Structure and dynamics of ammonium borohydride

Flacau, Roxana; Ratcliffe, Christopher I.; Desgreniers, Serge; Yao, Yansun; Klug, D. D.; Pallister, Peter J.; Moudrakovski, Igor L.; Ripmeester, John A.

doi:10.1039/c0cc03297b

Cited by 19 publications

(32 citation statements)

References 26 publications

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“…An important difference for the former case is the presence of the short dihydrogen (N)H σ+ ⋅⋅⋅H σ− (B) bonds (Figure ). The experimental H⋅⋅⋅H distance of 1.82 Å is confirmed by the DFT calculations (Table S1 in the Supporting Information) and found to be significantly shorter than those in NH 3 BH 3 (1.91(5) Å) and in NH 4 BH 4 (2.28 Å) …”

Section: Resultsmentioning

confidence: 99%

“…The experimental H···H distance of 1.82 is confirmed by the DFT calculations (Table S1 in the Supporting Information)a nd found to be significantly shorter than those in NH 3 BH 3 (1.91 (5) ) [38] and in NH 4 BH 4 (2.28 ). [39] The high-temperature polymorph of Cs[Al(BH 4 ) 4 ]c rystallizes in the tetragonal space group I4 1 /amd. Its crystal structure is derived from the scheelite type, [40] which is also the prototype of another mixed-cation borohydride Cs[Y(BH 4 ) 4 ].…”

Section: Crystal Structures Of the Mixed-cation Aluminum Borohydridesmentioning

confidence: 99%

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Solid Aluminum Borohydrides for Prospective Hydrogen Storage

et al. 2017

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Metal borohydrides are intensively researched as high-capacity hydrogen storage materials. Aluminum is a cheap, light, and abundant element and Al can serve as a template for reversible dehydrogenation. However, Al(BH ) , 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(BH ) ], which are all solid under ambient conditions, show diverse thermal decomposition behaviors: Al(BH ) is released for M=Li or Na , whereas heavier derivatives evolve hydrogen and diborane. NH [Al(BH ) ], containing both protic and hydridic hydrogen, has the lowest decomposition temperature of 35 °C and yields Al(BH ) ⋅NHBH and hydrogen. The decomposition temperatures, correlated with the cations' ionic potential, show that M[Al(BH ) ] 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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Section: Resultsmentioning

confidence: 99%

Section: Crystal Structures Of the Mixed-cation Aluminum Borohydridesmentioning

confidence: 99%

Solid Aluminum Borohydrides for Prospective Hydrogen Storage

et al. 2017

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“…Powder x-ray diffraction measurements at 100 K indicated that NH 4 BH 4 exhibits a cubic crystal structure (space group F m-3m) with the two tetrahedral complex ions, ammonium (NH + 4 ) and borohydride (BH − 4 ), which may be described as cubes with half occupancies of hydrogen due to disorder (see Supplemental Material (SM), Fig. S1 [5]) [3,6]. Variabletemperature neutron powder diffraction measurements on the deuterated equivalent ND 4 BD 4 showed that, at 5 K, ND 4 BD 4 exhibits a dynamically ordered trigonal polymorph (P-3), which transforms to a rhombohedral polymorph (R-3m) at 45 K, which in turn transforms to the cubic high-temperature polymorph (F m-3m) at 60 K [7].…”

Section: Introductionmentioning

confidence: 99%

Interplay of NH4+ and BH4− reorientational dynamics in NH4BH
Andersson
¹
,
Grinderslev
²
,
Jensen
³

et al. 2020
Phys. Rev. Materials
11
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The reorientational dynamics of ammonium borohydride (NH 4 BH 4) was studied using quasielastic neutron scattering in the temperature interval from 10 to 240 K, which covers both the dynamically ordered and disordered polymorphs of NH 4 BH 4. In the low-temperature (< 50 K) ordered polymorph of NH 4 BH 4 , analysis of the quasielastic neutron scattering data reveals that no reorientational dynamics is present within the probed timescale region of 0.1 to 100 ps. In the high-temperature (> 50 K) disordered polymorph, the analysis establishes the onset of NH + 4 and BH − 4 dynamics at around 50 and 125 K, respectively. The relaxation time at 150 K for NH + 4 is approximately 1 ps, while around 100 ps for BH − 4. The NH + 4 dynamics at temperatures below 125 K is associated with preferential tetrahedral tumbling motions, where each of the hydrogen atoms in the NH + 4 tetrahedron can visit any of the four hydrogen sites, however, reorientations around a specific axis are more frequently occurring (C 2 or C 3). At higher temperatures, the analysis does not exclude a possible evolution of the NH + 4 dynamics from tetrahedral tumbling to either cubic tumbling, where the hydrogen atoms can visit any of the eight positions corresponding to the corners of a cube, or isotropic rotational diffusion, where the hydrogen atoms can visit any location on the surface of a sphere. The BH − 4 dynamics can be described as cubic tumbling. The difference in reorientational dynamics between the two ions is related to the difference of the local environment where the dynamically much slower BH − 4 anion imposes a noncubic environment on the NH + 4 cation.

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“…Aside from ammonium borohydride NH4BH4 itself [5][6][7], the ammonium cation has been rather neglected by the hydrogen storage community, and so far considered only in conjunction with higher boranes such as NH4B3H8 [8], (NH4)2B10H10 or (NH4)2B12H12 [9] which impede the borazine evolution during thermolysis thanks to their stable borane cages, but never as a building block in a metal-based material. Attempts to tailor the thermal stability of NH4BH4, which decomposes slowly at room temperature (RT), have also been carried out to develop it as solid state hydrogen storage material [7,10].…”

Section: Introductionmentioning

confidence: 99%

“…Attempts to tailor the thermal stability of NH4BH4, which decomposes slowly at room temperature (RT), have also been carried out to develop it as solid state hydrogen storage material [7,10].…”

Section: Introductionmentioning

confidence: 99%

Increasing Hydrogen Density with the Cation-Anion Pair BH4−-NH4+ in Perovskite-Type NH4Ca(BH4)3

et al. 2015

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A novel metal borohydride ammonia-borane complex Ca(BH4)2·NH3BH3 is characterized as the decomposition product of the recently reported perovskite-type metal borohydride NH4Ca(BH4)3, suggesting that ammonium-based metal borohydrides release hydrogen gas via ammonia-borane-complexes. For the first time the concept of proton-hydride interactions to promote hydrogen release is applied to a cation-anion pair in a complex metal hydride. NH4Ca(BH4)3 is prepared mechanochemically from Ca(BH4)2 and NH4Cl as well as NH4BH4 following two different protocols, where the synthesis procedures are modified in the latter to solvent-based ball-milling using diethyl ether to maximize the phase yield in chlorine-free samples. During decomposition of NH4Ca(BH4)3 pure H2 is released, prior to the decomposition of the complex to its constituents. As opposed to a previously reported adduct between Ca(BH4)2 and NH3BH3, the present complex is described as NH3BH3-stuffed α-Ca(BH4)2.

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Structure and dynamics of ammonium borohydride

Cited by 19 publications

References 26 publications

Solid Aluminum Borohydrides for Prospective Hydrogen Storage

Solid Aluminum Borohydrides for Prospective Hydrogen Storage

Interplay of NH4+ and BH4− reorientational dynamics in NH4BH
Andersson
¹
,
Grinderslev
²
,
Jensen
³

et al. 2020
Phys. Rev. Materials
11
1
10
0
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Increasing Hydrogen Density with the Cation-Anion Pair BH4−-NH4+ in Perovskite-Type NH4Ca(BH4)3

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Structure and dynamics of ammonium borohydride

Cited by 19 publications

References 26 publications

Solid Aluminum Borohydrides for Prospective Hydrogen Storage

Solid Aluminum Borohydrides for Prospective Hydrogen Storage

Interplay of NH4+ and BH4− reorientational dynamics in NH4BHAndersson1, Grinderslev2, Jensen3 et al. 2020Phys. Rev. Materials111100View full textAdd to dashboardCite

Increasing Hydrogen Density with the Cation-Anion Pair BH4−-NH4+ in Perovskite-Type NH4Ca(BH4)3

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Interplay of NH4+ and BH4− reorientational dynamics in NH4BH
Andersson
¹
,
Grinderslev
²
,
Jensen
³

et al. 2020
Phys. Rev. Materials
11
1
10
0
View full text Add to dashboard Cite