Promoted hydrogen release from ammonia borane with mannitol via a solid-state reaction route

Article abstract of DOI:10.1039/c1dt11567g

Promoted hydrogen release from ammonia borane (NH₃BH ₃, AB) with mannitol (C₆H₈(OH)₆, MA) additive is reported. It is found that for the MA/2AB sample, the dehydrogenation temperature is lowered by ～25 °C compared to that of neat AB, the liberation of undesired byproduct borazine is suppressed, and the released ammonia can be removed by using anhydrous MgCl₂ as absorber. The analyses of Raman, Fourier transform infrared spectroscopy and ¹¹B nuclear magnetic resonance spectroscopy demonstrate the breaking of B-N, B-H and O-H bonds and the formation of B-O bonds for the dehydrogenation process of MA/2AB. These results suggest a solid-state dehydrogenation reaction between AB and MA: the B-H^δ- bonds in AB and the O-H ^δ+ bonds in MA combine with each other to release H ₂. Furthermore, the use of the perfect -OH carrier MA as additive leads to a straightforward understanding of the improved dehydrogenation of AB under the effect of hydroxyl groups in the solid state.

Full text of DOI:10.1039/c1dt11567g

View Article Online / Journal Homepage / Table of Contents for this issue
Dynamic Article Links
Dalton
Transactions
Cite this: Dalton Trans., 2012, 41, 871
www.rsc.org/dalton
PAPER
Promoted hydrogen release from ammonia borane with mannitol via a
solid-state reaction route
Yuede Pan, Yan Wang, Yanliang Liang, Zhanliang Tao and Jun Chen*
Received 20th August 2011, Accepted 2nd October 2011
DOI: 10.1039/c1dt11567g
Promoted hydrogen release from ammonia borane (NH3BH3, AB) with mannitol (C6H8(OH)6, MA)
additive is reported. It is found that for the MA/2AB sample, the dehydrogenation temperature is
lowered by ~25 ◦C compared to that of neat AB, the liberation of undesired byproduct borazine is
suppressed, and the released ammonia can be removed by using anhydrous MgCl2 as absorber. The
analyses of Raman, Fourier transform infrared spectroscopy and 11B nuclear magnetic resonance
spectroscopy demonstrate the breaking of B–N, B–H and O–H bonds and the formation of B–O bonds
for the dehydrogenation process of MA/2AB. These results suggest a solid-state dehydrogenation
reaction between AB and MA: the B–Hd- bonds in AB and the O–Hd+ bonds in MA combine with each
other to release H2. Furthermore, the use of the perfect –OH carrier MA as additive leads to a
straightforward understanding of the improved dehydrogenation of AB under the effect of hydroxyl
groups in the solid state.
the thermolysis of AB in the solid state, a perfect –OH carrier is
Introduction
needed.
Ammonia borane (NH3BH3, AB) has attracted much attention in
Herein we report that the polyol mannitol (C6H8(OH)6, MA),
the past decade as a promising hydrogen storage material, owing
which contains six –OH groups in each molecule, promotes the
to its extremely high hydrogen content (19.6 wt%) and moder-
dehydrogenation properties of AB. Our results show that the
ate decomposition temperature.1–3 Indeed, neat AB can release
addition of MA lowers the dehydrogenation temperature and
hydrogen via a multi-step decomposition process.4 However, the
suppresses the release of borazine. The improved performance
can be ascribed to the chemical reaction between the –OH groups
in MA and the –BH3 groups in AB.
practical onboard application of AB has been retarded by its
sluggish dehydrogenation kinetics under 100 ◦C and the liberation
of detrimental volatile byproducts (e.g., borazine B3N3H6).
To solve these problems, several approaches have been applied
Experimental
to improve the dehydrogenation properties of AB such as through:
(1) catalyzed hydrolysis or methanolysis;5–7 (2) catalyzed hydrogen
Ammonia borane (NH3BH3, AB, 97%, MW = 30.87, Aldrich),
mannitol (C6H8(OH)6, MA, 98%, MW = 182.17, Alfa) and
desorption under nonprotic conditions;8 and (3) thermolysis
of AB aided by metal cation substitution,9,10 additives,11,12 and
anhydrous magnesium chloride (MgCl2, 99%, Alfa) were used
scaffolds.13,14 Compared to the former two solid–liquid reaction
as received without further purification. Mannitol is a white
systems, the latter solid–gas method is more appreciated for
crystalline organic compound; it is a sugar alcohol, as well as a
practical onboard applications owing to the simplicity of ap-
polyol. Compared with the simplest alcohol (i.e., methanol) in the
paratus design and the available hydrogen capacity advantage.15
liquid state, mannitol is a solid-state alcohol with a melting point
Examples of the scaffolds that have been used to confine AB
of 166 ◦C. The MA/xAB mixtures with various molar ratios (x =
6, 3, and 2) were obtained by using a grinding method under an
include several kinds of porous silica and carbon materials.16–20 For
these materials, however, besides the nanoconfinement effect, the
argon atmosphere. In a typical experiment, 40 mg of the MA/2AB
surface hydroxyls also contribute to the improved dehydrogenation
mixture was ground for 15 min using a mortar and pestle in an
behaviours of the incorporated AB. This combined action leads
argon-filled glove box.
to a vague interpretation of the function of the hydroxyl groups.
The X-ray diffraction (XRD) patterns of the samples were
Therefore, to better understand the effect of hydroxyl groups on
obtained on a Rigaku D/max 2500 X-ray diffractometer using
Cu-Ka radiation at a scanning rate of 8◦ min-1. Temperature
programmed desorption/mass spectrometry (TPD/MS) experi-
Institute of New Energy Material Chemistry and Key Laboratory of
ments were performed on an Autosorb-1 C with a Prismaplus
Advanced Energy Materials Chemistry (Ministry of Education), Chemistry
QME 220 MS detector (Quantachrome, USA) under Ar gas flow
College, Nankai University, Tianjin, 300071, China. E-mail: chenabc@
nankai.edu.cn; Fax: +86-22-23506808; Tel: +86-22-23506808
◦
with a heating rate of 2 C min-1. Thermogravimetry (TG) and
This journal is
The Royal Society of Chemistry 2012
Dalton Trans., 2012, 41, 871–875 | 871
©

View Article Online
differential scanning calorimetry (DSC) curves were acquired in a
simultaneous thermoanalyzer system TA-SDTQ600 under a N2
◦
atmosphere at a ramping rate of 5 C min-1. Raman spectra
were collected on a confocal Raman microscope (DXR, Thermo
Fisher Scientific) using the 532 nm line from an argon-ion laser
at a power level of 10 mW. Fourier transform infrared spectra
(FTIR) data were acquired by using an FTIR-650 spectrometer
(Tianjin Gangdong) at a resolution of 4 cm-1. Solid-state 11B MAS
NMR experiments were conducted in a Varian InfinityPlus-400
spectrometer (9.47 T) at a frequency of 128.24 MHz, using a
2.5 mm 2-Ch CPMAS probe. For the Bloch decay experiment, a
50 kHz spin width, a 0.3 ms pulse width for 11B without decoupling,
and a pulse delay of 6 s were used. All the 11B chemical shifts were
referenced to NaBH4 (-41 ppm).
Results and discussion
Fig. 1 shows the XRD patterns of MA, MA/xAB (x = 2, 3 and 6)
and AB. For the prepared samples. The diffraction peaks of both
MA and AB can be clearly identified, with essentially no change
in the peak positions and symmetry. This reveals that the phase
stability of the raw materials is sustained during the preparation
process, which means that the applied grinding method can avoid
the subsidiary reactions found in the ball-milling method or the
solvent-based mixing method.18,21
Fig. 2 TPD/MS profiles of AB, MA/6AB, MA/3AB and MA/2AB
◦
at a heating rate of 2 C min-1. Each sample contains 2.0 mg of AB. No
diborane (m/z = 27) is detected for all the four samples under our detection
limit.
Table 1 Summary of the data from the MS curves in Fig. 2
Sample
To/H2
T
p1/H2
T
p2/H2
To/B3N3H6
To/NH3
Neat AB
MA/6AB
MA/3AB
MA/2AB
106
84
83
120
98
101
96
159
121
119
123
124
124
124
110
113
99
80
To = onset temperature; Tp1 = the first-peak temperature; Tp2 = the second-
peak temperature; the unit for these data is degree Celsius (◦C).
Fig. 1 XRD patterns of MA, MA/2AB, MA/3AB, MA/6AB and AB
with the molecular structure of mannitol (MA) shown in the upper right.
Fig. 2 presents a comparison of the thermal decomposition
properties of AB and MA/xAB (x = 6, 3 and 2) by employing
TPD/MS. Neat AB starts to release hydrogen at 106 ◦C via a
two-step process with dehydrogenation peaks centered at 120 ◦C
amounts of borazine start to be liberated at 124 ◦C, while no
ammonia gas is detected. In contrast, the release of borazine is
suppressed partially for MA/xAB (x = 6 and 3) and completely
for MA/2AB. However, ammonia appears for the MA/xAB (x =
6 and 3) samples, and its onset temperature decreases and the
quantity increases obviously for the MA/2AB. For comparison
purposes, the onset and peak temperatures of the released gases
for the four samples are listed in Table 1.
Through a more careful examination, we find that there exists a
regular pattern for the gas release behaviours of the four samples.
As shown in Fig. 2, with the increase of the molar ratio of MA to
AB gradually from 0 to 1 : 2, hydrogen release (<110 ◦C) increases,
borazine release decreases, and ammonia release increases. To
◦
and 159 C, respectively, agreeing well with the literature.22 In
contrast, the MA/xAB (x = 6, 3 and 2) samples show ~20 ◦C
lower onset temperatures of dehydrogenation. The first and second
dehydrogenation peaks are centered at ~100 ◦C and ~120 ◦C,
respectively, which are ~20 ◦C and ~40 ◦C lower than those of
neat AB. In addition, compared to MA/6AB and MA/3AB,
the MA/2AB sample shows much stronger first-peak intensity
and lower onset and first-peak temperatures for dehydrogenation.
Concurrent with the release of hydrogen for neat AB, large
872 | Dalton Trans., 2012, 41, 871–875
This journal is
The Royal Society of Chemistry 2012
©

View Article Online
explain this phenomenon, further characterizations are needed
and the discussion will be presented later.
Therefore, as can be seen from Fig. 2 and Table 1, the
MA/2AB exhibits excellent dehydrogenation properties and com-
plete suppression of borazine release. The improved performance
of MA/2AB may arise from the hydroxyl groups in MA,
which possibly act as catalysts or participate as reactants in the
thermolysis reaction of AB.18–20
Fig. 3 shows the synchronous TG/DSC results for AB and
MA/2AB. The TG curve of neat AB clearly shows that the
decomposition starts at ~110 ◦C followed by a two-step weight
loss process, which is consistent with the MS result for hydrogen
(m/z = 2) released from AB in Fig. 2. The total mass loss of
AB is 60 wt%, which is much higher than the expected value of
13 wt% for the two equivalents of H2 released from AB. This
severe mass loss suggests that, besides the hydrogen liberation,
large amounts of borazine are released from AB, as can also be
seen qualitatively from Fig. 2. For the DSC curve of neat AB,
◦
a sharp endothermic melting peak at 117 C is followed by two
exothermic peaks centered at 124 ◦C and 163 ◦C, which correspond
to the first and second dehydrogenation steps, respectively. The TG
curve of the MA/2AB sample sho◦ws that the distinguishable onset
Fig. 4 Raman spectra of AB, MA, MA/2AB before heating and
MA/2AB after heating at 110 ◦C for 15 min (from top to bottom). (a)
N–H stretching for AB and O–H stretching for MA; (b) B–H stretching
for AB; and (c) B–N stretching for AB.
◦
temperature of weight loss is 90 C, which is ~20 C lower than
that of neat AB. The mass loss for the MA/2AB sample is 18.9%,
which accounts for the release of both hydrogen and ammonia. For
the DSC curve of the MA/2AB sample, a strong exothermic peak
at 104 ◦C and a weak one at 124 ◦C are present, corresponding to
the two dehydrogenation peaks for MA/2AB as shown in Fig. 2.
As determined from the DSC results, the decomposition reaction
enthalpy (DH) for the MA/2AB is -89 kJ mol-1 NH3BH3, which
is much higher than that of neat AB (DH = -21 kJ mol-1).23 This
greater exothermicity for MA/2AB suggests that the hydroxyl
groups in MA may react with AB to form products with B–O
bonds.18 To further reveal the dehydrogenation mechanism of the
MA/2AB sample, spectroscopic studies were performed.
and bands at 794 cm-1, 779 cm-1 and 724 cm-1 to B–N stretching
(Fig. 4c).24,25 The spectrum of MA exhibits O–H stretching modes
for the band between 3400 cm-1 and 3200 cm-1 (Fig. 4a). The
MA/2AB sample exhibits a combination of the spectra of AB
and MA with peak intensities decreased. However, for the post-
heating MA/2AB, all the bands for N–H, O–H, B–H and B–N
vanish or weaken extremely. The disappearance of N–H and B–
N bonds agrees well with the release of NH3 from MA/2AB,
indicating that B–N bonds are broken down and –NH3 groups are
released as gaseous molecules of ammonia. The disappearance or
decrease of O–H and B–H bonds is in good agreement with the
release of H2. Protic O–H bonds and hydridic B–H bonds may
combine with each other to release hydrogen and form nonvolatile
products with B–O bonds. To demonstrate the existence of B–O
bonds in the post-heating products of MA/2AB, we performed
FTIR and solid-state 11B MAS NMR analyses.
Fig. 5 shows the FTIR spectra of MA, AB, MA/2AB before
heating and MA/2AB after heating. The spectrum for AB corre-
sponds well with the literature results.26 The MA/2AB exhibits N–
H stretching and O–H stretching for the band between 3500 cm-1
and 3100 cm-1, which becomes a broad bulge for the post-heating
products, indicating the decrease of the N–H and O–H bonds.
The band between 2400 cm-1 and 2100 cm-1 for B–H bonds in the
MA/2AB sample becomes narrower and weaker after heating,
which confirms the decrease of B–H bonds. For the post-heating
MA/2AB, the peaks at 2747 cm-1 and 1437 cm-1 are ascribed to C–
H stretching and bending, respectively, and the peak at 1047 cm-1
can be assigned to C–O stretching. It is worthwhile to note that
an obvious peak appears at 654 cm-1, which can be assigned to
the Raman inactive BO3 bending vibration.27 Interestingly, this
significant finding consists very well with the B/O atomic ratio
of MA/2AB (i.e., 1 : 3), which means that the overall reaction
between AB and MA may be a stoichiometric process. In other
words, for the thermal decomposition of MA/2AB, each NH3BH3
Fig. 3 TG/DSC results of neat AB and MA/2AB at a heating rate of
5 ◦C min-1. TG: solid line; DSC: dashed line.
Fig. 4 shows the Raman spectra of AB, MA, MA/2AB
before heating and MA/2AB after heating. The spectrum of
AB is in good agreement with the literature data: the bands at
3313 cm-1, 3251 cm-1 and 3172 cm-1 are assigned to N–H stretching
(Fig. 4a); 2377 cm-1 and 2282 cm-1 to B–H stretching (Fig. 4b);
This journal is
The Royal Society of Chemistry 2012
Dalton Trans., 2012, 41, 871–875 | 873
©

View Article Online
Table 2 Quantitative analyses of the four samples in Fig. 2
Sample
MA : AB
Eqn (1)
Eqn (2)
Neat AB
MA/6AB
MA/3AB
MA/2AB
0
0
1
1 : 6
1 : 3
1 : 2
1/3
2/3
1
2/3
1/3
0
The last two columns show the calculated proportions of AB that take
part in eqn (1) and eqn (2), respectively.
which are composed of different numbers of carbon skeletons of
MA linked by B–O bonds.
Based on the results that (1) H2 and NH3 gases were released
(TPD/MS); (2) the weight loss was 18.9 wt% (TG/DSC); and (3)
O–H, B–H and B–N bonds were broken down and B–O bonds
were formed after heating (Raman, FTIR and 11B NMR), the
overall dehydrogenation reaction for the MA/2AB sample can be
expressed by eqn (1).
Fig. 5 FTIR spectra of MA, AB, MA/2AB before heating and MA/2AB
after heating at 110 ◦C for 15 min.
0.5 C6H8(OH)6 + NH3BH3 → 0.5/n (C6H8O6B2)n + 3 H2↑ +
(1)
NH3↑
molecule reacts with three –OH groups to form products with BO3
bonding structure.
In this reaction, –OH groups in MA interact with NH3BH3
to produce H2, NH3 and nonvolatile products with B–O bonds,
which is consistent with the significantly greater exothermicity
(DH = -89 kJ mol-1) than that of neat AB (DH = -21 kJ mol-1).18
It is also shown that the released H2 originates from both the
–OH groups in MA and the –BH3 groups in AB. Since the B
atoms are immobilized by the –OH groups to form B–O bonds,
the release of borazine is thus suppressed. Furthermore, as a result
of the formation of thermodynamically stable B–O bonds, the B–N
bonds are broken down and ammonia is released.19
To further confirm the formation of B–O bonds, solid-state 11
MAS NMR experiments were performed. Fig. 6 presents the 11
B
B
NMR spectra of AB, MA/2AB before heating and MA/2AB
after heating. It is noted that the 11B NMR spectra of MA/2AB
and AB are almost the same, indicating that no chemical reaction
happens between MA and AB during the preparation process. The
peak centered at -26.9 ppm can be assigned to AB, while the side
peak at -24.7 ppm probably originates from an impurity in the
commercial AB.25 For the post-heating MA/2AB, three peaks are
observed to center at 6.5, 11.1 and 14.5 ppm, respectively, which
can be assigned to B–O bonds.18 The B–O bonds may be formed
through the reaction between the B–H bonds in NH3BH3 and the
O–H bonds in C6H8(OH)6. As there are three B–H bonds in AB
and six O–H bonds in MA, each AB molecule may react with as
many as three MA molecules while each MA molecule can react
with up to six AB molecules. Therefore, the thermolysis products
of the MA/2AB sample may consist of different-sized molecules,
Note that MA/2AB decomposes according to eqn (1), the
pyrolysis of neat AB can be expressed by eqn (2).
NH3BH3 → H2↑ + N3H3B6↑ + NxByHz
(2)
On the basis of eqn (1) and (2), the relationship between the
gas release behaviour and the molar ratios of MA to AB can be
interpreted. First, we should note that each of the four samples
contains the sam◦e amount of AB (i.e. 2.0 mg). Neat AB releases
hydrogen (>110 C) and borazine; MA/2AB liberates hydrogen
and ammonia. To explain the gas release behaviour of MA/6AB
and MA/3AB more clearly, we suppose that the component of AB
in these two samples participates in either reaction (1) or reaction
(2), though the actual reaction processes may be more complicated.
According to the quantitative analysis results (Table 2) of the four
samples, with the molar ratio of MA to AB increasing gradually
from 0 to 1 : 2, more and more AB participa◦tes in reaction (1),
which causes the increase in hydrogen (<110 C) and ammonia;
meanwhile, less and less AB participates in reaction (2), which
leads to the decrease in borazine.
For the MA/xAB system, though the release of borazine is
suppressed, another kind of detrimental gas, ammonia, appears.
Especially for the sample of MA/2AB, the large amount of
released ammonia is obviously a drawback. To get rid of it,
anhydrous MgCl2 was used as an ammonia absorber, and the
TPD/MS result (Fig. 7) of the MA/2AB sample showed that
ammonia was successfully removed. Christensen et al.28 reported
Mg(NH3)6Cl2 in combination with an ammonia decomposition
catalyst as an intriguing hydrogen storage material. Anhydrous
Fig. 6 11B MAS NMR spectra of AB, MA/2AB before heating and
MA/2AB after heating at 110 ◦C for 15 min.
874 | Dalton Trans., 2012, 41, 871–875
This journal is
The Royal Society of Chemistry 2012
©

View Article Online
Notes and references
1 F. H. Stephens, V. Pons and R. T. Baker, Dalton Trans., 2007, 2613–
2626.
2 B. Peng and J. Chen, Energy Environ. Sci., 2008, 1, 479–483.
3 A. Staubitz, A. P. M. Robertson and I. Manners, Chem. Rev., 2010,
110, 4079–4124.
4 M. G. Hu, R. A. Geanangel and W. W. Wendlandt, Thermochim. Acta,
1978, 23, 249–255.
5 M. Chandra and Q. Xu, J. Power Sources, 2006, 156, 190–194.
6 F. Y. Cheng, H. Ma, Y. M. Li and J. Chen, Inorg. Chem., 2007, 46,
788–794.
7 P. V. Ramachandran and P. D. Gagare, Inorg. Chem., 2007, 46, 7810–
7817.
8 M. Ka¨b, A. Friedrich, M. Drees and S. Schneider, Angew. Chem., Int.
Ed., 2009, 48, 905–907.
9 Z. T. Xiong, C. K. Yong, G. T. Wu, P. Chen, W. Shaw, A. Karkamkar,
T. Autrey, M. O. Jones, S. R. Johnson, P. P. Edwards and W. I. F. David,
Nat. Mater., 2008, 7, 138–141.
10 X. Kang, J. Luo, Q. Zhang and P. Wang, Dalton Trans., 2011, 40,
3799–3801.
11 J. Luo, X. Kang, Z. Fang and P. Wang, Dalton Trans., 2011, 40, 6469–
Fig. 7 TPD/MS profiles of MA/2AB using anhydrous MgCl2 as
6474.
ammonia absorber.
12 T. He, Z. T. Xiong, G. T. Wu, H. L. Chu, C. Z. Wu, T. Zhang and P.
Chen, Chem. Mater., 2009, 21, 2315–2318.
13 J. Z. Zhao, J. F. Shi, X. W. Zhang, F. Y. Cheng, J. Liang, Z. L. Tao and
J. Chen, Adv. Mater., 2010, 22, 394–397.
14 Z. Li, G. Zhu, G. Lu, S. Qiu and X. Yao, J. Am. Chem. Soc., 2010, 132,
1490–1491.
15 T. B. Marder, Angew. Chem., Int. Ed., 2007, 46, 8116–8118.
16 A. Gutowska, L. Y. Li, Y. S. Shin, C. M. M. Wang, X. H. S. Li, J. C.
Linehan, R. S. Smith, B. D. Kay, B. Schmid, W. Shaw, M. Gutowski
and T. Autrey, Angew. Chem., Int. Ed., 2005, 44, 3578–3582.
17 A. Feaver, S. Sepehri, P. Shamberger, A. Stowe, T. Autrey and G. Cao,
J. Phys. Chem. B, 2007, 111, 7469–7472.
MgCl2 was used to absorb NH3 to produce Mg(NH3)6Cl2, which
could release NH3 under heating and regenerate MgCl2 mean-
while. Thus, in combination with MgCl2, MA/2AB is a promising
solid hydrogen storage medium with improved dehydrogenation
properties compared to neat AB.
Conclusions
18 S. Sepehri, A. Feaver, W. J. Shaw, C. J. Howard, Q. Zhang, T. Autrey
and Cao, J. Phys. Chem. B, 2007, 111, 14285–14289.
19 L. Li, X. Yao, C. H. Sun, A. J. Du, L. N. Cheng, Z. H. Zhu, C. Z. Yu,
J. Zou, S. C. Smith, P. Wang, H. M. Cheng, R. L. Frost and G. Q. M.
Lu, Adv. Funct. Mater., 2009, 19, 265–271.
20 T. Zhang, X. Yang, S. Yang, D. Li, F. Cheng, Z. Tao and J. Chen, Phys.
Chem. Chem. Phys., 2011, 13, 18592–18599.
21 Q. Zhang, C. Tang, C. Fang, F. Fang, D. Sun, L. Ouyang and M. Zhu,
J. Phys. Chem. C, 2010, 114, 1709–1714.
22 S. F. Li, Y. H. Guo, W. W. Sun, D. L. Sun and X. B. Yu, J. Phys. Chem.
C, 2010, 114, 21885–21890.
The MA/2AB sample exhibits lowered dehydrogenation tem-
perature and suppression of borazine release compared to neat
AB. These major improvements can be ascribed to the chemical
reaction between the B–H bonds in AB and the O–H bonds in
MA to release H2 and form B–O bonds. In this work, the use
of a perfect –OH carrier (i.e., MA) as additive allows a better
understanding of the effect of hydroxyl groups on AB to promote
the solid-state thermal decomposition properties. Interestingly, in
combination with MgCl2 as an ammonia absorber, MA/2AB is a
promising solid hydrogen storage medium.
23 G. Wolf, J. Baumann, F. Baitalow and F. P. Hoffmann, Thermochim.
Acta, 2000, 343, 19–25.
24 N. J. Hess, M. E. Bowden, V. M. Parvanov, C. Mundy, S. M. Kathmann,
G. K. Schenter and T. Autrey, J. Chem. Phys., 2008, 128, 034508.
25 X. Kang, L. Ma, Z. Fang, L. Gao, J. Luo, S. Wang and P. Wang, Phys.
Chem. Chem. Phys., 2009, 11, 2507–2513.
Acknowledgements
TG/DSC experiments were conducted by R. Ji, the senior
experimentalist from Hebei University of Technology. This work
was supported by the National Research Programs of MOST
(2009AA03Z224, 2009CB220003 and 2010CB631301), MOE In-
novation Team (IRT0927), Tianjin High-Tech (10SYSYJC27600)
and the Fundamental Research Funds for the Central universities.
26 J. Baumann, F. Baitalow and G. Wolf, Thermochim. Acta, 2005, 430,
9–14.
27 R. R. Servoss and H. M. Clark, J. Chem. Phys., 1957, 26, 1179–
1184.
28 C. H. Christensen, R. Z. Sorensen, T. Johannessen, U. J. Quaade, K.
Honkala, T. D. Elmoe, R. Kohler and J. K. Norskov, J. Mater. Chem.,
2005, 15, 4106–4108.
This journal is
The Royal Society of Chemistry 2012
Dalton Trans., 2012, 41, 871–875 | 875
©