Ternary amide-hydride system: A study on LiAl(NH2)4-LiAlH4 interaction

Article abstract of DOI:10.1016/j.jallcom.2019.03.234

LiAl(NH₂)₄ is a ternary amide that readily decomposes to release ammonia at temperatures as low as ～ 90 °C. Owing to such instability as compared to binary amides, we hypothesize that the dehydrogenation mechanism involving ternary amide-hydride interaction would be significantly different from those of binary metal amide-hydride interaction. Therefore, in this study, interaction of LiAl(NH₂)₄ and LiAlH₄ has been investigated by means of mechanical milling and thermal method. It was found that dehydrogenation occurred spontaneously during the milling process and the rate of dehydrogenation increased with increasing amount of LiAlH₄, suggesting an ion migration mediated dehydrogenation. As reaction progressed, the formation of Li₃AlH₆ as an intermediate was detected and a total of 8 equiv. of H₂ (7.5 wt%) can be released, forming LiH and AlN as the final product. In contrast, heating the homogenously ground LiAl(NH₂)₄ and LiAlH₄ sample resulted in the release of NH₃ at low temperatures, indicating that NH₃ mediation would take place in case of dehydrogenation. Further increase in temperature resulted in a rapid release of hydrogen from the interaction of the LiAl(NH)₂ and LiAlH₄. It was also found that hydride with higher basicity is required to trigger amide-hydride interaction for dehydrogenation at low temperatures.

Full text of DOI:10.1016/j.jallcom.2019.03.234

Accepted Manuscript
Ternary amide-hydride system: A study on LiAl(NH ) -LiAlH interaction
2 4
4
Yong Shen Chua, Zhitao Xiong, Guotao Wu, Ping Chen
PII:
S0925-8388(19)31060-6
DOI:
https://doi.org/10.1016/j.jallcom.2019.03.234
JALCOM 49998
Reference:
To appear in: Journal of Alloys and Compounds
Received Date: 30 January 2019
Revised Date: 14 March 2019
Accepted Date: 15 March 2019
Please cite this article as: Y.S. Chua, Z. Xiong, G. Wu, P. Chen, Ternary amide-hydride system: A study
on LiAl(NH ) -LiAlH interaction, Journal of Alloys and Compounds (2019), doi: https://doi.org/10.1016/
2 4
4
j.jallcom.2019.03.234.
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ACCEPTED MANUSCRIPT
Ternary Amide-Hydride System: A Study on LiAl(NH2)4-LiAlH4 Interaction
Yong Shen Chua,1* Zhitao Xiong,2* Guotao Wu2 and Ping Chen2
1School of Chemical Sciences, Universiti Sains Malaysia, 11800 USM, Pulau Pinang, Malaysia.
2Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road,
116023, Dalian, P. R. China.
Abstract
LiAl(NH2)4 is a ternary amide that readily decomposes to release ammonia at temperatures as low as ~ 90 °C.
Owing to such instability as compared to binary amides, we hypothesize that the dehydrogenation mechanism
involving ternary amide-hydride interaction would be significantly different from those of binary metal amide-
hydride interaction. Therefore, in this study, interaction of LiAl(NH2)4 and LiAlH4 has been investigated by
means of mechanical milling and thermal method. It was found that dehydrogenation occurred spontaneously
during the milling process and the rate of dehydrogenation increased with increasing amount of LiAlH4,
suggesting an ion migration mediated dehydrogenation. As reaction progressed, the formation of Li3AlH6 as an
intermediate was detected and a total of 8 equiv. of H2 (7.5 wt%) can be released, forming LiH and AlN as the
final product. In contrast, heating the homogenously ground LiAl(NH2)4 and LiAlH4 sample resulted in the
release of NH3 at low temperatures, indicating that NH3 mediation would take place in case of
dehydrogenation. Further increase in temperature resulted in a rapid release of hydrogen from the interaction
of the LiAl(NH)2 and LiAlH4. It was also found that hydride with higher basicity is required to trigger amide-
hydride interaction for dehydrogenation at low temperatures.
Keywords
Amide-hydride interaction; Dehydrogenation; Ion migration mechanism; NH3 mediation mechanism;

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Hydrogen storage
1.0
Introduction
Rapid development in fuel cell technologies arouses a breakthrough in the field of hydrogen storage.
Conventional storage methods, including compressed hydrogen, liquefied hydrogen and metal hydride, do not
meet the volumetric and gravimetric densities requirements as described in 2020 DOE target [1]. Research
efforts were presently moved to borohydrides [2, 3], metal organic frameworks [4], alanates [3] and metal-N-H
systems [5, 6]. In particular, the discovery of reversible hydrogen storage on LiNH2-LiH system in 2002
triggered intensive investigations on amide-hydride systems [7]. Metal hydrides, MH as reported, is known to
play an important role in destablizing metal amides, including binary [8-10] and ternary [11-14] amides, to
allow dehydrogenation to occur at much reduced temperatures with negligible emission of NH3. Over the past
10 years, it has been debated whether dehydrogenation process in amide-hydride system is governed by ion
migration mechanism or NH3 mediated mechanism. Chen et al. [15] suggested that the remarkable
improvement in the dehydrogenation properties of MNH2-MH system is due to the ion migration as results of
the high combination potential of the two oppositely charged Hδ+ Hδ- situating respectively in amide and
hydride. Ichikawa et al. [16] on the other hand suggested that the improvement is ascribed to the lowered
MNH2 decomposition temperature as results of the introduction of metal hydride, releasing NH3 that reacts
spontaneously with MH. However, recent research showed that both mechanisms are valid and the mechanism
involved is mainly governed by the ions mobility [17]. In Li2NH2Br [18], the LiNH2 moiety is constrained by
the cage of Br- anions. Due to the limited mobility of LiNH2 moiety, the hydrogen desorption from Li2NH2Br-
2LiH system appears to follow NH3 mediated mechanism. In contrast, Li+ (from LiH) and H+ (from LiNH2)
ions migration at the interface play important roles leading to hydrogen formation when LiNH2 and LiH are
intimately in contact.
Unlike LiNH2-LiH system, the interaction of LiAlH4 (or NaAlH4) and LiNH2 (or NaNH2) proceed
spontaneously. Eventhough the decomposition of NaNH2 and LiNH2 require high temperatures of ca. 210 °C
[20] and 350 °C [17], respectively, in the presence of LiAlH4, the reaction thermodynamic changes

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significantly, releasing most of the hydrogen during the mechanical milling process [8, 9, 19, 20]. This result
manifests that dehydrogenation via ion migration is more favorable than NH3 mediated mechanism. Different
from binary amides, LiAl(NH2)4 is a ternary amide which decomposes to release NH3 at much lower
temperatures (95 °C) as compared to LiNH2 and NaNH2, requiring lesser energy for its decomposition.
Therefore, when LiAl(NH2)2 is used as an amide source in amide-hydride reaction, the dehydrogenation
mechanism may be different from that of binary amide-hydride system. In 2007, Janot et al. [21] first
investigated the interaction of ternary amide-hydride system focusing on LiAl(NH2)4-LiH (1:4). In their study,
they found that the post milled LiAl(NH2)4-LiH began to dehydrogenate even at room temperature. Such
improvement was attributed to the catalytic role of LiH as results of the dihydrogen interaction between amide
and hydride. Despite the author suggested NH3 mediation as the dehydrogenation mechanism, there is no clear
evidence showing the preference of NH3 mediated mechanism over the ion migration mechanism in the
dehydrogenation process.
More recently, the interactions of ternary amides and borohydrides were investigated out by Hauback et al.
[12]. It was found that milling equimolar of LiAl(ND2)4 and LiBH4 resulted in the formation of new compound,
-
Li2Al(ND2)4BH4. This compound decomposed in a stepwise manner, releasing ND3 from the Al(ND2)4 unit
-
and H2 from BH4 unit in Li2Al(ND2)4BH4, separately. Neither the ND2+ nor ND3 interacts with the [BH4]- unit
to induce dehydrogenation at low temperatures. Similar results were observed in Li(NH3)nBH4, n = 1, 2, 3, 4
which desorbs NH3 reversibly rather than interact with [BH4]- to form H2 [22].
As LiAlH4 represents an important source of hydride in amide-hydride interactions and its interaction with
ternary amide remains unclear, therefore it is essential to study the interaction of LiAl(NH2)4-LiAlH4 under
different conditions and understand the dehydrogenation mechanism and pathway involved. The influence of
hydrides of different basicity towards the interaction with LiAl(NH2)4 are also discussed in this study.
2.0 Experimental
LiAlH4 (Fluka, 97%) was used as received. LiAl(NH2)4 was on-site synthesized by mechanical milling
LiAlH4 in purified ammonia gas atmosphere at room temperature. Detailed description of the synthesis can be

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found elsewhere [23]. Hydrogen was detected at the end of reaction and the weight gain of the solid suggested
the occurrence of following reaction (R1):
LiAlH4 + 4NH3 → LiAl(NH2)4 + 4H2
(1)
LiAl(NH2)4-LiAlH4 in molar ratios of 1:1, 1:2 and 1:3 were mechanically milled using a Retsch PM400
planetary mill. The rotation speed was regulated at 120 rpm and the ball-to-sample ratio was about 30. As
milling progressed, pressure increase inside the milling vessel was observed, signaling a spontaneous reaction
to form gaseous product has occurred. Time dependence of hydrogen pressure reading in the milling processes
were recorded by connecting the milling vessel to a pressure gauge. Therefore, the amount of desorbed
hydrogen can be calculated by applying ideal gas state of equation. One of the concerns on amide-hydride
system is the production of ammonia. To precisely detect the presence of ammonia gas, gas in milling vessel
was also connected to pink cobalt (II) nitrate solution to observe color change. In the event when small amount
of NH3 was presented in the gaseous product, green precipitate of Co(OH)2(H2O)4 shall be detected. In fact, in
all three post-milled samples, no color change was observed.
Structure identifications were conducted on a Bruker D8-advance X-Ray Diffractometer (XRD) using a
XRD cell with Pt base. N-H stretches in the reactant and post milled samples were monitored by a Perkin
7
Elmer FT-IR-3000 in DRIFT mode. Alterations of chemical environment of Li and 27Al nuclei in the milling
process were monitored by a DRX 400 magic angle spinning (MAS) solid state NMR. Lithium chloride and
aluminum nitrate solution were used as references.
The decomposition behavior of the samples were investigated by using a custom made temperature-
programmed-desorption coupled with a mass spectrometer and the corresponding heat effects were measured
on a DSC 204HP unit. A dynamic flow mode was employed with purified argon gas as carrier gas and the
heating was set at 2 °C/min. All sample handlings were carried out in an Argon filled MBRAUN glovebox to
prevent oxygen and moisture contaminations.
3.0 Result and Discussion

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3.1
Interaction of LiAl(NH2)4-LiAlH4 (1:1, 1:2, 1:3) via mechanical milling
One of the kinetic barriers in solid-solid interaction is mass transition and generally, intimate contact of
the reactants in solid mixture is demanded to overcome this barrier. Therefore, the samples were mechanically
milled to reduce their particle size to enhance the interactions between the starting materials. To avoid
additional heat from milling machine building up inside the milling vessel a low milling speed of 120 rpm was
chosen. In addition, solid interaction between LiAl(NH2)4 and LiAlH4 was not violent but somewhat
controllable at this milling speed, allowing operations such as pressure monitoring and intermediate collection
at different intervals of interaction. Figure 1 shows the pressure variations inside the milling vessel as a
function of time. 3.7 equiv. H2, 7.6 equiv. H2 and 8 equiv. of H2 (or 5.4 wt%, 8.7 wt% and 7.5 wt% of H2) can
be released upon extensively milling LiAl(NH2)4-LiAlH4 mixture in molar ratios of 1:1, 1:2 and 1:3,
respectively. Up to 70% of hydrogen (5.7 wt%) can be released from 1:3 sample within 2 hours of milling. For
comparison, LiAlH4 and LiAl(NH2)4 were individually milled under the same conditions. LiAlH4 was stable
against mechanical milling at 120 rpm as no pressure build up was detected, in agreement with the previous
reports [8]. As for LiAl(NH2)4, no gaseous product was found in the first 3 hours but detectable amount of
ammonia was evolved only after milling for 22 h. These results suggest that the rapid hydrogen desorption
from LiAl(NH2)4-LiAlH4 can only be resulted from the interaction of the two starting precursors. Furthermore,
the increasing rate of dehydrogenation (dH/dt) with increasing amount of LiAlH4 (Figure 1, inset) clearly
manifests ion migration mechanism in the dehydrogenation process. If NH3 mediation dehydrogenation were
to take place, the amount of LiAlH4 should have no big effect on the rate of dehydrogenation.

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LiAl(NH2)4-LiAlH4
(1:3)
8
6
4
2
0
(1:2)
6
3
0
(1:1)
0
1
2
0
10
20
Time (h)
30
40
Figure 1. Time dependence hydrogen desorption at ambient temperature and at a milling speed of 120 rpm.
The inset shows the dehydrogenations occur at the early stage of mechanical milling.
3.2
Dehydrogenation pathway of LiAl(NH2)4-LiAlH4 (1:3)
To understand the dehydrogenation pathway, LiAl(NH2)4-LiAlH4 in a molar ratio of 1:3 was further
investigated in detail by collecting the samples at different milling intervals and further characterized by FTIR,
XRD and NMR. As shown in FTIR spectra (Figure 2), self-made LiAl(NH2)4 presented five distinct -NH2
bands at 3406, 3397, 3357, 3337 and 3297 cm-1. As milling progressed, these five bands gradually disappeared,
suggesting the consumption of NH2 group in the milling process and the post milled samples are of –NH2 free
structure. XRD analyses (Figure 3) also revealed the diminishing diffraction patterns of LiAlH4 and
LiAl(NH2)4 with milling time and finally these patterns disappeared. Interestingly, diffraction pattern of
Li3AlH6 was detected when 5 equiv. H2 were evolved, suggesting its existence as an intermediate species in the
interaction of LiAl(NH2)4-LiAlH4. However, the amorphous nature of the post milled samples impedes the
structural analysis on the final product formed. In order to achieve a better crystallinity, the final product was
annealed at 400 °C and the resulting XRD pattern evidenced the presence of AlN and LiH in the sample.
Magic angle spinning solid state NMR (MAS NMR) was also employed to investigate the chemical

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7
environment of 27Al and Li. Figure 4(A) shows the 27Al NMR spectra of the post milled LiAl(NH2)4-LiAlH4
(1:3) collected at different milling intervals. It can be seen that the ground LiAl(NH2)4-LiAlH4 (1:3) mixture
displayed two overlapping peaks which are resulted from the superposition of the starting materials,
LiAl(NH2)4 and LiAlH4 at 91.9 and 120.7 ppm, respectively. Prolonging mechanical milling treatment the
resonances of the starting materials became weaker and finally disappeared. The LiAl(NH2)4-LiAlH4 (1:3)
sample evolving 4 and 5 equiv. H2 demonstrated a small peak centered at -36.1 ppm which can be assigned to
Al in six-coordinated [AlH6]3- sites of Li3AlH6, agreeing with the XRD results. When 5 equiv. H2 were evolved
from LiAl(NH2)4-LiAlH4 (1:3), no LiAl(NH2)4 resonance can be observed. Instead, a broad and asymmetry
resonance centered at 105.7 ppm was detected. Since the resonance falls between Al in LiAlH4 (93 ppm) and
Al in AlN (114 ppm), the formation of intermediate compounds with (AlH4-xNx) coordination sphere is thus
highly possible. A similar observation was also reported by Xiong et al. [24] in the interaction of LiAlH4-
2LiNH2. At the end of mechanical milling, the broad asymmetric resonance shifted downfield to 112.7 ppm,
closer to the chemical shift of four coordinated AlN4 environment in AlN (114 ppm). The asymmetry of the
peak may be due to the remaining of (AlH4-xNx) in the sample. Figure 4(B) shows that ground sample
7
7
possessed LiAl(NH2)4-like Li environment at 2.0 ppm, which also overlapped with the Li resonance in
LiAlH4. As the mechanical milling progressed, the peak centered at 2.0 ppm shifted upfield towards a LiH-like
environment. In conjunction with the FTIR, XRD and NMR analyses, the complete reaction pathway can be
realized by following equation (R2):
LiAl(NH2)4 + 3LiAlH4 → 4LiH + 4AlN + 8H2 (7.5 wt% H2)
(2)

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a
b
c
d
3600
3400
3200
3000
2800
2600
Wavenumber (cm-1)
Figure 2. FTIR spectra of self-made LiAl(NH2)4 (a), milled LiAl(NH2)4-LiAlH4 (1:3) with 4 equiv. H2 evolved
(b), 5 equiv. H2 evolved (c) and 8 equiv. H2 evolved (d).
o
∆
#
LiAlH4
LiH
AlN
Pt
• LiAl(NH2)4
♦
o
o
o
Li3AlH6
•
o
o
o
o
o
o
o
o
•
o
o
o
•
•
o
a
b
•
•
o
♦
♦
♦
♦
♦
♦
#
c
#
∆
∆
d
e
#
#
∆
10
20
30
2 theta (
40
50
°
)
Figure 3. XRD patterns of the ground LiAl(NH2)4-LiAlH4 (1:3) (a), milled LiAl(NH2)4-LiAlH4 (1:3) with 4
equiv. H2 evolved (b), 5 equiv. H2 evolved (c), 8 equiv. H2 evolved (d) and further annealed at 400
°C (e). Peaks correspond to platinum (Pt) base are marked with asterisks.

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27Al NMR
(B)
7Li NMR
(A)
d
*
d
c
c
b
b
*
a
a
f
*
h
g
h
e
e
150 100
50
0
-50
10
0
-10
Chemical shift (ppm)
Figure 4. 27Al (A) and 7Li (B) MAS solid state NMR spectra of LiAl(NH2)4-LiAlH4 (1:3) ground sample (a),
milled with 4 equiv. H2 evolved (b), 5 equiv. H2 evolved (c), 8 equiv. H2 evolved (d), self-made
LiAl(NH2)4 (e), LiH (f), AlN (g) and LiAlH4 (h). Asterisks denote the spinning sidebands.
3.3
Interaction of LiAl(NH2)4-LiAlH4 (1:3) via thermal method
In order to compare the influence of the sample preparation (mechanical milling vs thermal method)
towards the dehydrogenation mechanism, in a separate experiment, LiAl(NH2)4 and LiAlH4 mixture in the
molar ratio of 1:3 was ground gently using mortar and pester to minimize their interactions and the
decomposition was investigated by using TPD-MS and DSC. XRD characterization of the ground sample
(Figure 3) clearly demonstrated a diffraction pattern which resembles to the combined patterns of LiAlH4 and
LiAl(NH2)4, indicating a physical mixture of the two starting materials. Figure 5 shows the TPD-MS results of
the ground LiAl(NH2)4-LiAlH4 (1:3). As can be seen, only NH3 can be detected at ca. 100 °C which is
attributed to the decomposition of LiAl(NH2)4 (R3). DSC analysis shown in Figure 6 further confirms the
existence of only endothermic NH3 release at ~110 °C. Surprisingly, the release of NH3 did not trigger the
secondary reaction with LiAlH4 to release H2. This result is in contrary with the Luo’s work which suggested a
rapid interaction between NH3 and LiAlH4 to release H2 on demand [25]. This difference could be attributed to

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the fact that the experiments reported by Luo et al. were carried out by dosing NH3 into a LiAlH4 filled
container, while the current TPD-MS was carried out in an open flow mode whereby the NH3 released from
LiAl(NH2)4 diffused through LiAlH4 rapidly as the sample was directly exposed to the flowing inert gas. In
their experiments, NH3 has a longer contact time with LiAlH4 in the container, thus trapping all the NH3
completely and producing H2. In contrast, a relatively shorter contact time is expected under an open flow
mode, inhibiting the interaction between NH3 and LiAlH4.
Further increasing temperature resulted in the dehydrogenation which dehydrogenation pattern has
changed slightly as compared to that observed in the decomposition of pristine LiAlH4 [26]. A rapid release of
hydrogen at 158 °C can be clearly observed near the shoulder of the first dehydrogenation step of LiAlH4. It
corresponds to a strong exothermic process in DSC analysis which evidences an interaction between the
decomposed residue LiAl(NH)2 and LiAlH4 to release H2. Due to the fact that LiAl(NH)2 is metastable and it
exothermically transforms into LiNH2 and AlN (R4) [11], thus, it is plausible to attribute the rapid release of
H2 to the interaction of LiNH2 and LiAlH4. This assumption is further supported by the observation of a similar
phenomenon in the interaction of NaNH2 and LiAlH4 [9].
LiAl(NH2)4 → LiAl(NH)2 + 2NH3
LiAl(NH)2 → LiNH2 + AlN
(3)
(4)
The remaining of the process matches well with the characteristic decomposition of LiAlH4 which
involves endothermic phase transition at ~160 °C, exothermic dehydrogenation of LiAlH4 to Li3AlH6, LiH and
Al at 175 °C and endothermic dehydrogenation of Li3AlH6 to LiH and Al at 220 °C.

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LiAl(NH2)4-LiAlH4 (1:3)
H2
NH3
I
(NH3) x 100
LiAl(NH2)4
0
50
100
150
200
250
300
Temperature (oC)
Figure 5. TPD-MS curves of ground LiAl(NH2)4-LiAlH4(1:3) (top) and self-made LiAl(NH2)4 (bottom).
2.0
ground LiAl(NH2)4-LiAlH4 (1:3)
1.5
1.0
0.5
0.0
-0.5
0.0
LiAl(NH2)4
-0.5
-1.0
-1.5
0
50
100
150
200
250
300
Temperature (oC)
Figure 6. DSC measurement of ground LiAl(NH2)4-LiAlH4 (1:3) and self-made LiAl(NH2)4.
3.4 Comparison of LiH, LiBH4 and LiAlH4 in the interaction with LiAl(NH2)4
LiH essentially shows ionic interaction between Li and H with finite charge transfer from Li to H. LiBH4

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and LiAlH4, on the other hand, consist of ionic interaction between Li+ and XH4 (X = B, Al) and covalent
-
-
interaction between X and H. Hydrogen in MH4 is covalently bonded to central X in tetrahedral geometry with
relatively smaller amount of charge transfer to H than that in LiH. The amount of charge transfer to H further
varies with the Pauling electronegativity of the X element. For instances, the Pauling electronegativity of Al is
-
lower than B (1.61 vs 2.04), thus the amount of charge transfer to H is more from Al in AlH4 than that from B
in BH4 , making the hydride in LiAlH4 a stronger base. In LiBH4, a lower electron density on Hδ- resulted in
-
Li2Al(ND2)4BH4 rather than dehydrogenation when LiAl(ND2)4 was introduced [12]. This compound
-
-
decomposed in a stepwise manner, releasing ND3 from the Al(ND2)4 unit and H2 from BH4 unit in
Li2Al(ND2)4BH4, separately. In contrast, when a higher basicity hydride such as LiAlH4 or LiH [21] was
employed, it reacted with LiAl(NH2)4 to release H2 at much lower temperatures. In current study, due to the
presence of the oppositely charged atoms in LiAl(NH2)4-LiAlH4 system, it is plausible to ascribe the strong
electrostatic attractions of Hδ+···Hδ- as the driving forces for the dehydrogenation to occur at low temperatures.
On the other hand, we cannot rule out the driving force from strong donor-acceptor attraction between Al in
LiAlH4 and N in ternary amide.
4.0
Conclusion
In this study, we have investigated the interaction of LiAl(NH2)4-LiAlH4 via mechanical milling and
thermal method. The results indicate that interaction of LiAl(NH2)4 and LiAlH4 is an energy viable process at
ambient condition, releasing 70 % of the hydrogen (6 equiv. of H2 or 5.7 wt% H2) within 2 hours of
mechanical milling. During the mechanical milling, the rate of dehydrogenation increased with increasing
amount of LiAlH4, indicating that the dehydrogenation mechanism is prone to ion migration over NH3
mediation. In the ground LiAl(NH2)4-LiAlH4 (1:3) when the starting materials are not in intimate contact, NH3
mediated dehydrogenation is prone to occur. However, in the current study, the NH3 released from LiAl(NH2)4
did not trigger the interaction with LiAlH4. Instead, the decomposed residue, LiAl(NH)2 reacted with LiAlH4
and resulted in rapid release of hydrogen. It is also important to note that hydride with higher basicity is
required to trigger amide-hydride interaction to achieve dehydrogenation at low temperatures.

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Acknowledgement
Y.S. Chua would like to acknowledge the financial support from USM Short Term Grant
(304/PKIMIA/6313210). G. Wu and P. Chen also thank the Project of National Science Funds for Distinguish
Young Scholars (51801197) and Sino-Japanese Research Cooperative Program of Ministry of Science and
Technology (2016YFE0118300) for financial support.
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Highlights
•
•
•
Large amount of H2 can be released from LiAl(NH2)4–LiAlH4 system upon milling
H2 release is prone to ion migration mechanism in mechanical milling
NH3 mediated H2 release would occur in homogenously ground sample during
heating
•
Hydride with higher basicity is required to induce H2 release at low temperatures