Role of native defects and the effects of metal additives on the kinetics of magnesium borohydride
Magnesium borohydride (Mg(BH 4 ) 2 ) has been considered as a potential material for hydrogen storage. In this paper, density functional theory studies have been carried out on native point defects and electrically active impurities (Ni and Ti) in Mg(BH 4 ) 2 . A detailed analysis of the geometrical...
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Veröffentlicht in: | Physical chemistry chemical physics : PCCP 2019-06, Vol.21 (21), p.11226-11233 |
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Hauptverfasser: | , , , , , , |
Format: | Artikel |
Sprache: | eng |
Online-Zugang: | Volltext |
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Zusammenfassung: | Magnesium borohydride (Mg(BH
4
)
2
) has been considered as a potential material for hydrogen storage. In this paper, density functional theory studies have been carried out on native point defects and electrically active impurities (Ni and Ti) in Mg(BH
4
)
2
. A detailed analysis of the geometrical structures, energetics and migration of the defects reveals that hydrogen related defects are charged and their formation energies are Fermi-level dependent. We propose a specific mechanism for the decomposition of Mg(BH
4
)
2
: the self-diffusion of Mg
i
2+
is the rate-limiting process for decomposing Mg(BH
4
)
2
. Moreover, Ni and Ti impurities can tailor the hydrogen desorption kinetics of Mg(BH
4
)
2
by shifting the Fermi level, but the effects of impurities on shifting the Fermi levels are related to how the impurity is incorporated into Mg(BH
4
)
2
.
The formation and migration of Mg
i
2+
are the rate-limiting processes for decomposing Mg(BH
4
)
2
. |
---|---|
ISSN: | 1463-9076 1463-9084 |
DOI: | 10.1039/c9cp01467e |