Facile synthesis of anhydrous alkaline earth metal dodecaborates MB12H12 (M = Mg, Ca) from M(BH4)2

Article abstract of DOI:10.1039/c5dt02343b

Metal dodecaborates M_2/nB₁₂H₁₂ are among the dehydrogenation intermediates of metal borohydrides M(BH₄)_n with a high hydrogen density of approximately 10 mass%, the latter is a potential hydrogen storage material. There is therefore a great need to synthesize anhydrous M_2/nB₁₂H₁₂ in order to investigate the thermal decomposition of M_2/nB₁₂H₁₂ and to understand its role in the dehydrogenation and rehydrogenation of M(BH₄)_n. In this work, anhydrous alkaline earth metal dodecaborates MB₁₂H₁₂ (M = Mg, Ca) have been successfully synthesized by sintering M(BH₄)₂ (M = Mg, Ca) and B₁₀H₁₄ in a stoichiometric molar ratio of 1 : 1. Thermal decomposition of MB₁₂H₁₂ shows multistep pathways with the formation of H-deficient monomers MB₁₂H_12-x containing icosahedral B₁₂ skeletons and is followed by the formation of (MB_yH_z)_n polymers. Comparison of the thermal decomposition of MB₁₂H₁₂ and M(BH₄)₂ suggests different behaviours of the anhydrous MB₁₂H₁₂ and those formed from the decomposition of M(BH₄)_n.

Full text of DOI:10.1039/c5dt02343b

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DOI: 10.1039/C5DT02343B
Graphical abstract
Thermal decomposition of MB12H12 (M=Mg, Ca) forms H-deficient monomers MB12H
12-x
containing icosahedral B12 skeletons and followed by the formation of (MB
y z n
H ) polymers.
MgB H
1
2
12
1
1
B MAS NMR
H-deficient
monomers
MgB H
12-x
ω = 16kHz
12
2
4
00 ºC
00 ºC
Polymers
(MgB H )
y
z n
7
00 ºC
00 ºC
8
3
0
20 10
0
ppm
-10 -20 -30
Amorphous B

Ple aDs ea l dt oo nn To rt a and sj ua sc tt imo na sr gins
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DOI: 10.1039/C5DT02343B
Dalton Transactions
PAPER
Facile Synthesis of Anhydrous Alkaline Earth Metal Dodecaborate
MB H (M = Mg, Ca) from M(BH )
12
12
4 2
Received 00th January 20xx,
Accepted 00th January 20xx
a
*b,c
d
d
a,b,c
Liqing He, Hai-Wen Li, Nikolay Tumanov, Yaroslav Filinchuk, Etsuo Akiba
DOI: 10.1039/x0xx00000x
Metal dodecaborate M2/n
hydrogen density of approximately 10 mass%, the latter is a potential hydrogen storage material. It is therefore in great
need to synthesize anhydrous M2/n 12 in order to investigate the thermal decomposition of M2/n 12 and to
understand its role in the dehydrogenation and rehydrogenation of M(BH . In this work, anhydrous alkaline earth metal
dodecaborates MB12 12 (M = Mg, Ca) have been successfully synthesized by sintering of M(BH (M = Mg, Ca) and B10
with stoichiometric molar ratio of 1:1. Thermal decomposition of MB12 12 shows multistep pathways with the formation of
H-deficient monomers MB12 12-x containing icosahedral B12 skeletons and followed by the formation of (MB polymers.
Comparison on the thermal decomposition of MB12 suggests that different behaviours of the anhydrous
and those formed the decomposition of M(BH
12 4 n
B H12 is one of the dehydrogenation intermediates of metal borohydride M(BH ) with a high
www.rsc.org/
12
B H
12
B H
4 n
)
H
)
4 2
H
14
H
H
y z n
H )
H
12 and M(BH
from
4 2
)
MB12H
12
4 n
) .
decomposition of metal dodecaborate M2/nB12H , therefore, is
12
Introduction
Hydrogen, known as an environment-friendly energy carrier,
can be stored in chemical materials in the form of hydrides.
Among various kinds of hydrides, borohydrides with high
volumetric and gravimetric hydrogen densities such as LiBH (H
capacity: 18.5 mass% and 122 kg H /m ), Mg(BH ) (14.9
in great need to elucidate its role in the dehydrogenation and
rehydrogenation of borohydrides.
M2/nB H is generally synthesized using wet chemistry
12
12
processes, followed by a careful dehydration under vacuum
22, 23
slightly above 120 °C.
Higher temperatures cause the
4
3
hydrolysis, and lower do not allow to remove water
completely, thus failing in synthesizing some anhydrous
2
4 2
3
mass% and 147 kg H /m ) and Ca(BH ) (11.6 mass% and 124
2
4 2
24
3
alkaline earth metal dodecaborates such as MgB H . Under
1
2 12
kg H /m ), have been considered as potential hydrogen
2
1-4
such condition, we have recently developed a novel solvent-
free synthesis method, i.e. sintering of M(BH ) with B H , by
storage materials. Most of borohydrides show a stepwise
decomposition accompanied with formation of
intermediates containing polyanions, such as [B H ] , [B H ]
4
n
10 14
a
2
-
-
which high purity anhydrous alkali metal dodecaborates
2
6
3
8
25
2
-
M B H (M=Li, Na, K) have been successfully synthesized.
2
12 12
and/or [B H ] . The decomposition mechanism significantly
1
2 12
In this work, we have applied our recently developed
-17 sintering process to the syntheses of anhydrous alkaline earth
metal dodecaborates MgB H and CaB H . Anhydrous
depends on the dehydrogenation temperature and hydrogen
backpressure as well as the particle size of borohydrides.
5
2-
1
2
12
12 12
The intermediates containing small clusters like [B H ] and
2
6
-
MB H have been successfully synthesized by sintering of
12 12
[
B H ] were found to be beneficial for the rehydrogenation to
3 8
1
3, 16, 18
2- Mg(BH ) and Ca(BH ) with B H , based on the equation (1):
4 2 4 2 10 14
12
the corresponding borohydrides.
The [B H ]
12
M(BH ) + B H
→
MB12H12 + 5H (M = Mg, Ca)
(1)
4
2
10 14
2
intermediate, despite its formation is still controversial, having
strong B-B bonds in a stable icosahedral boron cage, has been
widely regarded as an obstacle for the rehydrogenation to
Thermal decomposition behaviours of the thus synthesized
anhydrous MgB H and CaB12H12 were carefully investigated
1
2 12
7
, 10, 19-21
using thermogravimetry (TG), mass spectrometry (MS), X-ray
diffraction (XRD), Raman spectra and solid-state magic angle
spinning (MAS) nuclear magnetic resonance (NMR) spectra.
Furthermore, the decomposition processes of MgB H and
M(BH ) .
Fundamental investigation on the thermal
4
n
12 12
a.
b.
Department of Mechanical Engineering, Faculty of Engineering, Kyushu
University, Fukuoka 819-0395, Japan.
International Research Center for Hydrogen Energy, Kyushu University, Fukuoka
CaB H are compared with those for products formed during
12 12
the dehydrogenation of Mg(BH ) and Ca(BH ) , in order to
4 2 4 2
elucidate their roles in the dehydrogenation of borohydrides.
8
19-0395, Japan. E-mail: li.haiwen.305@m.kyushu-u.ac.jp. Tel.: +81-92-802-3226.
Fax: +81-92-802-3235.
c.
WPI International Institute for Carbon-Neutral Energy Research (WPI-I2CNER),
Kyushu University, Fukuoka 819-0395, Japan.
Institute of Condensed Matter and Nanosciences, Université catholique de
Louvain, Louvain-la-Neuve 1348, Belgium.
d.
Experimental
†
Electronic Supplementary Information (ESI) available: MS spectra of Mg(BH
XRD patterns and Raman spectra of MgB12 12 and CaB12 12 heated to respective
temperatures. See DOI: 10.1039/x0xx00000x
4 2
) ,
Commercial B H (99%, Wako), γ-Mg(BH ) (95%, Aldrich) and
10
14
4 2
H
H
Ca(BH ) (95%, Aldrich) were all stored in a glove box under Ar
4 2
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gas and used without further purification. Starting materials of the high level of baseline due to the fluorescent effect.
View Article Online
DOI: 10.1039/C5DT02343B
Mg(BH4)2 + B10H14 and Ca(BH4)2 + B H were firstly Furthermore, no trace of O-H bond of water is observed in the
10
14
mechanically milled at room temperature using a planetary Raman spectra, which proves the successful synthesis of the
ball mill (Fritsch P-7) with 10 steel balls (7 mm in diameter) in a anhydrous MgB H .
1
2 12
3
hardened steel vial (30 cm in volume) under 0.1 MPa Ar for 5
Anhydrous CaB H is also synthesized by sintering of
12 12
h (15 min milling, 5 min pausing). Subsequently, the ball milled Ca(BH ) + B H at 380 °C for 2 h, its XRD and Raman data are
4
2
10 14
samples of Mg(BH ) + B H and Ca(BH ) + B H were shown in Figure 2. Three representative diffraction peaks at 2θ
4
2
10 14
4 2
10 14
sealed into stainless steel crucibles for sintering at 300 °C for 1 = 9.3°, 9.5° and 10.5° originating from CaB H with a
1
2 12
2
8
h and at 380 °C for 2 h, respectively.
monoclinic (C2/c) crystal structure, are clearly observed
Powder XRD patterns were recorded by Rigaku Ultima IV X- in the XRD patterns. An impurity with an unknown structure
ray diffractometer with Cu-Kα radiation, and the accelerating was indexed in the orthorhombic crystal system (a = 13.580(2),
voltage/ tube current were set as 40 kV/ 40 mA. The sample b = 12.264(1), c = 4.2495(4) Å) and our preliminary analysis
powders were placed on a glass plate sealed by Scotch tape to suggests space group symmetry Pcab or Pbab. Our in-situ
prevent exposure to air during the measurement. Powder XRD diffraction experiments show that the second crystalline phase
patterns of the as-synthesized MgB H were measured in a disappears from the diffraction pattern after heating to 400°C,
12 12
glass capillary, on MAR345 diffractometer, with Mo Kα see Figure 2c. In Raman spectra, vibration peaks assigned to B-
2
-
rotating anode generator and a focusing mirror. The H bending and stretching modes of [B H ] are observed at
12
12
29
-
1
synchrotron radiation powder XRD pattern for the as- 585, 751 and 2485, 2547 cm , respectively. No O-H vibration
synthesized CaB H was measured on the Materials Science peak of water is detected in Raman spectra, which indicates
1
2 12
Beamline X04SA at the Swiss Light Source (transmission the successful synthesis of the anhydrous CaB H .
12 12
geometry in capillary, MYTHEN detector, λ = 1.00117 Å). A
variable temperature experiment on the sample of CaB H
2 12
1
was carried out at the Materials Science Beamline X04SA, SLS,
using the wavelength of 0.77619 Å. The sample was loaded in
a glass capillary, and was heated in 20 °C steps from room
temperature to 400 °C, and then cooled down to the ambient
temperature. A number of diffraction patterns was collected at
each temperature point to follow both time and temperature
dependences of the transformations.
Raman spectra were obtained from RAMAN-11 VIS-SS
(Nanophoton) using a green laser with 532 nm wavelength.
Thermal decomposition was examined by TG with a heating
rate of 5 °C/min under a 200 ml/min flow of He gas. The gas
released during TG measurement was analysed by quadrupole
mass spectrometer coupled with TG. Solid-state MAS NMR
spectra were recorded using
a
Bruker Ascend-600
spectrometer at room temperature. NMR sample preparations
were always done in a glove box filled with purified Ar gas and
11
dry N gas was used for sample spinning. B MAS NMR spectra
2
were obtained at excitation pulses of 6.5 μs
with strong H decoupling pulses. B NMR chemical shifts
（π/2 pulse) and
1
11
were referenced to BF OEt (δ = 0.00 ppm).
3
2
Results and discussion
1
. Synthesis of anhydrous MgB H and CaB H
12 12 12 12
Figure 1 shows XRD pattern and Raman spectra of Mg(BH ) +
4
2
B H after sintering at 300 °C for 1 h. The observed broad
10 14
peak between 2θ = 3° and 15° (between 2θ = 10° and 18° using
Cu-Kα radiation as shown in Figure S1) is distinct from the
Figure 1. (a) XRD pattern (Mo Kα) and (b) Raman spectra of 5 h
starting materials of Mg(BH ) and B H , as well as the
4
2
10 14
ball milled Mg(BH ) + B H followed by sintering at 300 °C
4
2
10 14
2
6
amorphous Mg(BH ) , and could be ascribed to the formation for 1 h. Starting materials of Mg(BH ) and B H are also
4
2
4 2
10 14
of amorphous MgB H theoretically predicted by First- shown as references, asterisk indicates the systematic error.
1
2 12
2
7
principle Calculations. In the Raman spectra, two peaks
2
-
ascribed to B-H bending and stretching vibrations of [B H ]
1
2 12
-
1
are observed at 751 and 2569 cm , respectively, together with
2
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Journal Name
The successful syntheses of the anhydrous MgB H and
ARTICLE
12 12
View Article Online
DOI: 10.1039/C5DT02343B
11
CaB H are further proved by solid state B MAS NMR
12 12
spectra, shown in Figure 3. The main resonances at -15.0 and -
2
-
1
4.0 ppm are assigned to [B H ] in MgB H and CaB H ,
12 12 12 12 12 12
28 2- 8,
respectively. [B H ] (-28.3 ppm for Mg, -26.3 ppm for Ca),
1
0 10
30
-
27
[
BH ] (-41.9 ppm for Mg, -32.2 ppm for Ca) and unknown
4
phases (-6.0 and -46.3 ppm) are detected in the synthesized
MgB H and CaB12H12 samples as impurities. In addition, the
12 12
synthesized anhydrous MgB H and CaB12H12 samples display
12 12
homogenous yellow color, which is different from the white
starting materials. All the above mentioned results, therefore,
consistently indicate that sintering of metal borohydrides
M(BH ) with B H is a facile method to synthesize anhydrous
4
2
10 14
alkaline earth metal dodecaborates.
1
1
Figure 3. B MAS NMR spectra of synthesized samples from
M(BH ) + B H (M = Mg: 5 h ball milling followed by sintering
4
2
10 14
at 300 °C for 1 h; M = Ca: 5 h ball milling followed by sintering
at 380 °C for 2 h).
2
. Thermal decomposition of anhydrous MgB H and CaB H
12 12 12 12
(
1) MgB H
12 12
Thermal decomposition behaviour of the anhydrous MgB H
2 12
1
examined by TG and MS are shown in Figure 4. Only hydrogen
is detected by MS, indicating the weight loss upon heating is
originated from the dehydrogenation of MgB H . The
12 12
dehydrogenation starts at approximately 190 °C, reaching 5.6
mass% or approximately 77% of the theoretical hydrogen
content in MgB H when heated up to 800 °C. The
1
2 12
decomposition pathway is multistep, as shown in TG and MS
results.
In order to elucidate the decomposition pathway of
anhydrous MgB H , the sample was heated to fixed
12 12
temperatures and subsequently cooled down to room
temperature, and the changes were followed systematically by
1
1
XRD, Raman and solid state B NMR. The results are shown in
Figure S1 and Figure 5, respectively. When the temperature is
increased up to 200 °C, the main resonance at -15.0 ppm
attributed to MgB H becomes weak, while the peak
1
2 12
intensity for Mg(BH ) and MgB H impurities do not change
4
2
10 10
obviously. This indicates that the decomposition of MgB H
2 12
1
starts at 190 °C, prior to that of Mg(BH ) as shown in Figure S2.
4
2
When the temperature is increased up to 400 °C, the broad
diffraction peak between 2θ= 10° and 18° disappears, and the
-1
B-H stretching mode of MgB H at 2569 cm becomes almost
1
2 12
invisible, the main resonance of MgB H at -15.0 ppm
1
2 12
reduces significantly without any change in the chemical shift,
which consistently indicate that a major part of B-H bond in
2
-
the icosahedral [B H ] has been broken to release hydrogen.
1
2 12
The released amount reaches 2.1 mass% at 400 °C, suggesting
Figure 2. (a) Synchrotron XRD (λ = 1.00117 Å) pattern and (b)
Raman spectra of 5 h ball milled Ca(BH ) + B H followed by that the decomposition product is probably H-deficient
4
2
10 14
12
sintering at 380 °C for 2 h. Asterisk indicates the systematic MgB12
H12-x (x = 3.5) that keeps the icosahedral B12 skeletons.
error. (c) Rietveld refinement plot for CaB H at 60 °C after When the temperature is further increased to 500, 600 and
12 12
heating to 400 °C. Red crosses and black line show the
experimental and calculated data, respectively. Blue line is the
difference profile, and green marks indicate Bragg positions of
CaB H .
7
4
00 °C, the released amount of hydrogen reaches 3.2, 3.8 and
2-
.6 mass% and the major resonance of [B H ] at -15.0 ppm
12 12
shifts to -13.1, -9.4 and -5.6 ppm. It suggests that MgB H
2 12-x
continuously releases hydrogen accompanied with the
1
12 12
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polymerization of the icosahedral B skeletons and the It is worth emphasizing that the thermal decomposition
1
2
View Article Online
DOI: 10.1039/C5DT02343B
31, 32
formation of (MgB H ) polymers,
insoluble in water and behaviour of the synthesized MgB H is fairly different from
12 12
y
z n
DMSO. When the sample is heated up to 800 °C, the major that formed during the dehydrogenation of Mg(BH ) . The
4
2
resonance shifts to 0.9 ppm, indicating the formation of synthesized MgB H exhibits a lower decomposition onset
12 12
amorphous boron at 800 °C. The temperature is higher than temperature and a wider decomposition temperature range of
33
that (600 °C) reported for MgB H /Carbon nanocomposite,
190 ~ 800 °C than Mg(BH ) . Also, the synthesized MgB H
4 2 12 12
12
12
suggesting that the carbon nanocomposite may contribute to decomposes into amorphous boron rather than MgB formed
2
34
the reduction of the decomposition temperature.
as the decomposition product from Mg(BH ) at 600 °C.
4 2
Based on the abovementioned experimental results, Taking into account the controversial discussions about the
thermal decomposition pathway of anhydrous MgB H could formation of MgB12H12 during the dehydrogenation of
12 12
be briefly summarized as the following steps:
Mg(BH ) , those differences may result from the following two
4 2
Step 1: MgB H →
2 12
MgB12H12-x + x/2H2
→ (MgB H ) + z’H
(2) possibilities: a) the concurrent formation of MgH2 and
(3) MgB H during the dehydrogenation of Mg(BH ) , since MgH2
1
Step 2: nMgB H
12
12-x
y
z n
2
12 12
4 2
Step 3: (MgB H )
→
amorphous B + Mg + z’’H2
(4)
facilitates the formation of MgB from MgB H as predicted
2 12 12
y
z n
9
by First-principles calculations; b) MgB H does not form as
1
2 12
a stable dehydrogenation intermediate of Mg(BH ) as
4
2
14
reported recently.
(
2) CaB H
1
2 12
Thermal decomposition behaviour of anhydrous CaB H is
12 12
systematically studied and the TG and MS results are shown in
Figure 6. Only hydrogen is detected by MS, indicating the
weight loss upon heating comes from the dehydrogenation of
CaB H . The dehydrogenation starts at ca. 320 °C and reaches
12 12
2
.5 mass% (approximately 38% of theoretical hydrogen
capacity in CaB H ), comparable to the reported value of 1.5
1
2 12
28
mass% at 600 °C. The reaction has multiple steps when
heated up to 750 °C.
11
The XRD patterns, Raman spectra and solid-state B MAS
NMR spectra of the anhydrous CaB H heated to fixed
12 12
temperatures and subsequently cooled down to room
temperature are shown in Figures S3 and 7, respectively.
When CaB H is heated up to 400 °C, no obvious changes of
12 12
Raman spectra and the major resonance for CaB H are seen,
12 12
Figure 4. TG curve and MS signals of the synthesized MgB H
2 12
1
whereas the diffraction peaks of the unknown phase and the
resonance at -32.2 ppm originates from the residual Ca(BH4)2
nearly disappears at 375 °C. This indicates that the weight loss
below 400 °C is responsible for the dehydrogenation of the
residual Ca(BH ) and the unknown phase, suggesting that the
(
mass numbers of 2 and 27 represent H and B H ).
2 2 6
4
2
impurities do not directly influence the decomposition of
CaB H . When CaB H is heated up to 500 °C, diffraction
12
12
12 12
peaks and Raman spectra attributed to CaB H disappear, the
1
2 12
major resonance at -14.0 ppm becomes significantly weaker
and overlaps with a broad resonance between 0 and -13 ppm,
suggesting that the dehydrogenation of CaB H to CaB12H12-x
12 12
as well as a polymerization of CaB H to water and DMSO
2 12-x
1
31, 32
insoluble (CaB H ) polymers starts close to 500 °C.
When
y
z n
CaB H is further heated up to 600 °C and 750 °C, the major
12 12
resonance shifts to -11.2 and -7.0 ppm, indicating the
continuous polymerization of (CaB H ) , similar to that of
y
z n
MgB H heated up to 500 ~ 700 °C. Unlike MgB H , no
12
12
12 12
obvious NMR spectra originated from amorphous boron is
observed when CaB H is heated up to 750 °C, whereas CaB6
12 12
has been demonstrated as the main dehydrogenation product
1
4, 20, 35
11
of Ca(BH ) above 330 °C.
4 2
Figure 5. B MAS NMR spectra of MgB H as synthesized and
1
2 12
heated up to respective temperatures.
4
| Dalton Trans., 2015, 00, 1-6
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Journal Name
ARTICLE
dodecaborates and metal borohydrides emphasize the
View Article Online
DOI: 10.1039/C5DT02343B
importance of systematic investigations of various possible
dehydrogenation intermediates and the corresponding metal
borohydrides, in order to determine the exact
dehydrogenation and rehydrogenation mechanisms for metal
borohydrides.
Conclusions
Anhydrous alkaline earth metal dodecaborates MgB H and
12 12
CaB H have been successfully synthesized through sintering
12 12
of ball milled M(BH ) + B H (M = Mg, Ca). This study again
4
2
10 14
proves that sintering of borohydrides with B H is a facile
10 14
method to synthesize anhydrous metal dodecaborates.
Systematic investigations of thermal decomposition
demonstrate that both MgB H and CaB12H12 firstly release
12 12
hydrogen to form H-deficient MB H with the icosahedral
12 12-x
Figure 6. TG curve and MS signals of the synthesized CaB H
1
2
12 B12 skeletons, followed by a polymerization process to produce
(MB H ) . The anhydrous MgB H is amorphous and it
(
mass numbers of 2 and 27 represent H and B H ).
2 2 6
y
z n
12 12
decomposes into amorphous boron at 800 °C, whereas
CaB H may require much higher temperature to complete
12 12
the decomposition. The lower electronegativity of Ca than that
of Mg is considered to be responsible for the higher stability of
3
6
CaB H than that of MgB H . On the other hand, thermal
12
12
12 12
decomposition of the synthesized MgB H and CaB H does
1
2
12
12 12
not seem directly correlate with the dehydrogenation of
Mg(BH ) and Ca(BH ) , suggesting the great importance of
4
2
4 2
further investigation on the correlation between
decomposition of possible dehydrogenation intermediates and
of the corresponding metal borohydrides.
Acknowledgements
We would like to sincerely thank Assoc. Prof. M. Yamauchi and
1
1
Asst. Prof. M. Watanabe in I2CNER for their great help on
B
MAS NMR measurement. This study was partially supported by
JSPS KAKENHI Grant Number 25709067, JSPS Invitation
Fellowship for Research in Japan (Short-Term), FNRS and the
International Institute for Carbon Neutral Energy Research
1
1
Figure 7. B MAS NMR spectra of CaB H as synthesized and
12 12
heated up to respective temperatures.
The decomposition pathway of the anhydrous CaB H is
briefly summarized as the following steps (below 750 °C):
Step 1 : CaB H
Step 2 : nCaB H
12 12
(WPI-I2CNER), sponsored by the Japanese Ministry of
Education, Culture, Sports, Science and Technology.
→
CaB H + x/2H2
→ (CaB H ) + z’H
y z n 2
(5)
(6)
1
2
12
12 12-x
1
2
12-x
Similar to that of MgB H , the decomposition behaviour of
12 12
Notes and references
the synthesized CaB H does not seem to directly correlate
1
2 12
1
.
S.-i. Orimo, Y. Nakamori, J. R. Eliseo, A. Züttel and C. M.
Jensen, Chemical Reviews, 2007, 107, 4111-4132.
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with the dehydrogenation of Ca(BH ) , suggesting that: a) CaH
2
4
2
forming in the decomposition of Ca(BH4)2 facilitates the
transformation of CaB H to produce CaB6 that is not
2
.
1
2 12
9, 28
detected when CaB H is heated even up to 750 °C;
or b)
12
12
3.
L. H. Rude, T. K. Nielsen, D. B. Ravnsbaek, U. Bösenberg,
M. B. Ley, B. Richter, L. M. Arnbjerg, M. Dornheim, Y.
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CaB H
2 12
does not form as a stable dehydrogenation
1
16
intermediate of Ca(BH ) as reported recently.
4
2
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12 12
CaB H reveal two steps of 1) dehydrogenation to produce H- 4.
H.-W. Li. J. Wang and Ping Chen, MRS Bulletin, 2013, 38,
12 12
4
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deficient MB H and 2) polymerization of MB12H12-x to form
1
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5
.
S.-I. Orimo, Y. Nakamori, N. Ohba, K. Miwa, M. Aoki, S.-i.
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(
MB H ) , which is the main step to form amorphous boron,
y z n
regarded as the major obstacle for rehydrogenation. The
uncorrelated thermal decomposition behaviours of metal
0
21920-021920-021923.
This journal is © The Royal Society of Chemistry 2015
Dalton Trans., 2015, 00, 1-6 | 5
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