In situ synthesized spherical nickel-silica composite particles for hydrolytic dehydrogenation of ammonia borane

Article abstract of DOI:10.1016/j.jallcom.2013.02.067

Spherical nickel-silica composite particles were synthesized by sol-gel based method in various solvents followed by in situ activation in aqueous sodium borohydride (NaBH₄)/ammonia borane (NH₃BH ₃) solutions. The resultin

Full text of DOI:10.1016/j.jallcom.2013.02.067

Journal of Alloys and Compounds 580 (2013) S313–S316
Contents lists available at SciVerse ScienceDirect
Journal of Alloys and Compounds
journal homepage: www.elsevier.com/locate/jalcom
In situ synthesized spherical nickel–silica composite particles for
hydrolytic dehydrogenation of ammonia borane
a,
⇑
b
a
Tetsuo Umegaki , Qiang Xu , Yoshiyuki Kojima
a
Department of Material & Applied Chemistry, College of Science & Engineering, Nihon University, 1-8-14, Kanda-Surugadai, Chiyoda-Ku, Tokyo 101-8308, Japan
National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577, Japan
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Available online 26 February 2013
Spherical nickel–silica composite particles were synthesized by sol–gel based method in various
solvents followed by in situ activation in aqueous sodium borohydride (NaBH
4
)/ammonia borane
(
NH BH ) solutions. The resulting products prepared in methyl alcohol, ethyl alcohol, and 2-propyl
3
3
Keywords:
In situ synthesized
Spherical nickel–silica composite particles
Hydrolytic dehydrogenation
Ammonia borane
alcohol include spherical particles with the diameters of 600–800, 200–400 nm, and 200–400 nm,
respectively. The evolution of 56, 58, and 62 mL hydrogen was finished in about 50, 90, and
6
respectively. Introducing additional aqueous ammonia borane solution to the solution including the
in situ synthesized particles, the evolution of 58, 50, and 63 mL hydrogen was finished in about
4 3 3
5 min in the presence of the spherical nickel–silica composite particles from aqueous NaBH /NH BH ,
45, 90, and 45 min, respectively, indicating that all the in situ synthesized particles have the recycla-
bility as the catalysts for hydrolysis of NH BH . The in situ synthesized particles prepared in methyl
3
3
alcohol and 2-propyl alcohol show higher rate and amount of hydrogen evolution than in situ synthe-
sized particles prepared in ethyl alcohol.
Ó 2013 Elsevier B.V. All rights reserved.
1
. Introduction
In this study, we investigated the influence of solvents in
morphology of spherical nickel–silica composite particles fol-
Ammonia borane (NH
3 3
BH ) is expected as a hydrogen storage
4 3 3
lowed by in situ activation in aqueous NaBH /NH BH solutions
material for polymer membrane fuel cells for mobile use because
hydrogen with high purity is able to be generated from NH BH
and catalytic activity. In addition, we also investigated the reus-
ability of the in situ synthesized particles for hydrolysis of
3
3
at room temperature. It is reported that nickel-based catalyst is
one of the highly active catalysts for this reaction [1–7]. The results
indicate that dispersion of active metals and/or amorphousness of
active phase play important roles in the catalytic performances for
3 3
NH BH .
2. Experimental
3 3
hydrogen generation from aqueous NH BH solution [1–7]. The
As-prepared spherical nickel–silica composite particles were prepared by the
following sol–gel based techniques. 9.0 mL of an mixed aqueous solution of nick-
morphological effect of nickel–silica composite catalyst was re-
ported by comparing the activity between composite catalyst and
supported catalyst [4]. In recent years, the fabrication and study
of core–shell solid and hollow microspheres with well-defined
structures have attracted substantial interest because of their po-
tential applications in controlled drug delivery system, lightweight
fillers, catalysis, chromatography, vessels for confined reactions,
and photonic band gap material [8–13]. There have been devel-
oped several strategies, such as heterophase polymerization/com-
el nitrate hexahydrate (Ni(NO
nine (Acros, >98%), as a promoter for the reaction to form silica spheres [24], was
added to 180 mL of methyl alcohol (Kanto Chem. Co., >99.5%), ethyl alcohol
3
)
2
ꢀ6H
2
O, Soekawa Chem. Co., >99.0%) and L(+)-argi-
(
Kanto Chem. Co., >99.5%), or 2-propyl alcohol (Kanto Chem. Co., >99.5%), and
then the solution was stirred at 323 K for 17 h after adding 215.2 L of tetraeth-
l
oxysilane (TEOS, Kanto Chem. Co., >99.5%) into the methyl alcohol, ethyl alcohol,
or 2-propyl alcohol solution. The resulting solution was filtered, washed in ethyl
alcohol, and dried in a desiccator.
4
The obtained powder was mixed with 5 mg of NaBH (Kanto Chemical Co.,
>
98.5%), 27.5 mg of NH BH (Aldrich, 90%) in a two-necked round-bottom flask.
3
3
bined with
a sol–gel process [14,15], emulsion/interfacial
One neck was connected to a gas burette, and the other was fitted with a septum
inlet to introduce the distilled water (5 mL). The reaction started when the distilled
water was added to the mixture of the catalyst, NaBH , and NH BH , and the evo-
4 3 3
polymerization approach [16], spray-drying method [17], self
assembly technique [18], surface living polymerization process
[
19], and the template-based route [20–23] to prepare hollow
lution of gas was monitored using the gas burette. The reactions were carried out
at room temperature in air.
spheres comprising polymeric or ceramic materials.
In order to confirm recyclability of in situ synthesized spherical nickel–silica
composite particles, a further aliquot of the aqueous NH
3 3
BH solution (0.16 M,
5
mL) was subsequently added to the reaction flask and the evolution of gas was
⇑
Corresponding author. Tel.: +81 3 3259 0810; fax: +81 3 3293 7572.
E-mail address: umegaki.tetsuo@nihon-u.ac.jp (T. Umegaki).
monitored using the gas burette after the hydrogen generation reaction was
completed.
0
925-8388/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jallcom.2013.02.067

S314
T. Umegaki et al. / Journal of Alloys and Compounds 580 (2013) S313–S316
The morphologies of the catalysts were observed using a Hitachi FE2000 trans-
mission electron microscope (TEM) operating at an acceleration voltage of 200 kV.
Diffuse reflectance ultraviolet and visible (DRUV–Vis) spectra were recorded on a V-
670 (JASCO) UV–Vis–NIR spectrophotometer with barium sulfate as standard spec-
tra over the range of 200–800 nm.
3
. Results and discussion
Fig. 1 shows time course of the hydrogen evolution from aqueous
NaBH /NH BH solutions in the presence of spherical nickel–silica
4 3 3
composite particles prepared in various solvents. The reaction rate
and the amount of hydrogen evolution depend on the catalysts. The
evolution of 56, 58, and 62 mL hydrogen was finished in 50, 90, and
6
5 min the presence of the spherical particles prepared in methyl
alcohol, in ethyl alcohol, and 2-propyl alcohol, respectively. The effect
of NaBH has been reported about nickel based catalyst for hydrolysis
of NH BH [2–4]. In the present reaction system, NaBH
3
with H O, NH BH , and catalyst. Hydrogen is evolved via following
4
3
3
4
was mixed
2
3
two reactions (reactions (2) and (3)) besides reaction (1);
ꢁ
O !4Ni þBOꢁ2 þ8Hþ
4
Ni2þþBH þ2H
2
ð1Þ
ð2Þ
ð3Þ
4
3 3
Fig. 1. Hydrogen generation from hydrolysis of NH BH (0.16 M, 5 mL) with sodium
borohydride in the presence of spherical nickel–silica composite particles prepared
in (a) methyl alcohol, (b) ethyl alcohol, and (c) 2-propyl alcohol at room
NaBH
4
þ2H
2
O !NaþþBO2ꢁþ4H
2
3 3
temperature in air (Ni/NH BH = 0.06).
BH
3
2
O !NHþ4 þBO þ3H
ꢁ
NH
3
þ2H
2
2
Fig. 2. TEM images of spherical nickel–silica composite spheres prepared in (a and b) methyl alcohol, (c and d) ethyl alcohol, and (e and f) 2-propyl alcohol before and after
in situ activation in aqueous NaBH /NH BH solutions.
4
3
3

T. Umegaki et al. / Journal of Alloys and Compounds 580 (2013) S313–S316
S315
Under the present reaction condition, about 12 mL of hydrogen
4 3 3
alcohol followed by in situ activation in aqueous NaBH /NH BH
ꢁ4
(
4.8 ꢂ10 mol) is generated via reaction (2) from residual amount
solutions has few spherical particles with hollow structure as
shown in Fig. 2f. From the figure, the diameter of the spherical
particles was the same as that of the particles of the as-prepared
sample.
Fig. 3 shows the diffuse reflectance of UV–Vis (DRUV–Vis)
absorption spectra of spherical nickel–silica composite particles
ꢁ
4
of NaBH
of NaBH
4
consumed via the reaction (1) (1.3 ꢂ10 (total amount
ꢁ4
4
)ꢁ0.1 ꢂ10 (amount of NaBH
4
consumed via the reac-
ꢁ4
tion (1)) = 1.2 ꢂ10 mol), and about 59 mL of hydrogen
ꢁ4
(
24.0 ꢂ10 mol) is generated via reaction (3), experimentally.
The molar ratio of hydrolytically generated hydrogen to the initial
NH BH in the presence of the spherical particles prepared in
3
3
4 3 3
before and after in situ activation in aqueous NaBH /NH BH
methyl alcohol, ethyl alcohol, and 2-propyl alcohol, are 2.4, 2.6,
and 2.6, respectively. The results indicate that the spherical parti-
cles prepared in methyl alcohol and 2-propyl alcohol followed by
solutions. In all the spectra before the reaction, the observed
absorption bands can be attributed to the electronic transitions
3
3
3
3
assigned as T1g(P)
A2g(F) and T1g(F)
A2g(F) located at
in situ activation in aqueous NaBH
4
/NH
3
BH
3
solutions show higher
2+
3
50–400 nm and at 550–650 nm for Ni , respectively [25], indi-
reaction rate of hydrogen evolution than the spherical particles
prepared in ethyl alcohol followed by in situ activation in aqueous
cating that all the samples before the reaction include octahedral
coordination of Ni(II). Compared with the spectra of all the samples
before the reaction, the intensity of those peaks in the spectra of all
the samples after the reaction decreased. These results and the re-
sults in Fig. 1 indicate that nickel species in all the as-prepared
spherical particles can be sufficiently reduced to show high activity
NaBH
Fig. 2 illustrates TEM images of the spherical nickel–silica com-
posite particles before and after in situ activation in aqueous NaBH
NH BH solutions. The as-prepared samples prepared in methyl
4 3 3
/NH BH solutions.
4
/
3
3
alcohol, ethyl alcohol, and 2-propyl alcohol include spherical parti-
cles with the diameter of ca. 600–800, 200–400, and 200–400 nm as
shown in Fig. 2a, c, and e, respectively. After in situ activation in
for hydrolytic dehydrogenation of NH
BH solution.
Fig. 4 shows hydrogen evolution from aqueous NH
3
BH
3
in aqueous NaBH
4
/NH
3
3
3
BH solution
3
4 3 3
aqueous NaBH /NH BH solutions, the hollow nickel–silica compos-
in the presence of the in situ synthesized spherical nickel–silica
composite particles. All the in situ synthesized spherical particles
ite spheres were obtained. All the catalysts maintain the particle size
same as the as-prepared spherical particles, however, each catalyst
has intrinsic hollow structure. The sample prepared in methyl alco-
show the catalytic activity for the dehydrogenation of NH
3 3
BH
introducing additional aqueous NH BH solution in the suspension
3
3
4 3 3
hol followed by in situ activation in aqueous NaBH /NH BH solu-
of the in situ synthesized spherical particles. The reaction rate and
the amount of hydrogen evolution depend on the catalysts. The
evolution of 58, 50, and 63 mL hydrogen was finished in 45, 90,
and 45 min in the presence of the in situ synthesized spherical par-
ticles prepared in methyl alcohol, ethyl alcohol, and 2-propyl alco-
hol introducing additional aqueous NH BH solution in the
3 3
solution, respectively. The result indicates that all the in situ syn-
thesized spherical particles have the ability for recycle use for
tions has few spherical particles with hollow structure as shown in
Fig. 2b. From the figure, the diameter of the spherical particles was
the same as that of the particles of the as-prepared sample. On the
other hand, from Fig. 2d, the sample prepared in ethyl alcohol
4 3 3
followed by in situ activation in aqueous NaBH /NH BH solutions
has hollow spheres with the wall thickness of ca. 60 nm and the
diameter of the hollow spheres same as that of the particles in the
as-prepared sample, indicating that the hollow nickel–silica
composite spheres was formed during the dehydrogenation in
3 3
hydrolysis of NH BH , and the hydrogen evolution rate and
amount depend on the catalyst. The in situ synthesized spherical
particles obtained from as-prepared samples prepared in methyl
4 3 3
aqueous NaBH /NH BH solution. The sample prepared in 2-propyl
Fig. 3. DRUV–Vis spectra of spherical nickel–silica composite particles prepared in (a) methyl alcohol, (b) ethyl alcohol, and (c) 2-propyl alcohol before and after in situ
activation in aqueous NaBH /NH BH solutions.
4
3
3

S316
T. Umegaki et al. / Journal of Alloys and Compounds 580 (2013) S313–S316
prepared in each solvent are the same as each other. The evolution
of 58, 50, and 63 mL hydrogen was finished in about 45, 90, and
5 min introducing additional aqueous NH BH solution to the
4
3
3
solution in the presence of the in situ synthesized spherical nick-
el–silica composite particles prepared in methyl alcohol, ethyl
alcohol, and 2-propyl alcohol, respectively, indicating all the
in situ synthesized spherical particles have the ability for recycle
3 3
use for hydrolysis of NH BH . The in situ synthesized spherical par-
ticles prepared in methyl alcohol and 2-propyl alcohol show higher
rate and amount of hydrogen evolution than in situ synthesized
spherical particles prepared in ethyl alcohol.
Acknowledgement
Special thanks are given to Dr. H. Ikake for the use of UV–Vis
spectrometer.
References
[
[
1] Q. Xu, M. Chandra, J. Power Sources 163 (2006) 364–370.
2] J.-M. Yan, X.-B. Zhang, S. Han, H. Shioyama, Q. Xu, Inorg. Chem. 48 (15) (2009)
3 3
Fig. 4. Hydrogen generation from the hydrolysis of NH BH in the presence of
in situ synthesized spherical nickel–silica composite particles prepared in (a)
7389–7393.
methyl alcohol, (b) ethyl alcohol, and (c) 2-propyl alcohol. Ni/NH
each cycle) at room temperature in air.
3
BH
3
= 0.06 (at
[3] T. Umegaki, J.-M. Yan, Z.-B. Zhang, H. Shioyama, N. Kuriyama, Q. Xu, Int. J.
Hydrogen Energy 34 (9) (2009) 3816–3822.
[
4] T. Umegaki, J.-M. Yan, X.-B. Zhang, H. Shioyama, N. Kuriyama, Q. Xu, J. Power
Sources 191 (2009) 209–216.
alcohol and 2-propyl alcohol show higher rate and amount of
hydrogen evolution than in situ synthesized spherical particles ob-
tained from as-prepared samples prepared in ethyl alcohol. It has
been reported that the catalytic activity of the hollow nickel–silica
composite spheres depends on the reducibility of active nickel spe-
cies included in the hollow spheres and that the reducibility of the
nickel species depends on the preparation conditions of the hollow
spheres [26]. While the difference of the hydrogen evolution rates
and amounts among the catalysts in this study was not so large, it
might be related with the reducibility of the active nickel species
included in the spherical particles.
[5] Ö. Metin, S. Özkar, S. Sun, Nano Res. 3 (9) (2010) 676–684.
[
[
[
6] Ö. Metin, S. Özkar, Int. J. Hydrogen Energy 36 (2011) 1424–1432.
7] P.Z. Li, K. Aranishi, Q. Xu, Chem. Commun. 48 (26) (2012) 3173–3175.
8] M. Yang, J. Ma, C.L. Zhang, Z.Z. Yang, Y.F. Lu, Angew. Chem. Int. Ed. 44 (2005)
6727–6730.
[
9] D.G. Shchukin, E.A. Ustinovich, G.B.H. Sukhorukov Mohwald, D.V. Sviridov,
Adv. Mater. 17 (2005) 468–472.
[
10] M.M. Ren, R. Ravikrishna, K.T. Valsaraj, Environ. Sci. Technol. 40 (2006) 7029–
7033.
11] P. Jiang, J.F. Bertone, V.L. Colvin, Science 291 (2001) 453–457.
12] Y. Li, J. Shi, Z. Hua, H. Chen, M. Ruan, D. Yan, Nano Lett. 3 (2003) 609–612.
13] U. Jeong, Y.L. Wang, M. Ibisate, Y.N. Xia, Adv. Funct. Mater. 15 (2005) 1907–
1921.
[
[
[
[
[
14] I. Tissot, J.P. Reymond, F. Lefebvre, E. Bourgeat-lami, Chem. Mater. 14 (3)
(
2002) 1325–1331.
15] A. Imhof, Langmuir 17 (12) (2001) 3579–3585.
4
. Conclusion
[16] P.J. Bruinsma, A.Y. Kim, J. Liu, S. Baskaran, Chem. Mater. 9 (11) (1997) 2507–
512.
17] Y. Lu, H. Fan, A. Stump, T.L. Ward, T. Rieker, C.J. Brinker, Nature 398 (1999)
23–226.
[18] B.M. Discher, Y.Y. Won, D.S. Ege, J.C.M. Lee, F.S. Battes, D.E. Discher, Science 284
1999) 1143–1146.
2
[
Spherical nickel–silica composite particles were synthesized by
2
sol–gel based method in various solvent using
promoter for the reaction followed by in situ activation in aqueous
NaBH /NH BH solutions. The resulting powder products prepared
in methyl alcohol, ethyl alcohol, and 2-propyl alcohol include
spherical particles with the diameters of nm, 600–800, 200–
L(+)-arginine as a
(
[
[
19] T. von Werne, T.E. Patten, J. Am. Chem. Soc. 123 (31) (2001) 7497–7505.
20] H. Wang, Y. Song, C.J. Medforth, J.A. Shelnutt, J. Am. Chem. Soc. 128 (29) (2006)
9284–9285.
4
3
3
[
[
21] T. Chen, P.J. Colver, A.F. Bon, Adv. Mater. 19 (17) (2007) 2286–2289.
22] P.M. Arnal, C. Weidenthaler, F. Schüth, Chem. Mater. 18 (11) (2006) 2733–
4
00 nm, and 200–400 nm, respectively. The evolution of 56, 58,
2739.
and 62 mL hydrogen was finished in about 50, 90, and 65 min in
the presence of the spherical nickel–silica composite particles pre-
pared in methyl alcohol, ethyl alcohol, and 2-propyl alcohol from
[23] M. Titirici, M. Antonietti, A. Thomas, Chem. Mater. 18 (16) (2006) 3808–3812.
[
[
24] T. Yokoi, Y. Sakamoto, O. Terasaki, Y. Kubota, T. Okubo, T. Tatsumi, J. Am. Chem.
Soc 128 (42) (2006) 13664–13665.
25] D. Brühwiler, H. Frei, J. Phys. Chem. B 107 (33) (2003) 8547–8556.
aqueous NaBH /NH BH
4 3 3
solution, respectively, indicating that the
[26] T. Umegaki, C. Takei, Y. Watanuki, Q. Xu, Y. Kojima, J. Mol. Catal. A: Chem. 371
(2013) 1–7.
hydrogen evolution rate in the presence of spherical particles