release 2014/2015, ASM International, Materials Park, Ohio, USA]. The coordination polyhedra around the cations and the Borohydride anion are determined, and constitute the basis of the structural systematics underlying metal Borohydride chemistry in various frameworks and variants of ionic packing, including complex anions and the packing of neutral molecules in the crystal. Underlying nets are determined by topology analysis using the program TOPOS [Blatov (2006). IUCr CompComm. Newsl. 7, 4-38]. It is found that the Pauling rules for ionic crystals apply to all non-molecular Borohydride crystal structures, and that the latter can often be derived by simple deformation of the close-packed anionic lattices c.c.p. and h.c.p., by partially removing anions and filling tetrahedral or octahedral sites. The deviation from an ideal close packing is facilitated in metal Borohydrides with respect to the oxide due to geometrical and electronic considerations of the BH4(-) anion (tetrahedral shape, polarizability). This review on crystal chemistry of Borohydrides and their similarity to oxides is a contribution which should serve materials engineers as a roadmap to design new materials, synthetic chemists in their search for promising compounds to be prepared, and materials scientists in understanding the properties of novel materials.
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alkali metal yttrium Borohydrides the link between coordination of small and large rare earth
Journal of Solid State Chemistry, 2015Co-Authors: Yolanda Sadikin, Torben R Jensen, Pascal Schouwink, Katarina Stare, Morten B Ley, Anton Meden, Radovan CernýAbstract:The system Li–A–Y–BH4 (A=K, Rb, Cs) is found to contain five new compounds and four further ones known from previous work on the homoleptic Borohydrides. Crystal structures have been solved and refined from synchrotron X-ray powder diffraction, thermal stability of new compounds have been investigated and ionic conductivity measured for selected samples. Significant coordination flexibility for Y3+ is revealed, which allows the formation of both octahedral frameworks and tetrahedral complex anions with the tetrahydroborate anion BH4 both as a linker and terminal ligand. Bi- and trimetallic cubic double-perovskites c-A3Y(BH4)6 or c-A2LiY(BH4)6 (A=Rb, Cs) form in all the investigated systems, with the exception of the Li–K–Y system. The compounds with the stoichiometry AY(BH4)4 crystallize in all investigated systems with a great variety of structure types which find their analog amongst metal oxides. In-situ formation of a new Borohydride – closo-borane is observed during decomposition of all double perovskites.
Mark Paskevicius - One of the best experts on this subject based on the ideXlab platform.
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hydrogenation properties of lithium and sodium hydride closo borate b10h10 2 and b12h12 2 composites
Physical Chemistry Chemical Physics, 2018Co-Authors: Steffen R H Jensen, Bjarne R. S. Hansen, Mark Paskevicius, Kasper T. Møller, Jørgen Skibsted, Anders S Jakobsen, James L White, Mark D Allendorf, Vitalie Stavila, Torben R JensenAbstract:The hydrogen absorption properties of metal closo-borate/metal hydride composites, M2B10H10–8MH and M2B12H12–10MH, M = Li or Na, are studied under high hydrogen pressures to understand the formation mechanism of metal Borohydrides. The hydrogen storage properties of the composites have been investigated by in situ synchrotron radiation powder X-ray diffraction at p(H2) = 400 bar and by ex situ hydrogen absorption measurements at p(H2) = 526 to 998 bar. The in situ experiments reveal the formation of crystalline intermediates before metal Borohydrides (MBH4) are formed. On the contrary, the M2B12H12–10MH (M = Li and Na) systems show no formation of the metal Borohydride at T = 400 °C and p(H2) = 537 to 970 bar. 11B MAS NMR of the M2B10H10–8MH composites reveal that the molar ratio of LiBH4 or NaBH4 and the remaining B species is 1 : 0.63 and 1 : 0.21, respectively. Solution and solid-state 11B NMR spectra reveal new intermediates with a B : H ratio close to 1 : 1. Our results indicate that the M2B10H10 (M = Li, Na) salts display a higher reactivity towards hydrogen in the presence of metal hydrides compared to the corresponding [B12H12]2− composites, which represents an important step towards understanding the factors that determine the stability and reversibility of high hydrogen capacity metal Borohydrides for hydrogen storage.
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From Metal Hydrides to Metal Borohydrides
2018Co-Authors: Bo Richter, Mark Paskevicius, Jakob B. Grinderslev, Kasper T. Møller, Torben R JensenAbstract:Commencing from metal hydrides, versatile synthesis, purification, and desolvation approaches are presented for a wide range of metal Borohydrides and their solvates. An optimized and generalized synthesis method is provided for 11 different metal Borohydrides, M(BH4)n, (M = Li, Na, Mg, Ca, Sr, Ba, Y, Nd, Sm, Gd, Yb), providing controlled access to more than 15 different polymorphs and in excess of 20 metal Borohydride solvate complexes. Commercially unavailable metal hydrides (MHn, M = Sr, Ba, Y, Nd, Sm, Gd, Yb) are synthesized utilizing high pressure hydrogenation. For synthesis of metal Borohydrides, all hydrides are mechanochemically activated prior to reaction with dimethylsulfide borane. A purification process is devised, alongside a complementary desolvation process for solvate complexes, yielding high purity products. An array of polymorphically pure metal Borohydrides are synthesized in this manner, supporting the general applicability of this method. Additionally, new metal Borohydrides, α-, α′- β-, γ-Yb(BH4)2, α-Nd(BH4)3 and new solvates Sr(BH4)2·1THF, Sm(BH4)2·1THF, Yb(BH4)2·xTHF, x = 1 or 2, Nd(BH4)3·1Me2S, Nd(BH4)3·1.5THF, Sm(BH4)3·1.5THF and Yb(BH4)3·xMe2S (“x” = unspecified), are presented here. Synthesis conditions are optimized individually for each metal, providing insight into reactivity and mechanistic concerns. The reaction follows a nucleophilic addition/hydride-transfer mechanism. Therefore, the reaction is most efficient for ionic and polar-covalent metal hydrides. The presented synthetic approaches are widely applicable, as demonstrated by permitting facile access to a large number of materials and by performing a scale-up synthesis of LiBH4
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metal Borohydrides and derivatives synthesis structure and properties
Chemical Society Reviews, 2017Co-Authors: Mark Paskevicius, Pascal Schouwink, Lars H. Jepsen, Dorthe Bomholdt Ravnsbæk, Yaroslav Filinchuk, Martin Dornheim, Flemming Besenbacher, Radovan Cerný, Torben R JensenAbstract:A wide variety of metal Borohydrides, MBH4, have been discovered and characterized during the past decade, revealing an extremely rich chemistry including fascinating structural flexibility and a wide range of compositions and physical properties. Metal Borohydrides receive increasing interest within the energy storage field due to their extremely high hydrogen density and possible uses in batteries as solid state ion conductors. Recently, new types of physical properties have been explored in lanthanide-bearing Borohydrides related to solid state phosphors and magnetic refrigeration. Two major classes of metal Borohydride derivatives have also been discovered: anion-substituted compounds where the complex Borohydride anion, BH4−, is replaced by another anion, i.e. a halide or amide ion; and metal Borohydrides modified with neutral molecules, such as NH3, NH3BH3, N2H4, etc. Here, we review new synthetic strategies along with structural, physical and chemical properties for metal Borohydrides, revealing a number of new trends correlating composition, structure, bonding and thermal properties. These new trends provide general knowledge and may contribute to the design and discovery of new metal Borohydrides with tailored properties towards the rational design of novel functional materials. This review also demonstrates that there is still room for discovering new combinations of light elements including boron and hydrogen, leading to complex hydrides with extreme flexibility in composition, structure and properties.
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eutectic melting in metal Borohydrides
Physical Chemistry Chemical Physics, 2013Co-Authors: Mark Paskevicius, Drew A. Sheppard, Torben R Jensen, Craig E. BuckleyAbstract:A series of monometallic Borohydrides and Borohydride eutectic mixtures have been investigated during thermal ramping by mass spectroscopy, differential scanning calorimetry, and photography. Mixtures of LiBH4–NaBH4, LiBH4–KBH4, LiBH4–Mg(BH4)2, LiBH4–Ca(BH4)2, LiBH4–Mn(BH4)2, NaBH4–KBH4, and LiBH4–NaBH4–KBH4 all displayed melting behaviour below that of the monometallic phases (up to 167 °C lower). Generally, each system behaves differently with respect to their physical behaviour upon melting. The molten phases can exhibit colour changes, bubbling and in some cases frothing, or even liquid–solid phase transitions during hydrogen release. Remarkably, the eutectic melt can also allow for hydrogen release at temperatures lower than that of the individual components. Some systems display decomposition of the Borohydride in the solid-state before melting and certain hydrogen release events have also been linked to the adverse reaction of samples with impurities, usually within the starting reagents, and these may also be coupled with bubbling or frothing of the ionic melt.
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metal Borohydrides and derivatives synthesis structure and properties
Chemical Society Reviews, 2017Co-Authors: Mark Paskevicius, Pascal Schouwink, Lars H. Jepsen, Dorthe Bomholdt Ravnsbæk, Yaroslav Filinchuk, Martin Dornheim, Flemming Besenbacher, Radovan Cerný, Torben R JensenAbstract:A wide variety of metal Borohydrides, MBH4, have been discovered and characterized during the past decade, revealing an extremely rich chemistry including fascinating structural flexibility and a wide range of compositions and physical properties. Metal Borohydrides receive increasing interest within the energy storage field due to their extremely high hydrogen density and possible uses in batteries as solid state ion conductors. Recently, new types of physical properties have been explored in lanthanide-bearing Borohydrides related to solid state phosphors and magnetic refrigeration. Two major classes of metal Borohydride derivatives have also been discovered: anion-substituted compounds where the complex Borohydride anion, BH4−, is replaced by another anion, i.e. a halide or amide ion; and metal Borohydrides modified with neutral molecules, such as NH3, NH3BH3, N2H4, etc. Here, we review new synthetic strategies along with structural, physical and chemical properties for metal Borohydrides, revealing a number of new trends correlating composition, structure, bonding and thermal properties. These new trends provide general knowledge and may contribute to the design and discovery of new metal Borohydrides with tailored properties towards the rational design of novel functional materials. This review also demonstrates that there is still room for discovering new combinations of light elements including boron and hydrogen, leading to complex hydrides with extreme flexibility in composition, structure and properties.
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Novel Alkali Earth Borohydride Sr(BH4)2 and Borohydride-Chloride Sr(BH4)Cl
2016Co-Authors: Dorthe Bomholdt Ravnsbæk, Yaroslav Filinchuk, E. A. Nickels, R. Černý, C. H. Olesen, W. I. F. David, P. P. Edwards, T. R. JensenAbstract:Two novel alkali earth Borohydrides, Sr(BH4)2 and Sr(BH4)Cl, have been synthesized and investigated by in-situ synchrotron radiation powder X-ray diffraction (SR-PXD) and Raman spectroscopy. Strontium Borohydride, Sr(BH4)2, was synthesized via a metathesis reaction between LiBH4 and SrCl2 by two complementary methods, i.e., solvent-mediated and mechanochemical synthesis, while Sr(BH4)Cl was obtained from mechanochemical synthesis, i.e., ball milling. Sr(BH4)2 crystallizes in the orthorhombic crystal system, a = 6.97833(9) Å, b = 8.39651(11) Å, and c = 7.55931(10) Å (V = 442.927(10) Å3) at RT with space group symmetry Pbcn. The compound crystallizes in α-PbO2 structure type and is built from half-occupied brucite-like layers of slightly distorted [Sr(BH4)6] octahedra stacked in the a-axis direction. Strontium Borohydride chloride, Sr(BH4)Cl, is a stoichiometric, ordered compound, which also crystallizes in the orthorhombic crystal system, a = 10.8873(8) Å, b = 4.6035(3) Å, and c = 7.4398(6) Å (V = 372.91(3) Å3) at RT, with space group symmetry Pnma and structure type Sr(OH)2. Sr(BH4)Cl dissociates into Sr(BH4)2 and SrCl2 at ∼170 °C, while Sr(BH4)2 is found to decompose in multiple steps between 270 and 465 °C with formation of several decomposition products, e.g., SrB6. Furthermore, partly characterized new compounds are also reported here, e.g., a solvate of Sr(BH4)2 and two Li–Sr–BH4 compounds
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novel alkali earth Borohydride sr bh4 2 and Borohydride chloride sr bh4 cl
Inorganic Chemistry, 2013Co-Authors: Dorthe Bomholdt Ravnsbæk, Radovan Cerný, E. A. Nickels, C. H. Olesen, W. I. F. David, P. P. Edwards, Yaroslav FilinchukAbstract:Two novel alkali earth Borohydrides, Sr(BH4)2 and Sr(BH4)Cl, have been synthesized and investigated by in-situ synchrotron radiation powder X-ray diffraction (SR-PXD) and Raman spectroscopy. Strontium Borohydride, Sr(BH4)2, was synthesized via a metathesis reaction between LiBH4 and SrCl2 by two complementary methods, i.e., solvent-mediated and mechanochemical synthesis, while Sr(BH4)Cl was obtained from mechanochemical synthesis, i.e., ball milling. Sr(BH4)2 crystallizes in the orthorhombic crystal system, a = 6.97833(9) A, b = 8.39651(11) A, and c = 7.55931(10) A (V = 442.927(10) A3) at RT with space group symmetry Pbcn. The compound crystallizes in α-PbO2 structure type and is built from half-occupied brucite-like layers of slightly distorted [Sr(BH4)6] octahedra stacked in the a-axis direction. Strontium Borohydride chloride, Sr(BH4)Cl, is a stoichiometric, ordered compound, which also crystallizes in the orthorhombic crystal system, a = 10.8873(8) A, b = 4.6035(3) A, and c = 7.4398(6) A (V = 372.91(3) A3) at RT, with space group symmetry Pnma and structure type Sr(OH)2. Sr(BH4)Cl dissociates into Sr(BH4)2 and SrCl2 at ∼170 C, while Sr(BH4)2 is found to decompose in multiple steps between 270 and 465 C with formation of several decomposition products, e.g., SrB 6. Furthermore, partly characterized new compounds are also reported here, e.g., a solvate of Sr(BH4)2 and two Li-Sr-BH 4 compounds. © 2013 American Chemical Society.