Pressure and temperature dependence of the decomposition pathway of LiBH4

Yan, Yigang; Remhof, Arndt; Hwang, Son Jong; Li, Haiwen; Mauron, Philippe; Orimo, Shin Ichi; Züttel, Andreas

doi:10.1039/c2cp40131b

Cited by 80 publications

(91 citation statements)

References 40 publications

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“…Moreover, the experimental results obtained by Mauron et al [44] show a limited agreement with calculations, approaching the stable decomposition reaction (15) at the highest pressure (about 10 6 Pa) and temperature, but tend to metastable reaction (17) at ambient pressure and lower temperatures. In fact, in a recently published paper from the same group [57], it is suggested that decomposition according to reaction (17) seems kinetically favoured, whereas reaction (15) is kinetically hindered. In fact, in order to promote reaction (15) and overcome the kinetic barrier, the temperature has to be signifi-cantly increased.…”

Section: Consistency Of Results and Discussionmentioning

confidence: 99%

A thermodynamic assessment of LiBH4

Kharbachi

Pinatel

Nuta

et al. 2012

Calphad

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a b s t r a c t Thermodynamic data of the LiBH 4 compound are reviewed and critically assessed. On the basis of literature data of heat capacity, heat of formation, temperature and enthalpy of phase transitions, a CALPHAD optimized Gibbs energy function is derived for the condensed phases i.e. orthorhombic and hexagonal solid phases and the liquid phase. Considering hydrogen as an ideal gas phase, the thermodynamics of decomposition reactions of LiBH 4 is calculated, showing good agreement with existing experimental data.

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Section: Consistency Of Results and Discussionmentioning

confidence: 99%

A thermodynamic assessment of LiBH4

Kharbachi

Pinatel

Nuta

et al. 2012

Calphad

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“…Metal dodecaborates M 2/n B 12 H 12 (n is the valence of M) have been widely regarded as a dehydrogenation intermediate of metal borohydrides M(BH 4 ) n with a high gravimetric hydrogen density of 10 mass% [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. The formation of M 2/n B 12 H 12 , despite is still controversial, largely depends on the dehydrogenation temperature, hydrogen backpressure, particle size and sample pretreatment [11][12][13][14][15][16][17][18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

“…The formation of M 2/n B 12 H 12 , despite is still controversial, largely depends on the dehydrogenation temperature, hydrogen backpressure, particle size and sample pretreatment [11][12][13][14][15][16][17][18][19][20][21]. Due to the strong B-B bonds in an icosahedral boron cage B 12 , the intermediate comprising of polyatomic anion [B 12 H 12 ] 2´h as been widely regarded at the main obstacle for the rehydrogenation of M(BH 4 ) n [5,[22][23][24].…”

Section: Introductionmentioning

confidence: 99%

Thermal Decomposition of Anhydrous Alkali Metal Dodecaborates M2B12H12 (M = Li, Na, K)

Akiba

2015

Energies

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Metal dodecaborates M 2/n B 12 H 12 are regarded as the dehydrogenation intermediates of metal borohydrides M(BH 4 ) n that are expected to be high density hydrogen storage materials. In this work, thermal decomposition processes of anhydrous alkali metal dodecaborates M 2 B 12 H 12 (M = Li, Na, K) synthesized by sintering of MBH 4 (M = Li, Na, K) and B 10 H 14 have been systematically investigated in order to understand its role in the dehydrogenation of M(BH 4 ) n . Thermal decomposition of M 2 B 12 H 12 indicates multistep pathways accompanying the formation of H-deficient monomers M 2 B 12 H 12´x containing the icosahedral B 12 skeletons and is followed by the formation of (M 2 B 12 H z ) n polymers. The decomposition behaviors are different with the in situ formed M 2 B 12 H 12 during the dehydrogenation of metal borohydrides.

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“…54,55 Decomposition of NaBH 4 at p(H 2 ) B 0 in the TGA experiment resulted in loss of the sample possibly by 'foaming', whereas a slow loss of 6 wt% H 2 over 105 h was observed at p(H 2 ) B 1 bar using the Sieverts method. Furthermore, the results presented here suggest that utilization of sodium fluoride as an additive may eliminate foaming of the sample.…”

mentioning

confidence: 99%

Hydrogen–fluorine exchange in NaBH4–NaBF4

Rude

Filsø

D’Anna

et al. 2013

Phys. Chem. Chem. Phys.

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a Hydrogen-fluorine exchange in the NaBH 4 -NaBF 4 system is investigated using a range of experimental methods combined with DFT calculations and a possible mechanism for the reactions is proposed. Fluorine substitution is observed using in situ synchrotron radiation powder X-ray diffraction (SR-PXD) as a new Rock salt type compound with idealized composition NaBF 2 H 2 in the temperature range T = 200 to 215 1C. Combined use of solid-state 19 F MAS NMR, FT-IR and DFT calculations supports the formation of a BF 2 H 2 complex ion, reproducing the observation of a 19 F chemical shift at 144.2 ppm, which is different from that of NaBF 4 at 159.2 ppm, along with the new absorption bands observed in the IR spectra. After further heating, the fluorine substituted compound becomes X-ray amorphous and decomposes to NaF at B310 1C. This work shows that fluorine-substituted borohydrides tend to decompose to more stable compounds, e.g. NaF and BF 3 or amorphous products such as closo-boranes, e.g. Na 2 B 12 H 12 . The NaBH 4 -NaBF 4 composite decomposes at lower temperatures (300 1C) compared to NaBH 4 (476 1C), as observed by thermogravimetric analysis. NaBH 4 -NaBF 4 (1 : 0.5) preserves 30% of the hydrogen storage capacity after three hydrogen release and uptake cycles compared to 8% for NaBH 4 as measured using Sievert's method under identical conditions, but more than 50% using prolonged hydrogen absorption time. The reversible hydrogen storage capacity tends to decrease possibly due to the formation of NaF and Na 2 B 12 H 12 . On the other hand, the additive sodium fluoride appears to facilitate hydrogen uptake, prevent foaming, phase segregation and loss of material from the sample container for samples of NaBH 4 -NaF.

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Pressure and temperature dependence of the decomposition pathway of LiBH4

Cited by 80 publications

References 40 publications

A thermodynamic assessment of LiBH4

A thermodynamic assessment of LiBH4

Thermal Decomposition of Anhydrous Alkali Metal Dodecaborates M2B12H12 (M = Li, Na, K)

Hydrogen–fluorine exchange in NaBH4–NaBF4

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