Crystal structures, phase stability, and decomposition reactions in the quaternary Mg-B-N-H hydrogen storage system

Yongsheng Zhang; David Farrell; Jun Yang; Andrea Sudik; C. Wolverton

doi:10.1021/jp500318e

Crystal structures, phase stability, and decomposition reactions in the quaternary Mg-B-N-H hydrogen storage system

Yongsheng Zhang^*, David Farrell, Jun Yang, Andrea Sudik, C. Wolverton

^*Corresponding author for this work

Materials Science and Engineering

Research output: Contribution to journal › Article › peer-review

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Abstract

Using the combination of DFT-based computational approaches and experimental measurements, we have studied the crystal structure, phase stability, and decomposition products of mixed Mg(NH₂) ₂/Mg(BH₄)₂ materials. We find the following: (i) DFT crystal structure prediction calculations (0 K) show the existence of a mixed Mg(NH₂)₂/Mg(BH₄)₂ phase, which is thermodynamically stable relative to its separated phases [Mg(NH ₂)₂ and Mg(BH₄)₂]. (ii) The DFT calculated phonon density of states of Mg(NH₂)(BH₄) is in good agreement with the peak positions from experimental PAS IR measurements (at the room temperature) of a ball-milled Mg(NH₂)₂/ Mg(BH₄)₂ mixture, suggesting the mixture is not merely a physical mixture of the individual compounds. (iii) The experimentally measured dehydrogenation temperature of the mixed Mg(NH₂)₂/ Mg(BH₄)₂ phase is lower than that of Mg(NH ₂)₂ or Mg(BH₄)₂, which further confirms that it is not a simply physical mixture of Mg(NH₂) ₂ and Mg(BH₄)₂. The observed amount of H ₂ release is 3.4 wt % at 250° and 8.3 wt % above 280°. (iv) From a combination of DFT, the grand-canonical linear programming (GCLP) method calculations, and PAS IR measurements of dehydrogenated samples, we identify the existence of the B-H bonds and linear N-B-N units in the decomposition of Mg(NH₂)₂/Mg(BH₄)₂. (v) Experimental desorption measurements reveal that the Mg(NH₂)₂/ Mg(BH₄)₂ mixed phase is irreversible, consistent with DFT calculated enthalpies in the range of -18 to +16 kJ/(mol H₂), too low for near-ambient reversible storage.

Original language	English (US)
Pages (from-to)	11193-11202
Number of pages	10
Journal	Journal of Physical Chemistry C
Volume	118
Issue number	21
DOIs	https://doi.org/10.1021/jp500318e
State	Published - May 29 2014

ASJC Scopus subject areas

Electronic, Optical and Magnetic Materials
Energy(all)
Physical and Theoretical Chemistry
Surfaces, Coatings and Films

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@article{481406a951df480ba3b44f6f78ab1822,

title = "Crystal structures, phase stability, and decomposition reactions in the quaternary Mg-B-N-H hydrogen storage system",

abstract = "Using the combination of DFT-based computational approaches and experimental measurements, we have studied the crystal structure, phase stability, and decomposition products of mixed Mg(NH2) 2/Mg(BH4)2 materials. We find the following: (i) DFT crystal structure prediction calculations (0 K) show the existence of a mixed Mg(NH2)2/Mg(BH4)2 phase, which is thermodynamically stable relative to its separated phases [Mg(NH 2)2 and Mg(BH4)2]. (ii) The DFT calculated phonon density of states of Mg(NH2)(BH4) is in good agreement with the peak positions from experimental PAS IR measurements (at the room temperature) of a ball-milled Mg(NH2)2/ Mg(BH4)2 mixture, suggesting the mixture is not merely a physical mixture of the individual compounds. (iii) The experimentally measured dehydrogenation temperature of the mixed Mg(NH2)2/ Mg(BH4)2 phase is lower than that of Mg(NH 2)2 or Mg(BH4)2, which further confirms that it is not a simply physical mixture of Mg(NH2) 2 and Mg(BH4)2. The observed amount of H 2 release is 3.4 wt % at 250° and 8.3 wt % above 280°. (iv) From a combination of DFT, the grand-canonical linear programming (GCLP) method calculations, and PAS IR measurements of dehydrogenated samples, we identify the existence of the B-H bonds and linear N-B-N units in the decomposition of Mg(NH2)2/Mg(BH4)2. (v) Experimental desorption measurements reveal that the Mg(NH2)2/ Mg(BH4)2 mixed phase is irreversible, consistent with DFT calculated enthalpies in the range of -18 to +16 kJ/(mol H2), too low for near-ambient reversible storage.",

author = "Yongsheng Zhang and David Farrell and Jun Yang and Andrea Sudik and C. Wolverton",

year = "2014",

month = may,

day = "29",

doi = "10.1021/jp500318e",

language = "English (US)",

volume = "118",

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journal = "Journal of Physical Chemistry C",

issn = "1932-7447",

publisher = "American Chemical Society",

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TY - JOUR

T1 - Crystal structures, phase stability, and decomposition reactions in the quaternary Mg-B-N-H hydrogen storage system

AU - Zhang, Yongsheng

AU - Farrell, David

AU - Yang, Jun

AU - Sudik, Andrea

AU - Wolverton, C.

PY - 2014/5/29

Y1 - 2014/5/29

N2 - Using the combination of DFT-based computational approaches and experimental measurements, we have studied the crystal structure, phase stability, and decomposition products of mixed Mg(NH2) 2/Mg(BH4)2 materials. We find the following: (i) DFT crystal structure prediction calculations (0 K) show the existence of a mixed Mg(NH2)2/Mg(BH4)2 phase, which is thermodynamically stable relative to its separated phases [Mg(NH 2)2 and Mg(BH4)2]. (ii) The DFT calculated phonon density of states of Mg(NH2)(BH4) is in good agreement with the peak positions from experimental PAS IR measurements (at the room temperature) of a ball-milled Mg(NH2)2/ Mg(BH4)2 mixture, suggesting the mixture is not merely a physical mixture of the individual compounds. (iii) The experimentally measured dehydrogenation temperature of the mixed Mg(NH2)2/ Mg(BH4)2 phase is lower than that of Mg(NH 2)2 or Mg(BH4)2, which further confirms that it is not a simply physical mixture of Mg(NH2) 2 and Mg(BH4)2. The observed amount of H 2 release is 3.4 wt % at 250° and 8.3 wt % above 280°. (iv) From a combination of DFT, the grand-canonical linear programming (GCLP) method calculations, and PAS IR measurements of dehydrogenated samples, we identify the existence of the B-H bonds and linear N-B-N units in the decomposition of Mg(NH2)2/Mg(BH4)2. (v) Experimental desorption measurements reveal that the Mg(NH2)2/ Mg(BH4)2 mixed phase is irreversible, consistent with DFT calculated enthalpies in the range of -18 to +16 kJ/(mol H2), too low for near-ambient reversible storage.

AB - Using the combination of DFT-based computational approaches and experimental measurements, we have studied the crystal structure, phase stability, and decomposition products of mixed Mg(NH2) 2/Mg(BH4)2 materials. We find the following: (i) DFT crystal structure prediction calculations (0 K) show the existence of a mixed Mg(NH2)2/Mg(BH4)2 phase, which is thermodynamically stable relative to its separated phases [Mg(NH 2)2 and Mg(BH4)2]. (ii) The DFT calculated phonon density of states of Mg(NH2)(BH4) is in good agreement with the peak positions from experimental PAS IR measurements (at the room temperature) of a ball-milled Mg(NH2)2/ Mg(BH4)2 mixture, suggesting the mixture is not merely a physical mixture of the individual compounds. (iii) The experimentally measured dehydrogenation temperature of the mixed Mg(NH2)2/ Mg(BH4)2 phase is lower than that of Mg(NH 2)2 or Mg(BH4)2, which further confirms that it is not a simply physical mixture of Mg(NH2) 2 and Mg(BH4)2. The observed amount of H 2 release is 3.4 wt % at 250° and 8.3 wt % above 280°. (iv) From a combination of DFT, the grand-canonical linear programming (GCLP) method calculations, and PAS IR measurements of dehydrogenated samples, we identify the existence of the B-H bonds and linear N-B-N units in the decomposition of Mg(NH2)2/Mg(BH4)2. (v) Experimental desorption measurements reveal that the Mg(NH2)2/ Mg(BH4)2 mixed phase is irreversible, consistent with DFT calculated enthalpies in the range of -18 to +16 kJ/(mol H2), too low for near-ambient reversible storage.

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JF - Journal of Physical Chemistry C

IS - 21

ER -

Crystal structures, phase stability, and decomposition reactions in the quaternary Mg-B-N-H hydrogen storage system

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