Interaction between Lithium Amide and Lithium Hydride

Chen, Ping; Xiong, Zhitao; Luo, Jia; Lin, and J.; Tan, K.L.

doi:10.1021/jp034149j

Cited by 408 publications

(469 citation statements)

References 15 publications

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“…As reported in literature, the combination of H d + and H dÀ is the main driving force for the facile release of H 2 in the interaction between amide-hydride [16] and AB systems. [1] To identify the origin of the H d + that contributes to earlystage H 2 release, we selectively labeled the ammonia with 2 H by exposing unlabeled CaAB to 2 molar equiv of ND 3 .…”

Section: Dehydrogenation Mechanism Of Calcium Amidoborane Ammoniatementioning

confidence: 84%

Mechanistic Investigation on the Formation and Dehydrogenation of Calcium Amidoborane Ammoniate

Chua¹,

Wen²,

Shaw³

et al. 2012

ChemSusChem

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Possessing high H2 capacities and interesting dehydrogenation behavior, metal amidoborane ammoniates were prepared by reacting Ca(NH2)2, MgNH, and LiNH2 with ammonia borane to form Ca(NH2BH3)2⋅2 NH3, Mg(NH2BH3)2⋅NH3, and Li(NH2BH3)2⋅NH3 (LiAB⋅NH3). Insight into the mechanisms of amidoborane ammoniate formation and dehydrogenation was obtained by using isotopic labeling techniques. Selective 15N and 2H labeling showed that the formation of the ammoniate occurs via the transfer of one H(N) from ammonia borane to the [NH2]− unit in Ca(NH2)2 giving rise to NH3 and [NH2BH3]−. Supported by theoretical calculations, it is suggested that the improved dehydrogenation properties of metal amidoborane ammoniates compared to metal amidoboranes are a result of the participation of a strong dihydrogen bond between the NH3 molecule and [NH2BH3]−. Our study elucidates the reaction pathway involved in the synthesis and dehydrogenation of Ca(NH2BH3)2⋅2 NH3, and clarifies our understanding of the role of NH3, that is, it is not only involved in stabilizing the structure, but also in improving the dehydrogenation properties of metal amidoboranes.

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Section: Dehydrogenation Mechanism Of Calcium Amidoborane Ammoniatementioning

confidence: 84%

Mechanistic Investigation on the Formation and Dehydrogenation of Calcium Amidoborane Ammoniate

Chua¹,

Wen²,

Shaw³

et al. 2012

ChemSusChem

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“…4 Thermal desorption measurements carried out on a LiNH 2 +2LiD mixture, however, showed that it produces mainly H 2 in addition to HD and D 2 (instead of mainly HD as one would have expected). 4 This seems to be contrary to the redox hypothesis.…”

Section: Introductionmentioning

confidence: 92%

“…(2), it has been suggested that LiNH 2 may react directly with LiH at the LiNH 2 /LiH interface according to a polar mechanism to produce H 2 . [3][4][5] The mechanism is explained in terms of the strong affinity between protonic hydrogen (H δ+ ) in LiNH 2 and hydridic hydrogen (H δ− ) in LiH where the redox reaction of H δ+ and H δ− produces molecular hydrogen (H 2 ). 4 Thermal desorption measurements carried out on a LiNH 2 +2LiD mixture, however, showed that it produces mainly H 2 in addition to HD and D 2 (instead of mainly HD as one would have expected).…”

Section: Introductionmentioning

confidence: 99%

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Mechanisms for the decomposition and dehydrogenation of Li amide/imide

2012

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Reversible reaction involving Li amide (LiNH2) and Li imide (Li2NH) is a potential mechanism for hydrogen storage. Recent synchrotron x-ray diffraction experiments [W. I. David et al., J. Am. Chem. Soc. 129, 1594] suggest that the transformation between LiNH2 and Li2NH is a bulk reaction that occurs through non-stoichiometric processes and involves the migration of Li + and H + ions. In order to understand the atomistic mechanisms behind these processes, we carry out comprehensive first-principles studies of native point defects and defect complexes in the two compounds. We find that both LiNH2 and Li2NH are prone to Frenkel disorder on the Li sublattice. Lithium interstitials and vacancies have low formation energies and are highly mobile, and therefore play an important role in mass transport and ionic conduction. Hydrogen interstitials and vacancies, on the other hand, are responsible for forming and breaking N−H bonds, which is essential in the Li amide/imide reaction. Based on the structure, energetics, and migration of hydrogen-, lithium-, and nitrogen-related defects, we propose that LiNH2 decomposes into Li2NH and NH3 according to two competing mechanisms with different activation energies: one mechanism involves the formation of native defects in the interior of the material, the other at the surface. As a result, the prevailing mechanism and hence the effective activation energy for decomposition depend on the surface-tovolume ratio or the specific surface area, which changes with particle size during ball milling. These mechanisms also provide an explanation for the dehydrogenation of LiNH2+LiH mixtures.

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“…On the contrary, pure lithium amide and lithium hydride, separately, decompose at temperatures above 300 • C and 550 • C, respectively [3]. In the first desorption mechanism proposed, the driving force is represented by the release of hydrogen as a consequence of the direct reaction between the H + in LiNH 2 and H − in LiH to form H 2 [4]. The second desorbing mechanism involves the decomposition of LiNH 2 to 1 2 Li 2 NH and 1 2 NH 3 (Equation (1)), while, in the second step, 1 2 LiH quickly reacts with 1 …”

Section: Li-n-h Systemmentioning

confidence: 99%

Recent Progress and New Perspectives on Metal Amide and Imide Systems for Solid-State Hydrogen Storage

et al. 2018

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Hydrogen storage in the solid state represents one of the most attractive and challenging ways to supply hydrogen to a proton exchange membrane (PEM) fuel cell. Although in the last 15 years a large variety of material systems have been identified as possible candidates for storing hydrogen, further efforts have to be made in the development of systems which meet the strict targets of the Fuel Cells and Hydrogen Joint Undertaking (FCH JU) and U.S. Department of Energy (DOE). Recent projections indicate that a system possessing: (i) an ideal enthalpy in the range of 20-50 kJ/mol H 2 , to use the heat produced by PEM fuel cell for providing the energy necessary for desorption; (ii) a gravimetric hydrogen density of 5 wt. % H 2 and (iii) fast sorption kinetics below 110 • C is strongly recommended. Among the known hydrogen storage materials, amide and imide-based mixtures represent the most promising class of compounds for on-board applications; however, some barriers still have to be overcome before considering this class of material mature for real applications. In this review, the most relevant progresses made in the recent years as well as the kinetic and thermodynamic properties, experimentally measured for the most promising systems, are reported and properly discussed.

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Interaction between Lithium Amide and Lithium Hydride

Cited by 408 publications

References 15 publications

Mechanistic Investigation on the Formation and Dehydrogenation of Calcium Amidoborane Ammoniate

Mechanistic Investigation on the Formation and Dehydrogenation of Calcium Amidoborane Ammoniate

Mechanisms for the decomposition and dehydrogenation of Li amide/imide

Recent Progress and New Perspectives on Metal Amide and Imide Systems for Solid-State Hydrogen Storage

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