Reaction Intermediates during the Dehydrogenation of Metal Borohydrides: A Cluster Perspective

Li, Sa; Willis, Mary; Jena, P.

doi:10.1021/jp106638u

Cited by 33 publications

(45 citation statements)

References 28 publications

(61 reference statements)

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“…The dehydrogenation process is found to also proceed through multiple steps together with the formation of intermediate compounds [62,63,65], as summarized in Figure 2. Thus far, one of the intermediate compounds has been theoretically predicted and experimentally confirmed as being MgB 12 H 12 [28,29,62,[65][66][67][68][69][70] [62]. These differences might originate from differences in the measurement conditions.…”

Section: Fundamentals Of Hydrogen Storage Propertiesmentioning

confidence: 99%

Recent Progress in Metal Borohydrides for Hydrogen Storage

et al. 2011

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Abstract:The prerequisite for widespread use of hydrogen as an energy carrier is the development of new materials that can safely store it at high gravimetric and volumetric densities. Metal borohydrides M(BH 4 ) n (n is the valence of metal M), in particular, have high hydrogen density, and are therefore regarded as one such potential hydrogen storage material. For fuel cell vehicles, the goal for on-board storage systems is to achieve reversible store at high density but moderate temperature and hydrogen pressure. To this end, a large amount of effort has been devoted to improvements in their thermodynamic and kinetic aspects. This review provides an overview of recent research activity on various M(BH 4 ) n , with a focus on the fundamental dehydrogenation and rehydrogenation properties and on providing guidance for material design in terms of tailoring thermodynamics and promoting kinetics for hydrogen storage.

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Section: Fundamentals Of Hydrogen Storage Propertiesmentioning

confidence: 99%

Recent Progress in Metal Borohydrides for Hydrogen Storage

et al. 2011

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“…We consider for this purpose Cr[BC 5 (CN) 6 ] 2 cluster which is a 16-electron system. 30 Thus, the di-anion of Cr[BC 5 (CN) 6 ] 2 is even more stable than B 12 H 12 2À ! Note that the di-anionic Cr[BC 5 (CN) 6 ] 2 is isoelectronic with mono-anionic Mn[BC 5 (CN) 6 ] 2 whose stability, as discussed earlier, has already been established.…”

Section: àmentioning

confidence: 99%

Unusual stability of multiply charged organo-metallic complexes

et al. 2015

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Stabilization of multiply charged ions in the gas phase has been one of the most fundamental challenges in chemistry since it is hindered either because of fragmentation or auto-electron detachment. Closo-borane B 12 H 12 2À is among the best known multiply charged di-anion in chemistry where the second electron is bound by 0.9 eV. We show that transition metal based organo-metallic di-anions such as Cr[BC 5 (CN) 6 ] 2 can be even more stable than B 12 H 12 2À where the second electron is bound by 2.58 eV. This is in contrast to C 6 H 6 which is unstable even as a mono-anion. The unusual stability of the organo-metallic complex is brought about by having the added electrons simultaneously satisfy three separate electroncounting rules, namely the octet rule, the aromaticity rule, and the 18-electron rule. Mono-anionic Mn[BC 5 (CN) 6 ] 2 which is isoelectronic with di-anionic Cr[BC 5 (CN) 6 ] 2 is also found to be very stable. The design of unusually stable singly and multiply charged organo-metallic negative ion complexes in the gas phase opens the door to the synthesis of new salts with potential applications as organic cathodes and electrolytes in Li ion-batteries and beyond. Equally important, electron counting rules can be used effectively to guide the synthesis of electronegative species beyond super-and hyperhalogens, and hence opening the door for new oxidizing agents.Over the past 30 years the study of multiply charged molecular ions has been a topic of great interest 1 not only because they enable a fundamental understanding of interstellar chemistry but also for their potential as building blocks of salts and Zintl phase compounds, fusion devices, high intensity ion sources, and use in analytic mass spectrometry of large biomolecules. Multiply charged species are commonly seen in solutions or in a condensed phase where they are stabilized either by counterions or interaction with the solvent molecules. Their stability in the gas phase, however, is governed by a delicate balance between the repulsive Coulomb forces and attractive interaction generated by chemical bonding and charge/induceddipole interactions. Small multiply charged molecular negative ions in the gas phase are seldom stable due to spontaneous emission of electron (the so-called auto-detachment) or fragmentation into mono-anions. In the early 1990's observation of long-lived cluster di-anions such as C 60 2À could be explained 2 by the existence of substantial Coulomb barriers that hinder the emission of one of the excess electrons. More recently, electronic stability of di-anionic metal hexauoride complexes such as ZrF 6 2À , rst predicted by theory, 3-5 has been conrmed by photoelectron spectroscopy experiments, 6 but their thermodynamic stability is not addressed. How small a cluster can bind two extra electrons without auto-detaching or fragmenting remains an unanswered question. A classic example of a thermodynamically stable di-anion is B 12 H 12 2À. This cluster belongs to the class of closo-boranes, B n H n 2À , whose stability g...

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“…[33][34] This is reflected in the NBO charge on the Mg atom in MgB 12 H 12 . Figure 2 c shows that the charge on Mg is + 1.65 which is significantly larger than that in MgB 6 H 6 .…”

Section: Mgb 12 H 12mentioning

confidence: 99%

Functionalized Boranes for Hydrogen Storage

Pathak¹,

Pradhan²,

Hussain³

et al. 2011

ChemPhysChem

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Using density functional theory, the generalized gradient approximation for the exchange-correlation potential and Møller-Plesset perturbation theory we study the hydrogen uptake of Li- and Mg-doped boranes. Specifically, we calculate the structures and binding energies of hydrogen molecules sequentially attached to LiB(6)H(7), LiB(12)H(13), Li(2)B(6)H(6), Li(2)B(12)H(12), MgB(6)H(6), and MgB(12)H(12). Up to three H(2) molecules can be bound quasi-molecularly to each of the metal cations with binding energies per H(2) molecule ranging between 0.07 eV and 0.27 eV. The corresponding gravimetric densities lie in the range of 3.49 to 12 wt %, not counting the H atoms bound chemically to the B atoms.

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Reaction Intermediates during the Dehydrogenation of Metal Borohydrides: A Cluster Perspective

Cited by 33 publications

References 28 publications

Recent Progress in Metal Borohydrides for Hydrogen Storage

Recent Progress in Metal Borohydrides for Hydrogen Storage

Unusual stability of multiply charged organo-metallic complexes

Functionalized Boranes for Hydrogen Storage

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