Structure and decomposition of zinc borohydride ammonia adduct: towards a pure hydrogen release

Gu, Qinfen; Gao, Liang; Guo, Yanhui; Tan, Yingbin; Tang, Ziwei; Wallwork, Kia S.; Zhang, Feiwu; Yu, Xuebin

doi:10.1039/c2ee02485c

Cited by 88 publications

(99 citation statements)

References 56 publications

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“…[36][37][38][39] Interestingly,d estabilization is observed for most metal borohydrides with low electronegativity (c p <~1.6), whereas metal borohydrides with ah igh electronegativity (c p >~1.6) are stabilized by NH 3 (i.e.,they releaseg as at higher temperatures). [4,15] However, the generalm echanism for decomposition is not fully understood.…”

Section: Mechanism For the Decomposition Of Ammine Metal Borohydridesmentioning

confidence: 92%

Ammine Calcium and Strontium Borohydrides: Syntheses, Structures, and Properties

et al. 2015

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A new series of solvent- and halide-free ammine strontium metal borohydrides Sr(NH3 )n (BH4 )2 (n=1, 2, and 4) and further investigations of Ca(NH3 )n (BH4 )2 (n=1, 2, 4, and 6) are presented. Crystal structures have been determined by powder XRD and optimized by DFT calculations to evaluate the strength of the dihydrogen bonds. Sr(NH3 )(BH4 )2 (Pbcn) and Sr(NH3 )2 (BH4 )2 (Pnc2) are layered structures, whereas M(NH3 )4 (BH4 )2 (M=Ca and Sr; P21 /c) are molecular structures connected by dihydrogen bonds. Both series of compounds release NH3 gas upon thermal treatment if the partial pressure of ammonia is low. Therefore, the strength of the dihydrogen bonds, the structure of the compounds, and the NH3 /BH4 (-) ratio for M(NH3 )n (BH4 )m have little influence on the composition of the released gasses. The composition of the released gas depends mainly on the thermal stability of the ammine metal borohydride and the corresponding metal borohydride.

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Section: Mechanism For the Decomposition Of Ammine Metal Borohydridesmentioning

confidence: 92%

Ammine Calcium and Strontium Borohydrides: Syntheses, Structures, and Properties

et al. 2015

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“…Thus the latter are often more thermally stable than their respective metal borohydride [104,130]. The stabilization may be due to complex formation and a shielding effect of the metal cation, which would otherwise be reduced to the metallic state, e.g., Zn(BH 4 ) 2 ·4NH 3 and Zn(BH 4 ) 2 ·2NH 3 [135]. Previously, a low NH 3 /BH 4 − ratio (n/m~1) and strong dihydrogen bonds were assumed to provide H 2 rich (and NH 3 poor) gas release during thermolysis.…”

Section: Metal Borohydrides Modified By Neutral Moleculesmentioning

confidence: 99%

“…The most extensive series of crystalline ammine metal borohydride is formed by Y(BH 4 ) 3 ·nNH 3 (n = 1, 2, 4, 5, 6 and 7), which illustrates the great structural flexibility ranging from cation complexes (n = 6 and 7), molecular neutral complexes (n = 4 and 5), one-dimensional chain like (n = 2), and two-dimensional layered structure (n = 1) [132]. Ammine metal borohydrides have been considered promising hydrogen storage materials, e.g., Al(BH 4 ) 3 ·6NH 3 , Li 2 Al(BH 4 ) 5 ·6NH 3 , and Zn(BH 4 ) 2 ·2NH 3 release 9 to 12 wt % H 2 in the temperature range 115 to 170 • C with traces of NH 3 [133][134][135].…”

Section: Metal Borohydrides Modified By Neutral Moleculesmentioning

confidence: 99%

Complex Metal Hydrides for Hydrogen, Thermal and Electrochemical Energy Storage

et al. 2017

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Hydrogen has a very diverse chemistry and reacts with most other elements to form compounds, which have fascinating structures, compositions and properties. Complex metal hydrides are a rapidly expanding class of materials, approaching multi-functionality, in particular within the energy storage field. This review illustrates that complex metal hydrides may store hydrogen in the solid state, act as novel battery materials, both as electrolytes and electrode materials, or store solar heat in a more efficient manner as compared to traditional heat storage materials. Furthermore, it is highlighted how complex metal hydrides may act in an integrated setup with a fuel cell. This review focuses on the unique properties of light element complex metal hydrides mainly based on boron, nitrogen and aluminum, e.g., metal borohydrides and metal alanates. Our hope is that this review can provide new inspiration to solve the great challenge of our time: efficient conversion and large-scale storage of renewable energy.

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“…12 In recent years, various studies have found that these metal borohydrides typically demonstrate improved hydrogen storage properties when complexed with ammonia, forming a new class of materials called metal borohydride ammoniates (MBAs). [13][14][15][16][17][18] Generally, MBAs tend to release hydrogen gas at more practical temperatures and greater purity than their plain MB counterparts. 13 Furthermore, recent experiments have mixed various MBAs with MBs or ammonia borane (NH 3 BH 3 ) to tune the H 2 release temperature and purity.…”

Section: Introductionmentioning

confidence: 99%

Decomposition mechanisms in metal borohydrides and their ammoniates

Welchman

Thonhauser

2017

J. Mater. Chem. A

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Ammoniation in metal borohydrides (MBs) with the form M (BH 4 ) x has been shown to lower their decomposition temperatures with M of low electronegativity (χ p 1.6), but raise it for high-χ p MBs (χ p 1.6). Although this behavior is just as desired, an understanding of the mechanisms that cause it is still lacking. Using ab initio methods, we elucidate those mechanisms and find that ammoniation always causes thermodynamic destabilization, explaining the observed lower decomposition temperatures for low-χ p MBs. For high-χ p MBs, we find that ammoniation blocks B 2 H 6 formation-the preferred decomposition mechanism in these MBs-and thus kinetically stabilizes those phases. The shift in decomposition pathway that causes the distinct change from destabilization to stabilization around χ p = 1.6 thus coincides with the onset of B 2 H 6 formation in MBs. Furthermore, with our analysis we are also able to explain why these materials release either H 2 or NH 3 gas upon decomposition. We find that NH 3 is much more strongly coordinated with higher-χ p metals and direct H 2 formation/release becomes more favorable in these materials. Our findings are of importance for unraveling the hydrogen release mechanisms in an important new and promising class of hydrogen storage materials, allowing for a guided tuning of their chemistry to further improve their properties.

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Structure and decomposition of zinc borohydride ammonia adduct: towards a pure hydrogen release

Cited by 88 publications

References 56 publications

Ammine Calcium and Strontium Borohydrides: Syntheses, Structures, and Properties

Ammine Calcium and Strontium Borohydrides: Syntheses, Structures, and Properties

Complex Metal Hydrides for Hydrogen, Thermal and Electrochemical Energy Storage

Decomposition mechanisms in metal borohydrides and their ammoniates

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