Li2(NH2BH3)(BH4)/LiNH2BH3: The first metal amidoborane borohydride complex with inseparable amidoborane precursor for hydrogen storage

Luo, Junhong; Wu, Hui; Zhou, Wei; Kang, Xiangdong; Wang, Ping

doi:10.1016/j.ijhydene.2012.10.055

Cited by 11 publications

(3 citation statements)

References 48 publications

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“…This improves the decomposition temperature to ∼90 °C for Li- or NaNH 2 BH 3 , giving way to a large family of materials. Ammonia borane metal-containing derivatives (MABs) M(NH 2 BH 3 ) n ( n = 1, M = Li + or Na + ; n = 2, M = Ca 2+ or Mg 2+ ), − including bimetallic NaLi(NH 2 BH 3 ) 2 and Na 2 Mg(NH 2 BH 3 ) 4 and mixed-anion Li 2 (NH 2 BH 3 )(BH 4 )/LiNH 2 BH 3 , were obtained in recent years. − All the listed MABs release hydrogen as well as toxic ammonia and traces of NH 2 BH 2 . For the mixed MAB–AB complex LiNH 2 BH 3 ·NH 3 BH 3 , the hydrogen release was reported to be occur to 14.0 wt % in a stepwise manner at 80 and 140 °C, and neither borazine nor aminoborane was detected .…”

Section: Introductionmentioning

confidence: 99%

Mild Dehydrogenation of Ammonia Borane Complexed with Aluminum Borohydride

et al. 2015

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Ammonia borane is a promising hydrogen store. However, its dehydrogenation is stepwise, nonreversible, and accompanied by formation of undesirable byproducts. We report on a new Al(BH4)3·NH3BH3 complex containing 17.7 wt % hydrogen, which undergoes a two-step thermal decomposition below 100 °C. The combination of volumetric, gravimetric, crystallographic, and nuclear magnetic resonance studies shows that both in the solid state and in toluene solutions, the Al-coordinated NH3BH3 already releases two H2 molecules per Al at 70 °C. Contrary to that of the pristine ammonia borane, this process is endothermic, suggesting a possibility for direct rehydrogenation. The dehydrogenation of Al(BH4)3·NH3BH3 contrasts with the complete destruction of alkali and alkaline earth metal borohydride complexes with ammonia borane in the first decomposition step. Other Al-based Lewis acids, less challenging with respect to the stability and safety than Al(BH4)3, may be good agents for supporting the reversible dehydrogenation of NH3BH3 under mild conditions.

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Section: Introductionmentioning

confidence: 99%

Mild Dehydrogenation of Ammonia Borane Complexed with Aluminum Borohydride

et al. 2015

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“…The amine–boranes (R 1 x NH (3‑ x ) BH (3‑ y ) R 2 y , where x , y ≤ 3) are well-known as hydroborating agents and selective reducing agents (for example, chiral amine–borane complexes can be used in enantioselective syntheses). − These compounds find many interesting applications − and are considered as prospective materials for reversible hydrogen storage systems due to their high H 2 volumetric and gravimetric density. − Amine–boranes and related bifunctional compounds (metal borohydride ammonia borane complexes, metal tetrahydroborate ammoniates, − metal amidoborane borohydrides, , amidoborane ammoniates, metal hydrazine–boranes, , etc.) containing both acidic and basic groups are of particular interest for these purposes, as these compounds are capable to evolve hydrogen at heating .…”

Section: Introductionmentioning

confidence: 99%

Dihydrogen Bond Intermediated Alcoholysis of Dimethylamine–Borane in Nonaqueous Media

et al. 2015

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Dimethylamine-borane (DMAB) acid/base properties, its dihydrogen-bonded (DHB) complexes and proton transfer reaction in nonaqueous media were investigated both experimentally (IR, UV/vis, NMR, and X-ray) and theoretically (DFT, NBO, QTAIM, and NCI). The effects of DMAB concentration, solvents polarity and temperature on the degree of DMAB self-association are shown and the enthalpy of association is determined experimentally for the first time (-ΔH°assoc = 1.5-2.3 kcal/mol). The first case of "improper" (blue-shifting) NH···F hydrogen bonds was observed in fluorobenzene and perfluorobenzene solutions. It was shown that hydrogen-bonded complexes are the intermediates of proton transfer from alcohols and phenols to DMAB. The reaction mechanism was examined computationally taking into account the coordinating properties of the reaction media. The values of the rate constants of proton transfer from HFIP to DMAB in acetone were determined experimentally [(7.9 ± 0.1) × 10(-4) to (1.6 ± 0.1) × 10(-3) mol(-1)·s(-1)] at 270-310 K. Computed activation barrier of this reaction ΔG(‡theor)298 K(acetone) = 23.8 kcal/mol is in good agreement with the experimental value of the activation free energy ΔG(‡exp)270 K = 21.1 kcal/mol.

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“…Here, it is not expected that the intrinsic chemical reactivity between AB and Mg can be changed by varying their respective quantities. On the other hand, the dehydrogenation behaviors of many AB-related samples were found to show high dependence on heating. ,,− Hence, the effect of composition variation on determining the dehydrogenation pathways might be attributed to its effect on affecting heat transfer within the sample, given the fact that Mg is a good heat conductor while AB is not (i.e., the thermal conductivities of AB and Mg are 15 W/m-K and 156 W/m-K, respectively). To test this speculation, we added some fine Al powder, which possesses a thermal conductivity comparable to that of Mg (i.e., κ Al = 205 W/m-K) but cannot react with AB, to the 2AB/0.5Mg sample to constitute a new composite with the molar ratio of AB:Mg:Al being 2:0.5:0.1.…”

Section: Results and Discussionmentioning

confidence: 99%

Rapidly Releasing over 9 wt % of H₂ from NH₃BH₃–Mg or NH₃BH₃–MgH₂ Composites around 85 °C

et al. 2016

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It is ideal that the hydrogen storage materials for vehicular applications can desorb substantial amounts of hydrogen below 85 °C, the operating temperature of polymer electrolyte membrane (PEM) fuel cells. Ammonia borane (NH3BH3, AB for short), because of its intriguingly high hydrogen density (i.e., 19.6 wt %) and moderate thermal stability, is widely regarded as a promising on-board hydrogen storage medium. However, at this temperature, both its dehydrogenation kinetics and deliverable H-capacity are far from meeting the requirements for practical applications. Here, we report that the Mg- or MgH2-modified AB can deliver over 9 wt % of H2 within 1.5 h at approximately 85 °C. Such pronounced dehydrogenation properties are found to be enabled by the combination of three factors, including partial phase transition of normal AB to its mobile phase AB* in the starting material, adequate sample thermal conductivity, and sufficiently intensive external energy input. A further mechanistic study indicates that the dehydrogenation of the AB–Mg or AB–MgH2 sample should likely involve a three-step mechanism, with the formation of a metastable or even unstable magnesium amidoborane phase being a central event.

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Li2(NH2BH3)(BH4)/LiNH2BH3: The first metal amidoborane borohydride complex with inseparable amidoborane precursor for hydrogen storage

Cited by 11 publications

References 48 publications

Mild Dehydrogenation of Ammonia Borane Complexed with Aluminum Borohydride

Mild Dehydrogenation of Ammonia Borane Complexed with Aluminum Borohydride

Dihydrogen Bond Intermediated Alcoholysis of Dimethylamine–Borane in Nonaqueous Media

Rapidly Releasing over 9 wt % of H₂ from NH₃BH₃–Mg or NH₃BH₃–MgH₂ Composites around 85 °C

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Li2(NH2BH3)(BH4)/LiNH2BH3: The first metal amidoborane borohydride complex with inseparable amidoborane precursor for hydrogen storage

Cited by 11 publications

References 48 publications

Mild Dehydrogenation of Ammonia Borane Complexed with Aluminum Borohydride

Mild Dehydrogenation of Ammonia Borane Complexed with Aluminum Borohydride

Dihydrogen Bond Intermediated Alcoholysis of Dimethylamine–Borane in Nonaqueous Media

Rapidly Releasing over 9 wt % of H2 from NH3BH3–Mg or NH3BH3–MgH2 Composites around 85 °C

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Rapidly Releasing over 9 wt % of H₂ from NH₃BH₃–Mg or NH₃BH₃–MgH₂ Composites around 85 °C