Reversible hydrogen decomposition of KAlH4

Morioka, Hiroyuki; Kakizaki, Kenichi; Chung, Sai‐Cheong; Yamada, Atsuo

doi:10.1016/s0925-8388(02)01307-5

Cited by 147 publications

(135 citation statements)

References 21 publications

Supporting

Mentioning

120

Contrasting

Order By: Relevance

“…The reaction is very similar to that for NaAlH 4 given in Eq. 1, except that the two steps occur at higher temperatures near 573 K and 613 K, respectively [33,34]. The high temperature part of the phase diagram of KAlH 4 should thus be somewhat similar to those of the MAlH 4 materials discussed above, with a transformation into K 3 AlH 6 at high temperature also under pressure.…”

mentioning

confidence: 63%

“…For the heavier alkali metal alanates, KAlH 4 , RbAlH 4 and CsAlH 4 , and their M 3 AlH 6 counterparts, little is known about the high-pressure phase diagrams. There has been some recent interest in KAlH 4 since this material was reported to reversibly store and release hydrogen without the help of catalysts [33], but the low weight fraction of hydrogen makes it less attractive as a storage material. The reaction is very similar to that for NaAlH 4 given in Eq.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Pressure-Temperature Phase Relations in Complex Hydrides

Sundqvist

2009

SSP

View full text Add to dashboard Cite

Abstract. Interest in hydrogen as a future energy carrier in mobile applications has led to a strong increase in research on the structural properties of complex alkali metal and alkaline earth hydrides, with the aim to find structural phases with higher hydrogen densities. This contribution reviews recent work on the structural properties and phase diagrams of these complex hydrides under elevated pressures, an area where rapid progress has been made over the last few years. The materials discussed in greatest detail are LiAlH 4 , NaAlH 4 , Li 3 AlH 6 , Na 3 AlH 6 , LiBH 4 , NaBH 4 , and KBH 4 . All of these have been studied under high pressure by various methods such as X-ray or neutron scattering, Raman spectroscopy, differential thermal analysis or thermal conductivity measurements in order to find information on their structural phase diagrams. Based mainly on experimental studies, preliminary or partial phase diagrams are also given for six of these materials. In addition to this information, data are provided also on experimental results for a number of other complex hydrides, and theoretical predictions of new phases and structures under high pressures are reviewed for several materials not yet studied experimentally under high pressure.

show abstract

mentioning

confidence: 63%

mentioning

confidence: 99%

Pressure-Temperature Phase Relations in Complex Hydrides

Sundqvist

2009

SSP

View full text Add to dashboard Cite

show abstract

“…Since Bogdanović and Schwickardi have reported that the catalyzed sodium alanate ͑NaAlH 4 ͒ shows reversible hydrogen desorption and absorption reactions at moderate condition, 1 many researches have been done for alkali complex hydrides mainly from the viewpoint of kinetics. [2][3][4][5][6][7][8][9][10] Among alkali complex hydrides, lithium borohydride ͑LiBH 4 ͒ is one of the candidates for hydrogen storage materials because of its extremely high gravimetric hydrogen density ͑18 mass % ͒. LiBH 4 mixed with SiO 2 has been reported to desorb hydrogen below 673 K that is lower than pure LiBH 4 does.…”

Section: Introductionmentioning

confidence: 99%

Correlation between thermodynamical stabilities of metal borohydrides and cation electronegativites: First-principles calculations and experiments

et al. 2006

View full text Add to dashboard Cite

The thermodynamical stabilities for the series of metal borohydrides M͑BH 4 ͒ n ͑M = Li, Na, K, Cu, Mg, Zn, Sc, Zr, and Hf; n =1-4͒ have been systematically investigated by first-principles calculations. The results indicated that an ionic bonding between M n+ cations and ͓BH 4 ͔ − anions exists in M͑BH 4 ͒ n , and the charge transfer from M n+ cations to ͓BH 4 ͔ − anions is a key feature for the stability of M͑BH 4 ͒ n . A good correlation between the heat of formation ⌬H boro of M͑BH 4 ͒ n and the Pauling electronegativity of the cation P can be found, which is represented by the linear relation, ⌬H boro = 248.7 P − 390.8 in the unit of kJ/mol BH 4 . In order to confirm the predicted correlation experimentally, the hydrogen desorption reactions were studied for M͑BH 4 ͒ n ͑M = Li, Na, K, Mg, Zn, Sc, Zr, and Hf͒, where the samples of the later five borohydrides were mechanochemically synthesized. The thermal desorption analyses indicate that LiBH 4 , NaBH 4 , and KBH 4 desorb hydrogen to hydride phases. Mg͑BH 4 ͒ 2 , Sc͑BH 4 ͒ 3 , and Zr͑BH 4 ͒ 4 show multistep desorption reactions through the intermediate phases of hydrides and/or borides. On the other hand, Zn͑BH 4 ͒ 2 desorbs hydrogen and borane to elemental Zn due to instabilities of Zn hydride and boride. A correlation between the desorption temperature T d and the Pauling electronegativity P is observed experimentally and so P is an indicator to approximately estimate the stability of M͑BH 4 ͒ n . The enthalpy change for the desorption reaction, ⌬H des , is estimated using the predicted ⌬H boro and the reported data for decomposed product, ⌬H hyd/boride . The estimated ⌬H des show a good correlation with the observed T d , indicating that the predicted stability of borohydride is experimentally supported. These results are useful for exploring M͑BH 4 ͒ n with appropriate stability as hydrogen storage materials.

show abstract

“…Another promising class of materials for hydrogen storage are the Al-based complex hydrides, since Bogdanovic and Schwickardi showed that the decomposition of sodium alanate, NaAlH 4 , can be made reversible by the addition of Ti and Fe compounds as catalysts [20]. This stimulated the investigation of many other complex systems [21][22][23][24]. Among them, magnesium alanate, Mg(AlH 4 ) 2 , with 9.3 wt% of hydrogen, is also a potential hydrogen storage material.…”

Section: Introductionmentioning

confidence: 99%

Structural and optical properties of MgxAl1-xHy gradient thin films: a combinatorial approach

et al. 2006

View full text Add to dashboard Cite

The structural, optical and dc electrical properties of Mg x Al 1−x (0.2 ≤ x ≤ 0.9) gradient thin films covered with Pd/Mg are investigated before and after exposure to hydrogen. We use Hydrogenography, a novel high-throughput optical technique to map simultaneously all the hydride forming compositions and the kinetics thereof in the gradient thin film. Metallic Mg in the Mg x Al 1−x layer undergoes a metal-to-semiconductor transition and MgH 2 is formed for all Mg fractions x investigated. The presence of an amorphous Mg-Al phase in the thin film phase diagram enhances strongly the kinetics of hydrogenation. In the Al-rich part of the film, a complex H-induced segregation of MgH 2 and Al occurs. This uncommon large-scale segregation is evidenced by metal and hydrogen profiling using Rutherford backscattering spectrometry and resonant nuclear analysis based on the reaction 1 H( 15 N,αγ) 12 C. Besides MgH 2 , an additional semiconducting phase is found by electrical conductivity measurements around an atomic [Al]/[Mg] ratio of 2 (x = 0.33). This suggests that the film is partially transformed into Mg(AlH 4 ) 2 at around this composition.

show abstract

Reversible hydrogen decomposition of KAlH4

Cited by 147 publications

References 21 publications

Pressure-Temperature Phase Relations in Complex Hydrides

Pressure-Temperature Phase Relations in Complex Hydrides

Correlation between thermodynamical stabilities of metal borohydrides and cation electronegativites: First-principles calculations and experiments

Structural and optical properties of MgxAl1-xHy gradient thin films: a combinatorial approach

Contact Info

Product

Resources

About