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Torben R Jensen - One of the best experts on this subject based on the ideXlab platform.
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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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From Metal Hydrides to Metal Borohydrides.
Inorganic chemistry, 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′-...
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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.
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, Radovan Černý, Pascal Schouwink, Lars H. Jepsen, Dorthe Bomholdt Ravnsbæk, Yaroslav Filinchuk, Martin Dornheim, Flemming Besenbacher, 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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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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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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The First Halide-Free Bimetallic Aluminum Borohydride: Synthesis, Structure, Stability, and Decomposition Pathway
Journal of Physical Chemistry C, 2014Co-Authors: Iurii Dovgaliuk, Radovan Cerný, Voraksmy Ban, Yolanda Sadikin, Lionel Aranda, Nicola Casati, Michel Devillers, Yaroslav FilinchukAbstract:Interaction of solid KBH4 with liquid Al(BH4)(3) at room temperature yields a solid bimetallic borohydride KAl(BH4)(4). According to the synchrotron X-ray powder diffraction, its crystal structure (space group Fddd, a = 9.7405(3), b = 12.4500(4), and c = 14.6975(4) angstrom) contains a substantially distorted tetrahedral [Al(BH4)(4)](-) anion, where the borohydride groups are coordinated to aluminum atoms via edges. The eta(2)-coordination of BH4- is confirmed by the infrared and Raman spectroscopies. The title compound is the first aluminum-based borohydride complex not stabilized by halide anions or by bulky organic cations. It is not isostructural to bimetallic chlorides, where more regular tetrahedral AlCl4- anions are present. Instead, it is isomorphic to the LT phase of TbAsO4 and can be also viewed as consisting of two interpenetrated dia-type nets where BH4 ligand is bridging Al and K cations. Variable temperature X-ray powder diffraction, TGA, DSC, and TGA-MS data reveal a single step of decomposition at 160 degrees C, with an evolution of hydrogen and some amount of diborane. Aluminum borohydride is not released in significant amounts; however, some crystalline KBH4 forms upon decomposition. The higher decomposition temperature than in chloride-substituted Li-Al (70 degrees C) and Na-Al (90 degrees C) Borohydrides suggests that the larger alkali metal cations (weaker Pearson acids) stabilize the weak Pearson base, [Al(BH4)(4)](-).
Ping Chen - One of the best experts on this subject based on the ideXlab platform.
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Amides and Borohydrides for high-capacity solid-state hydrogen storage—materials design and kinetic improvements
Mrs Bulletin, 2013Co-Authors: Jianhui Wang, Haiwen Li, Ping ChenAbstract:The development of safe, efficient, and economic hydrogen storage technologies is key for implementation of a hydrogen-based energy economy. In the search for high-hydrogen content materials, attention in the past decade has shifted to amides and Borohydrides, two representative solid-state chemical sorption materials with high hydrogen capacities that had not been previously explored for hydrogen storage. A large number of new amide and borohydride systems have recently been developed that expand the material scope for hydrogen storage. This article reviews the current progress in amides and Borohydrides with emphases on material design and kinetic improvement.
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amides and Borohydrides for high capacity solid state hydrogen storage materials design and kinetic improvements
Mrs Bulletin, 2013Co-Authors: Jianhui Wang, Haiwen Li, Ping ChenAbstract:The development of safe, efficient, and economic hydrogen storage technologies is key for implementation of a hydrogen-based energy economy. In the search for high-hydrogen content materials, attention in the past decade has shifted to amides and Borohydrides, two representative solid-state chemical sorption materials with high hydrogen capacities that had not been previously explored for hydrogen storage. A large number of new amide and borohydride systems have recently been developed that expand the material scope for hydrogen storage. This article reviews the current progress in amides and Borohydrides with emphases on material design and kinetic improvement.
Elsa Roedern - One of the best experts on this subject based on the ideXlab platform.
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effect of eutectic melting reactive hydride composites and nanoconfinement on decomposition and reversibility of libh4 kbh4
Journal of Physical Chemistry C, 2015Co-Authors: Elsa Roedern, Bjarne R. S. Hansen, Torben R JensenAbstract:Eutectic melting, reactive hydride composites, and nanoconfinement have the potential to improve the reversible hydrogen storage properties in metal Borohydrides. We study and compare the combined effect of all three methods on reversible hydrogen release and uptake of the eutectic melting lithium potassium borohydride system, 0.725LiBH4–0.275KBH4, with low melting temperature (Tm = 105 °C). The eutectic mixture and reactive hydride composites of the eutectic mixture with Mg or MgH2 are melt infiltrated into a CO2 activated nanoporous carbon scaffold, and their properties are compared to those of bulk samples. The decomposition of 0.725LiBH4–0.275KBH4 and the reactive hydride composites initiates simultaneously with the melting at 105 °C, but the decomposition remains slow until higher temperatures are reached (T > 300 °C). Eutectic melting appears to improve kinetics of hydrogen release and absorption, while nanoconfinement lowers the main hydrogen release temperature in the first cycle by up to 200 °C. ...
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Melting Behavior and Thermolysis of NaBH4−Mg(BH4)2 and NaBH4−Ca(BH4)2 Composites
Energies, 2015Co-Authors: Elsa Roedern, Peter Thygesen, Torben JensenAbstract:The physical properties and the hydrogen release of NaBH4–Mg(BH4)2 and NaBH4−Ca(BH4)2 composites are investigated using in situ synchrotron radiation powder X-ray diffraction, thermal analysis and temperature programmed photographic analysis. The composite, xNaBH4–(1 − x)Mg(BH4)2, x = 0.4 to 0.5, shows melting/frothing between 205 and 220 °C. However, the sample does not become a transparent molten phase. This behavior is similar to other alkali-alkaline earth metal borohydride composites. In the xNaBH4–(1 − x)Ca(BH4)2 system, eutectic melting is not observed. Interestingly, eutectic melting in metal Borohydrides systems leads to partial thermolysis and hydrogen release at lower temperatures and the control of sample melting may open new routes for obtaining high-capacity hydrogen storage materials
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Melting Behavior and Thermolysis of NaBH 4 −Mg(BH 4 ) 2 and NaBH 4 −Ca(BH 4 ) 2 Composites
Energies, 2015Co-Authors: Elsa Roedern, Peter Thygesen, Torben R JensenAbstract:The physical properties and the hydrogen release of NaBH 4 –Mg(BH 4 ) 2 and NaBH 4 −Ca(BH 4 ) 2 composites are investigated using in situ synchrotron radiation powder X-ray diffraction, thermal analysis and temperature programmed photographic analysis. The composite, x NaBH 4 –(1 − x )Mg(BH 4 ) 2 , x = 0.4 to 0.5, shows melting/frothing between 205 and 220 °C. However, the sample does not become a transparent molten phase. This behavior is similar to other alkali-alkaline earth metal borohydride composites. In the x NaBH 4 –(1 − x )Ca(BH 4 ) 2 system, eutectic melting is not observed. Interestingly, eutectic melting in metal Borohydrides systems leads to partial thermolysis and hydrogen release at lower temperatures and the control of sample melting may open new routes for obtaining high-capacity hydrogen storage materials.
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eutectic melting of libh4 kbh4
Physical Chemistry Chemical Physics, 2014Co-Authors: Elsa Roedern, Torben R JensenAbstract:Eutectic melting in mixtures of alkali and alkali earth metal Borohydrides can pave the way for new applications as fast ionic conductors, and facilitate hydrogen release by low temperature chemical reactions and convenient nanoconfinement. Here, we determine the eutectic composition for the lithium potassium borohydride system, 0.725LiBH4–0.275KBH4, with the lowest melting point, Tmelt ∼105 °C, of all known alkali and alkali earth metal borohydride mixtures. Mechanochemistry and manual mixing of LiBH4–KBH4 mixtures facilitate the formation of LiK(BH4)2. However, the melting or heat treatments used in this work do not produce LiK(BH4)2. The bimetallic borohydride dissociates into the monometallic Borohydrides at ∼95 °C and partial melting occurs at ∼105 °C. Analysis of the unit cell volumes of LiBH4, KBH4 and LiK(BH4)2 in the temperature range 25 to 90 °C indicates that the formation of the bimetallic borohydride is facilitated by a more dense packing as compared to the reactants. Thus, LiK(BH4)2 is considered metastable and the formation is pressure induced. A phase diagram for the LiBH4–KBH4 system is established, which illustrates the low eutectic melting point and the stability range for the bimetallic borohydride, LiK(BH4)2.
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eutectic melting of libh4 kbh4
Physical Chemistry Chemical Physics, 2014Co-Authors: Elsa Roedern, Torben R JensenAbstract:Eutectic melting in mixtures of alkali and alkali earth metal Borohydrides can pave the way for new applications as fast ionic conductors, and facilitate hydrogen release by low temperature chemical reactions and convenient nanoconfinement. Here, we determine the eutectic composition for the lithium potassium borohydride system, 0.725LiBH4–0.275KBH4, with the lowest melting point, Tmelt ∼105 °C, of all known alkali and alkali earth metal borohydride mixtures. Mechanochemistry and manual mixing of LiBH4–KBH4 mixtures facilitate the formation of LiK(BH4)2. However, the melting or heat treatments used in this work do not produce LiK(BH4)2. The bimetallic borohydride dissociates into the monometallic Borohydrides at ∼95 °C and partial melting occurs at ∼105 °C. Analysis of the unit cell volumes of LiBH4, KBH4 and LiK(BH4)2 in the temperature range 25 to 90 °C indicates that the formation of the bimetallic borohydride is facilitated by a more dense packing as compared to the reactants. Thus, LiK(BH4)2 is considered metastable and the formation is pressure induced. A phase diagram for the LiBH4–KBH4 system is established, which illustrates the low eutectic melting point and the stability range for the bimetallic borohydride, LiK(BH4)2.
Mark Paskevicius - One of the best experts on this subject based on the ideXlab platform.
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From Metal Hydrides to Metal Borohydrides.
Inorganic chemistry, 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′-...
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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, Radovan Černý, Pascal Schouwink, Lars H. Jepsen, Dorthe Bomholdt Ravnsbæk, Yaroslav Filinchuk, Martin Dornheim, Flemming Besenbacher, 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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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.