Thermodynamical stabilities of metal-borohydrides

Nakamori, Yoshiteru; Li, Haiwen; Kikuchi, Kentaro; Aoki, Masakazu; Miwa, Kenji; Towata, Shin‐ichi; Orimo, Shin Ichi

doi:10.1016/j.jallcom.2007.03.144

Cited by 136 publications

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“…4(a and b), i.e. 393 and 334 K, respectively; but impurity gases of diborane, were released along with the desorption of hydrogen (not shown) [18,19]. On the other hand, the thermal desorption profiles of the samples with the compositions of ZnLi(BH 4 ) 3 and AlLi(BH 4 ) 4 indicate that both The relationship between T d and the averaged value of χ P of ZrLi m−4 is expressed in Fig.…”

Section: Methodsmentioning

confidence: 99%

“…Metal borohydrides (M(BH 4 ) n ), such as LiBH 4 and Mg(BH 4 ) 2 [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] have been attracting great interest as one of the potential candidates of advanced hydrogen storage materials, because of their high gravimetric hydrogen densities.…”

Section: Introductionmentioning

confidence: 99%

“…Among them, borohydrides composed of metals with larger χ P , such as Zn (χ P = 1.6), Al (χ P = 1.5) and Zr (χ P = 1.4), are reported to have lower T d , i.e. 398 [17,18], 334 [19] and 440 K [17], respectively. However, Zn(BH 4 ) 2 and Al(BH 4 ) 3 are so unstable that diborane as an impurity gas is released along with hydrogen desorption on heating [18,19]; while Zr(BH 4 ) 4 evaporates easily due to its low melting point.…”

Section: Introductionmentioning

confidence: 99%

“…398 [17,18], 334 [19] and 440 K [17], respectively. However, Zn(BH 4 ) 2 and Al(BH 4 ) 3 are so unstable that diborane as an impurity gas is released along with hydrogen desorption on heating [18,19]; while Zr(BH 4 ) 4 evaporates easily due to its low melting point. On the other hand, LiBH 4 with the smaller χ P of Li is so stable that its T d is approximately as high as 740 K. Therefore, their thermal stabilities are expected to be , examined by gas chromatography and quadrupole mass spectroscopy, respectively.…”

Section: Introductionmentioning

confidence: 99%

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Materials designing of metal borohydrides: Viewpoints from thermodynamical stabilities

Orimo

Nakamori

et al. 2007

Journal of Alloys and Compounds

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Double-cation borohydrides MLi m−n (BH 4 ) m (M = Zn, n = 2; M = Al, n = 3; M = Zr, n = 4; n ≤ m) were expected to be synthesized and their thermodynamical stabilities were also examined experimentally. The samples with the compositions of ZnLi(BH 4 ) 3 and AlLi(BH 4 ) 4 disproportionate into Zn(BH 4 ) 2 -(or Al(BH 4 ) 3 -) and LiBH 4 -based phases upon heating, respectively. However, no disproportionation reaction is observed in ZrLi m−4 (BH 4 ) m (m = 5 and 6). It should be emphasized that hydrogen desorption temperature T d of ZrLi m−4 (BH 4 ) m continuously increases from 440 to 650 K as the composition m increases from 4 to 6, and approaches to 740 K (T d of LiBH 4 ). The experimental results indicate that the combination of appropriate cations is an effective method to adjust the thermodynamical stabilities of metal borohydrides, similar to the conventional "alloying" method for hydrogen storage alloys.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Materials designing of metal borohydrides: Viewpoints from thermodynamical stabilities

Orimo

Nakamori

et al. 2007

Journal of Alloys and Compounds

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“…40,41 Specifically, the dehydrogenation temperature of M(BH 4 Figure 9, revealed similar peak characteristics for these two samples.…”

Section: Synthesis Of Magnesium Borohydride Hydrazinatesmentioning

confidence: 68%

Sodium borohydride hydrazinates: synthesis, crystal structures, and thermal decomposition behavior

Mao

Guo

et al. 2015

J. Mater. Chem. A

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. (2015). Sodium borohydride hydrazinates: synthesis, crystal structures, and thermal decomposition behavior. Journal of Materials Chemistry A, 3 (21), 11269-11276. Sodium borohydride hydrazinates: synthesis, crystal structures, and thermal decomposition behavior AbstractMetallic borohydride hydrazinates are novel boron-and nitrogen-based materials that appear to be promising candidates for chemical hydrogen storage. Herein, sodium borohydride hydrazinates, including NaBH 4 ·N2H 4 and NaBH 4 ·2N 2 H 4 , were synthesized via a facile solution synthesis approach based on the solid-liquid reaction between NaBH 4 and hydrazine in tetrahydrofuran (THF) solution. The crystal structure of NaBH 4 ·2N 2 H 4 was solved to a monoclinic structure with unit cell parameters a = 8.4592(2) Å, b = 11.7131(2) Å, c = 6.4584(1) Å, and β = 100.0777(14)°, with space group A1a1 (9). Each Na + ion interacts with four neighboring N 2 H 4 molecules, leading to the formation of Na 4 [N 2 H 4 ] 4 4+ cationic chains along the a direction. Such cationic chains are surrounded by BH 4 − anions. The NaBH 4 ·xN 2 H 4 (x = 1, 2) was characterized by Powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), and mass spectroscopy (MS) to obtain a full picture of the relationship of the structure to the decomposition, which will be useful for future work on borohydride hydrazinates or the study of other B-N materials. Furthermore, magnesium borohydride hydrazinates were synthesized by ball milling the sodium borohydride hydrazinates with magnesium borohydride, and their thermal decomposition was investigated as well. differential scanning calorimetry (DSC), and mass spectroscopy (MS) to obtain a full picture of the relationship of the structure to the decomposition, which will be useful for future work on borohydride hydrazinates or the study of other B-N materials.Furthermore, magnesium borohydride hydrazinates were synthesized by ball milling the sodium borohydride hydrazinates with magnesium borohydride, and their thermal decomposition was investigated as well.

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Complex Hydrides

and

Felderhoff

2010

Handbook of Hydrogen Storage

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Complex hydrides are salt-like materials in which hydrogen is covalently bound to the central atoms, in this way a crystal structure consisting of so-called complex anions is formed. In general, complex hydrides have the chemical formula A x Me y H z . Compounds where position A is preferentially occupied by elements of the first and second groups of the periodic table and Me is occupied either by boron or aluminum are well known and have been intensively investigated. However, another possibility is that complex hydrides are built by transition metal cations. Complex metal hydrides have been known for more than 50 years, but for many years they were not considered for reversible hydrogen storage due to the high kinetic barriers of the decomposition requiring high temperatures. The situation changed in 1997 when Bogdanovi c and Schwickardi discovered that the kinetic barrier of the decomposition of the complex metal hydride, NaAlH 4 , can be lowered by the addition of Ti catalysts and that the material becomes reversible close to acceptable technical conditions [1]. They further showed not only that catalysts can enhance the kinetics of dehydrogenation but also that rehydrogenation under moderate conditions becomes feasible. This breakthrough induced the publication of a tremendous number of papers focusing on the synthesis and the properties of complex hydrides. The major goal is to understand the basic steps of dehydrogenation and rehydrogenation and the role of catalysts. Many complex metal hydrides have high hydrogen gravimetric storage capacities and some of them are commercially available. Some complex hydride systems, such as Mg 2 FeH 6 and Al(BH 4 ) 3 , have an extremely high volumetric hydrogen density of up to 150 kg m À3 . Compared to liquid hydrogen with a volumetric density of 70 kg m À3 , the amount of hydrogen in such metal hydrides is much higher. This makes complex transition metal hydrides interesting as potential storage materials.Handbook of Hydrogen Storage. Edited by Michael Hirscher

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Thermodynamical stabilities of metal-borohydrides

Cited by 136 publications

References 20 publications

Materials designing of metal borohydrides: Viewpoints from thermodynamical stabilities

Materials designing of metal borohydrides: Viewpoints from thermodynamical stabilities

Sodium borohydride hydrazinates: synthesis, crystal structures, and thermal decomposition behavior

Complex Hydrides

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