Structural evolution of ammonia borane for hydrogen storage

Yang, Junzhi; Lamsal, Jagat; Cai, Q.; James, William Joseph; Yelon, W. B.

doi:10.1063/1.2889535

Cited by 57 publications

(80 citation statements)

References 15 publications

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“…The transition is characterized by first-order rotational order-disorder associated to substantial increase of the entropy [20]. The cell dimensions ( Figure 2 and Table 1) are also consistent with previous reports [12,18,19]. The orthorhombic phase shows a negative coefficient of thermal expansion for a, and a positive coefficient for both b; the c cell dimension remains virtually unchanged.…”

Section: Ammonia Borane Absupporting

confidence: 78%

“…Elsewhere it was suggested that this polymorphic transition is quite close to a second order, as follows from almost gradual evolution of the cell dimensions [19]. The transition temperature of 205 K in our conditions is lower by 15-20 K of that reported in previous works [12,18,19]. This may be related to the nature and synthesis procedure of the borane: ours was lab-prepared and it was of high purity (>99%), whereas those in references [12,18,19] were commercial and with lower purity.…”

Section: Ammonia Borane Abcontrasting

confidence: 44%

“…The transition temperature of 205 K in our conditions is lower by 15-20 K of that reported in previous works [12,18,19]. This may be related to the nature and synthesis procedure of the borane: ours was lab-prepared and it was of high purity (>99%), whereas those in references [12,18,19] were commercial and with lower purity. The transition occurs between the low-temperature orthorhombic phase (s.g. Pmn2 1 , Figure S2) to the high-temperature tetragonal phase (s.g. I4mm, Figure S3).…”

Section: Ammonia Borane Abcontrasting

confidence: 40%

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In situ Synchrotron X-ray Thermodiffraction of Boranes

2016

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Abstract:Boranes of low molecular weight are crystalline materials that have been much investigated over the past decade in the field of chemical hydrogen storage. In the present work, six of them have been selected to be studied by in situ synchrotron X-ray thermodiffraction. The selected boranes are ammonia borane NH 3 BH 3 (AB), hydrazine borane N 2 H 4 BH 3 (HB), hydrazine bisborane N 2 H 4 (BH 3 ) 2 (HBB), lithium LiN 2 H 3 BH 3 (LiHB) and sodium NaN 2 H 3 BH 3 (NaHB) hydrazinidoboranes, and sodium triborane NaB 3 H 8 (STB). They are first investigated separately over a wide range of temperature (80-300 K), and subsequently compared. Differences in crystal structures, the existence of phase transition, evolutions of unit cell parameters and volumes, and variation of coefficients of thermal expansion can be observed. With respect to AB, HB and HBB, the differences are mainly explained in terms of molecule size, conformation and motion (degree of freedom) of the chemical groups (NH 3 , N 2 H 4 , BH 3 ). With respect to LiHB, NaHB and STB, the differences are explained by a stabilization effect favored by the alkali cations via M¨¨¨H interactions with four to five borane anions. The main results are presented and discussed herein.

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Section: Ammonia Borane Absupporting

confidence: 78%

Section: Ammonia Borane Abcontrasting

confidence: 44%

Section: Ammonia Borane Abcontrasting

confidence: 40%

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In situ Synchrotron X-ray Thermodiffraction of Boranes

2016

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“…Therefore two methyl groups have different chemical shift on phenyl ring moiety where N1 atom was deuterated (1bA form). Nonequivalency of the chemical shifts of two methyl groups on 1bA corresponds to the slightly restriction of the rotation [41] and caused to increasing the rotational barrier of tetrazole ring around C5-O1 and also O1-C6 bonds (ether linkage bond). In 13 C NMR spectrum of 1b, before adding D 2 O, the chemical shifts of two methyl groups are equivalent at δ 16.07 ppm while after adding D 2 O, the chemical shifts of those methyl groups are slightly nonequivalent (at δ 15.98 ppm and has a shoulder in the peak's right side; Fig.…”

Section: Resultsmentioning

confidence: 98%

Isotopic effect on tautomeric behavior of 5‐(2,6‐disubstituted‐aryloxy)‐tetrazoles

Pesyan

2011

Magnetic Reson in Chemistry

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Isotopic effect on tautomeric behaviors of the synthesized 5-phenoxy- (1a), 5-(2,6-dimethylphenoxy)-(1b), 5-(2,6-diisopropylphenoxy)-(1c), 5-(2,6-dimethoxyphenoxy)-(1d) and 5-(4-methylphenoxy)-tetrazole (1e) were investigated in DMSO-d6 by adding one drop of D2O. Among 1a-e, 1a, 1d and 1e show small rotational barrier around C5-O1 and O1-C6 while in 1b and 1c there are distinguishable rotational barrier about that bonds. The (1)H NMR spectra of 1b and 1c show slightly different chemical shifts for two methyl and isopropyl groups on those phenyl ring, respectively, while the chemical shifts difference (Δδ) between two methyl and two isopropyl groups were enhanced by adding D2O. The (13)C NMR spectra of 1b show two overlapped singlets for methyl groups after adding D2O. Representatively, the calculations of compound 1c were performed with GAUSSIAN-03 and the rotational barrier about C5-O1 and between isopropyl group and phenyl ring in 1c was calculated with B3LYP/6-31G(d) basis set.

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“…However, they were not able to determine the hydrogen atom positions in the structure. Sorokin et al [78] claimed in 1963 a face-centered orthorhombic structure for this phase, but all later studies confirmed the tetragonal structure [62,63,76,[79][80][81].…”

Section: Phase Imentioning

confidence: 73%

Ammonia borane at high pressures

et al. 2014

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Ammonia borane has received tremendous research attention in the past decade because of its potential for chemical hydrogen storage. This paper reviews recent studies about the behavior of ammonia borane at high pressures. While much work is still needed to comprehensively understand the pressure influence on this molecular crystal, a phase diagram based on the available experimental and theoretical data is constructed. Raman spectroscopy studies indicate five transitions upon compression up to 65 GPa at ambient temperature. Diffraction experiments and theoretical studies demonstrate that three of these transitions are first-order phase transformations in the sequence of I4mm-Cmc2 1 -P2 1 -(different) P2 1 , and two are iso-structural. A low-temperature phase (Pmn2 1 ) and a high-temperature high-pressure phase (Pmna) are also recognized.

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Structural evolution of ammonia borane for hydrogen storage

Cited by 57 publications

References 15 publications

In situ Synchrotron X-ray Thermodiffraction of Boranes

In situ Synchrotron X-ray Thermodiffraction of Boranes

Isotopic effect on tautomeric behavior of 5‐(2,6‐disubstituted‐aryloxy)‐tetrazoles

Ammonia borane at high pressures

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