Reactivity of magnesium borohydride – Metal hydride composites, γ-Mg(BH4)2-MHx, M = Li, Na, Mg, Ca

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Reactivity of magnesium borohydride – Metal hydride composites, γ-Mg(BH4)2-MHx, M = Li, Na, Mg, Ca. / Grube, Elisabeth; Jensen, Steffen R.H.; Nielsen, Ulla Gro; Jensen, Torben R.

In: Journal of Alloys and Compounds, Vol. 770, 05.01.2019, p. 1155-1163.

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaperJournal articleResearchpeer-review

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Grube, Elisabeth ; Jensen, Steffen R.H. ; Nielsen, Ulla Gro ; Jensen, Torben R. / Reactivity of magnesium borohydride – Metal hydride composites, γ-Mg(BH4)2-MHx, M = Li, Na, Mg, Ca. In: Journal of Alloys and Compounds. 2019 ; Vol. 770. pp. 1155-1163.

Bibtex

@article{b057940795b844f5b3da73fd9a0475ac,
title = "Reactivity of magnesium borohydride – Metal hydride composites, γ-Mg(BH4)2-MHx, M = Li, Na, Mg, Ca",
abstract = "The reactivity and thermal decomposition of γ-Mg(BH4)2-MHx, M = Li, Na, Mg, and Ca composites has been examined with the objective of studying the hydrogen storage capability of the composites. The samples were prepared by manual grinding γ-Mg(BH4)2 with a metal hydride to obtain homogenous mixtures. In-situ synchrotron radiation powder X-ray diffraction (SR-PXD) and simultaneous thermogravimetric analysis, differential scanning calorimetry, and mass spectrometry was performed to analyse the decomposition mechanism, whereas solid-state 11B nuclear magnetic resonance spectroscopy and SR-PXD was used to investigate the decomposition products. Interestingly, substitution reactions take place between magnesium borohydride and lithium, sodium and calcium hydride forming the more stable metal borohydrides, M(BH4)x, M = Li, Na or Ca. The composite γ-Mg(BH4)2-LiH has a hydrogen release at T ∼380–420 °C, which indicates the formation of amorphous LiBH4 during decomposition. For the composites γ-Mg(BH4)2-NaH, formation of crystalline NaBH4 is observed by SR-PXD from T = 150–450 °C, and hydrogen release ascribed to NaBH4 is observed in MS data at T = 460–480 °C. γ-Mg(BH4)2-MgH2 composite decomposes as the individual constituents. β-Ca(BH4)2 is formed at T = 175–375 °C in the composites of γ-Mg(BH4)2-CaH2. Bragg diffraction from CaB6 at T > 370 °C is detected by SR-PXD for γ-Mg(BH4)2-CaH2 (1:0.5) but not for samples richer in CaH2. Release of diborane was not observed for any of the magnesium borohydride metal hydride composites.",
keywords = "Hydrogen storage, In-situ powder X-ray diffraction, Magnesium borohydride, Reactive hydride composites, Thermal decomposition",
author = "Elisabeth Grube and Jensen, {Steffen R.H.} and Nielsen, {Ulla Gro} and Jensen, {Torben R.}",
year = "2019",
month = "1",
day = "5",
doi = "10.1016/j.jallcom.2018.08.177",
language = "English",
volume = "770",
pages = "1155--1163",
journal = "Journal of Alloys and Compounds",
issn = "0925-8388",
publisher = "Elsevier BV",

}

RIS

TY - JOUR

T1 - Reactivity of magnesium borohydride – Metal hydride composites, γ-Mg(BH4)2-MHx, M = Li, Na, Mg, Ca

AU - Grube, Elisabeth

AU - Jensen, Steffen R.H.

AU - Nielsen, Ulla Gro

AU - Jensen, Torben R.

PY - 2019/1/5

Y1 - 2019/1/5

N2 - The reactivity and thermal decomposition of γ-Mg(BH4)2-MHx, M = Li, Na, Mg, and Ca composites has been examined with the objective of studying the hydrogen storage capability of the composites. The samples were prepared by manual grinding γ-Mg(BH4)2 with a metal hydride to obtain homogenous mixtures. In-situ synchrotron radiation powder X-ray diffraction (SR-PXD) and simultaneous thermogravimetric analysis, differential scanning calorimetry, and mass spectrometry was performed to analyse the decomposition mechanism, whereas solid-state 11B nuclear magnetic resonance spectroscopy and SR-PXD was used to investigate the decomposition products. Interestingly, substitution reactions take place between magnesium borohydride and lithium, sodium and calcium hydride forming the more stable metal borohydrides, M(BH4)x, M = Li, Na or Ca. The composite γ-Mg(BH4)2-LiH has a hydrogen release at T ∼380–420 °C, which indicates the formation of amorphous LiBH4 during decomposition. For the composites γ-Mg(BH4)2-NaH, formation of crystalline NaBH4 is observed by SR-PXD from T = 150–450 °C, and hydrogen release ascribed to NaBH4 is observed in MS data at T = 460–480 °C. γ-Mg(BH4)2-MgH2 composite decomposes as the individual constituents. β-Ca(BH4)2 is formed at T = 175–375 °C in the composites of γ-Mg(BH4)2-CaH2. Bragg diffraction from CaB6 at T > 370 °C is detected by SR-PXD for γ-Mg(BH4)2-CaH2 (1:0.5) but not for samples richer in CaH2. Release of diborane was not observed for any of the magnesium borohydride metal hydride composites.

AB - The reactivity and thermal decomposition of γ-Mg(BH4)2-MHx, M = Li, Na, Mg, and Ca composites has been examined with the objective of studying the hydrogen storage capability of the composites. The samples were prepared by manual grinding γ-Mg(BH4)2 with a metal hydride to obtain homogenous mixtures. In-situ synchrotron radiation powder X-ray diffraction (SR-PXD) and simultaneous thermogravimetric analysis, differential scanning calorimetry, and mass spectrometry was performed to analyse the decomposition mechanism, whereas solid-state 11B nuclear magnetic resonance spectroscopy and SR-PXD was used to investigate the decomposition products. Interestingly, substitution reactions take place between magnesium borohydride and lithium, sodium and calcium hydride forming the more stable metal borohydrides, M(BH4)x, M = Li, Na or Ca. The composite γ-Mg(BH4)2-LiH has a hydrogen release at T ∼380–420 °C, which indicates the formation of amorphous LiBH4 during decomposition. For the composites γ-Mg(BH4)2-NaH, formation of crystalline NaBH4 is observed by SR-PXD from T = 150–450 °C, and hydrogen release ascribed to NaBH4 is observed in MS data at T = 460–480 °C. γ-Mg(BH4)2-MgH2 composite decomposes as the individual constituents. β-Ca(BH4)2 is formed at T = 175–375 °C in the composites of γ-Mg(BH4)2-CaH2. Bragg diffraction from CaB6 at T > 370 °C is detected by SR-PXD for γ-Mg(BH4)2-CaH2 (1:0.5) but not for samples richer in CaH2. Release of diborane was not observed for any of the magnesium borohydride metal hydride composites.

KW - Hydrogen storage

KW - In-situ powder X-ray diffraction

KW - Magnesium borohydride

KW - Reactive hydride composites

KW - Thermal decomposition

UR - http://www.scopus.com/inward/record.url?scp=85052482248&partnerID=8YFLogxK

U2 - 10.1016/j.jallcom.2018.08.177

DO - 10.1016/j.jallcom.2018.08.177

M3 - Journal article

VL - 770

SP - 1155

EP - 1163

JO - Journal of Alloys and Compounds

JF - Journal of Alloys and Compounds

SN - 0925-8388

ER -