Dehydrogenation characteristics of LiAlH 4 improved by in-situ formed catalysts

Cai, Jiaxing; Zang, Lei; Zhao, Lipeng; Liu, Jian; Wang, Yijing

doi:10.1016/j.jechem.2016.06.004

Cited by 27 publications

(7 citation statements)

References 40 publications

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“…Theoretically, LiAlH 4 is also an important coordination hydride hydrogen storage material. When heated in an inert atmosphere, it will undergo a two-step dehydrogenation reaction based on Equations (3) and (4) respectively [21,26,27], without considering the decomposition of LiH. 3LiAlH 4 → Li 3 AlH 6 + 2Al + 3H 2 (~160 °C; 5.3 wt.% H 2 ) Li 3 AlH 6 → 3LiH + Al + 3/2H 2 (210 °C; 2.6 wt.% H 2 )…”

Section: Introductionmentioning

confidence: 99%

Hydrogen Desorption Properties of LiBH4/xLiAlH4 (x = 0.5, 1, 2) Composites

Zhu

et al. 2019

Molecules

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A detailed analysis of the dehydrogenation mechanism of LiBH4/xLiAlH4 (x = 0.5, 1, 2) composites was performed by thermogravimetry (TG), differential scanning calorimetry (DSC), mass spectral analysis (MS), powder X-ray diffraction (XRD) and scanning electronic microscopy (SEM), along with kinetic investigations using a Sievert-type apparatus. The results show that the dehydrogenation pathway of LiBH4/xLiAlH4 had a four-step character. The experimental dehydrogenation amount did not reach the theoretical expectations, because the products such as AlB2 and LiAl formed a passivation layer on the surface of Al and the dehydrogenation reactions associated with Al could not be sufficiently carried out. Kinetic investigations discovered a nonlinear relationship between the activation energy (Ea) of dehydrogenation reactions associated with Al and the ratio x, indicating that the Ea was determined both by the concentration of Al produced by the decomposition of LiAlH4 and the amount of free surface of it. Therefore, the amount of effective contact surface of Al is the rate-determining factor for the overall dehydrogenation of the LiBH4/xLiAlH4 composites.

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Section: Introductionmentioning

confidence: 99%

Hydrogen Desorption Properties of LiBH4/xLiAlH4 (x = 0.5, 1, 2) Composites

Zhu

et al. 2019

Molecules

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“…This desorption rate was 30 times faster than that of the as-received LiAlH 4 . This enhancement may be correlated to the formation of surface defects and active materials through the reaction of the LiAlH 4 + 10 wt.% K 2 NbF 7 composite (Cai et al, 2016).…”

Section: Resultsmentioning

confidence: 97%

Influence of K2NbF7 Catalyst on the Desorption Behavior of LiAlH4

et al. 2020

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In this study, the modification of the desorption behavior of LiAlH 4 by the addition of K 2 NbF 7 was explored for the first time. The addition of K 2 NbF 7 causes a notable improvement in the desorption behavior of LiAlH 4 . Upon the addition of 10 wt.% of K 2 NbF 7 , the desorption temperature of LiAlH 4 was significantly lowered. The desorption temperature of the LiAlH 4 + 10 wt.% K 2 NbF 7 sample was lowered to 90 • C (first-stage reaction) and 149 • C (second-stage reaction). Enhancement of the desorption kinetics performance with the LiAlH 4 + 10 wt.% K 2 NbF 7 sample was substantiated, with the composite sample being able to desorb hydrogen 30 times faster than did pure LiAlH 4 . Furthermore, with the presence of 10 wt.% K 2 NbF 7, the calculated activation energy values for the first two desorption stages were significantly reduced to 80 and 86 kJ/mol; 24 and 26 kJ/mol lower than the as-milled LiAlH 4 . After analysis of the X-ray diffraction result, it is believed that the in situ formation of NbF 4 , LiF, and K or K-containing phases that appeared during the heating process promoted the amelioration of the desorption behavior of LiAlH 4 with the addition of K 2 NbF 7 .

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“…Thus, CeAl 2 and CeAl 4 alloys were directly mixed to NaAlH 4 and were found to be quite effective in reducing the activation energy of both steps, which were found in the range of 72-90 and 93-104 kJ/mol H 2 for first and second step decomposition [206,207]. Similar to NaAlH 4 system, several catalysts were developed for solving the kinetic problem of LiAlH 4 decomposition, which included Ti based halides [208][209][210][211], other metal halides [212][213][214][215][216][217][218], nano-sized oxides [219][220][221], carbon [222][223][224], etc. Recently a new class of complex precursors for metal doping are being used, such as K 2 TiF 6 [225,226], MnFe 2 O 4 [227,228], NiFe 2 O 4 [229], NiCo 2 O 4 [230], LiTi 2 O 4 [231].…”

Section: Catalysts For Alanatesmentioning

confidence: 99%

Catalytic Tuning of Sorption Kinetics of Lightweight Hydrides: A Review of the Materials and Mechanism

2018

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Hydrogen storage materials have been a subject of intensive research during the last 4 decades. Several developments have been achieved in regard of finding suitable materials as per the US-DOE targets. While the lightweight metal hydrides and complex hydrides meet the targeted hydrogen capacity, these possess difficulties of hard thermodynamics and sluggish kinetics of hydrogen sorption. A number of methods have been explored to tune the thermodynamic and kinetic properties of these materials. The thermodynamic constraints could be resolved using an intermediate step of alloying or by making reactive composites with other hydrogen storage materials, whereas the sluggish kinetics could be improved using several approaches such as downsizing and the use of catalysts. The catalyst addition reduces the activation barrier and enhances the sorption rate of hydrogen absorption/desorption. In this review, the catalytic modifications of lightweight hydrogen storage materials are reported and the mechanism towards the improvement is discussed.

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Dehydrogenation characteristics of LiAlH 4 improved by in-situ formed catalysts

Cited by 27 publications

References 40 publications

Hydrogen Desorption Properties of LiBH4/xLiAlH4 (x = 0.5, 1, 2) Composites

Hydrogen Desorption Properties of LiBH4/xLiAlH4 (x = 0.5, 1, 2) Composites

Influence of K2NbF7 Catalyst on the Desorption Behavior of LiAlH4

Catalytic Tuning of Sorption Kinetics of Lightweight Hydrides: A Review of the Materials and Mechanism

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