A cost effective cobalt nickel nanoparticles catalyst with exceptional performance for hydrolysis of ammonia-borane

Article abstract of DOI:10.1166/jnn.2017.14331

Herein, we successfully report the development a new cost effective CoNi nanoparticles catalyst for the hydrolysis of ammonia borane. The prepared nanocatalysts have been characterized by ICP–AES, XPS, TEM and HR-TEM. The results show that the CoNi nanoparticles with the size of 4.6 nm are successfully supported vulcanxc-72 surface by a simple co-reduced route. The synthesized CoNi nanocatalysts possess an exceptional catalytic performance for hydrolysis of ammonia-borane corresponding to TOF value of 49 mol_H2 mol_cat^-1 min^?1 at 323 K. The excellent catalytic property is attributed not only the formation of ultrafine nanoparticles on vulcanxc-72 surface but also synergistic effect between Co and Ni. More importantly, the catalytic property for hydrolysis of ammonia borane do not obviously decline up to 6 recycles, which shows the exceptional reusability of CoNi NPs/vulcanxc-72.

Full text of DOI:10.1166/jnn.2017.14331

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Nanoscience and Nanotechnology
Vol. 17, 9333–9338, 2017
Copyright © 2017 American Scientific Publishers
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A Cost Effective Cobalt Nickel Nanoparticles
Catalyst with Exceptional Performance for
Hydrolysis of Ammonia-Borane
1
2
1
1ꢀ∗
Qingtao Wang , Feifei Zhang , Fanglin Du , and Tong Liu
1
College of Materials Science and Engineering, Qingdao University of Science and Technology, Qingdao 266000, China
2
Tsinghua Innovation Center in Dongguan, Dongguan 523000, China
Herein, we successfully report the development a new cost effective CoNi nanoparticles catalyst for
the hydrolysis of ammonia borane. The prepared nanocatalysts have been characterized by ICP–
AES, XPS, TEM and HR-TEM. The results show that the CoNi nanoparticles with the size of 4.6 nm
are successfully supported vulcanxc-72 surface by a simple co-reduced route. The synthesized
CoNi nanocatalysts possess an exceptional catalytic performance for hydrolysis of ammonia-borane
−
1
−1
corresponding to TOF value of 49 molH2 mol min at 323 K. The excellent catalytic property is
cat
attributed not only the formation of ultrafine nanoparticles on vulcanxc-72 surface but also syner-
gistic effect between Co and Ni. More importantly, the catalytic property for hydrolysis of ammonia
borane do not obviously decline up to 6 recycles, which shows the exceptional reusability of CoNi
IP: 185.251.14.183 On: Wed, 01 Aug 2018 08:16:08
Copyright: American Scientific Publishers
NPs/vulcanxc-72.
Keywords: Heterogeneous Catal yDs ei sl ,i v eCr eo Nd ib yN Ian ng o ep na trat icles, Hydrosis, Synergistic Effect,
Ammonia Borane.
The ever-growing concerns on energy crisis and environ-
mental pollution have stimulated intensive interest for the
renewable energy and storage materials. Hydrogen (H2ꢁ
with a high energy density and lightweight has been con-
sidered an ideal secondary fuel and energy carrier; there-
fore which could be used in proton exchange membrane
Recently, Co-based bimetallic non-noble nanoparti-
cles (NPs) have exhibited excellent catalytic performance
in hydrolysis of AB due to the synergistic interactions
1
ꢀ2
1
6–18
between two different metals.
To further increase cat-
alytic performance in the hydrolysis reaction, metal cata-
lysts are required to possess smaller particle size, leading
1
9–24
(
PEM) fuel cells to produce electrical power for vehi-
the more active surface sites.
However, most of these
3
–6
cles and electronic devices. Among numerous hydro-
gen storage materials, ammonia borane (NH BH , AB) has
catalysts in nanometer size are easily aggregated to large
particles during the hydrolytic reaction, which results in
the heavy loss of catalytic active sites and serious cat-
3
3
become an attractive candidate for on-board application
because it possesses high gravimetric hydrogen capacity
2
5–27
alytic degradation.
Hence, it is thus crucial to develop
−
1
(
19.6 wt%), low molecular weight (30.86 g mol ꢁ and
protection strategies to stabilize the metal NPs against
agglomeration during the catalytic reaction. Recently, Lu
7
–12
environmentally friendly nature.
With an appropriate
metal-catalyzed hydrolysis, 3 equiv. of hydrogen per mol
of AB could be released from the aqueous solution of
AB. Although there are many reports on hydrolysis of
AB, most of them are focused on noble transition metal
catalysts such as Pt, Ru and Pd, which limited the
practical application due to high material cost. Therefore,
transition metal catalysts such as Ni, Fe and Co have been
explored; however, they have only moderate activity.
group immobilized bimetallic Cu–Co NPs on SiO , and the
2
core–shell nanospheres exhibit excellent hydrolytic prop-
−1 28
erty with activation energy of 24 kJ mol . In addition,
the prepared catalysts possess a good recycling stability in
hydrolysis reaction. Inspired by these results, we success-
fully synthesized CoNi NPs supported vulcanxc-72 car-
bon (XC-72) by a co-reduced route. The CoNi NPs of
about 4.6 nm are supported on XC-72 surfaces. The syn-
thesized CoNi/XC-72 catalysts show high TOF value of
1
3
14
15
∗
−1
−1
Author to whom correspondence should be addressed.
49 molH2 mol min at 323 K for AB hydrolysis.
cat
J. Nanosci. Nanotechnol. 2017, Vol. 17, No. 12
1533-4880/2017/17/9333/006
doi:10.1166/jnn.2017.14331
9333

A Cost Effective Cobalt Nickel NPs Catalyst with Exceptional Performance for Hydrolysis of Ammonia-Borane
Wang et al.
Table I. Catalytic activities of different catalysts for the hydrolysis of
ammonia borane.
In a typical experiment, 60 mg XC-72 was dis-
solved in 3 mL water in a two-neck round-bottom flask
(
30 mL). Ultrasonication was required to get a uniform
Temp. TOF (mol
Ea
(kJ mol
H2
−1
−1
−1
dispersion for 30 min. Then, 100 ꢂL nickel chloride
solution (0.04 mmol/mL) and 100 ꢂL cobalt chloride
(
resulted mixture was stirred for 20 min with a rotating
shaker (220 rpm). A 0.5 mL aqueous solution of sodium
borohydride (NaBH ꢁ (1.3 mol L ꢁ was quickly added
into the resulted mixture under vigorous stirring for 3 min
at 298 K. When the situ synthesis reaction was completed,
0
injected into the mixture using a syringe, a gas burette
filled with water was connected to the reaction flask to
measure the volume of released gas, which could avoid
oxidation of Ni and Co.
Catalyst
(K)
molcat min
ꢁ
ꢁ
Ref.
CoNi/XC-72
Cu@Co/Co
NiCu@C nanofiber
Co/PEI-GO
Cu@FeNi
323
303
298
298
303
298
298
298
298
298
298
298
298
49
8ꢄ36
3ꢄ6
28ꢄ9
51ꢄ3
285ꢄ9
28ꢄ2
This work
0.06 mmol/mL) was added into the XC-72 solution. The
29
30
28
31
24
30
33
34
35
36
37
38
39ꢄ9
4ꢄ69
36ꢄ05
10ꢄ23
40ꢄ9
40ꢄ46
10ꢄ5
28ꢄ4
1ꢄ7
−1
32ꢄ9
4
AuCo/CNT
38ꢄ82
20ꢄ03
–
Ag@Co/graphene
Pd@Co/graphene
Ru@Co/graphene
Cu@FeCo
Au-Co@CN
Ti-supported Co film
Co nanocluser
.5 mL of aqueous solution containing 1 mmol AB was
–
38ꢄ75
–
28
–
35ꢄ5
Transmission electron microscopy (TEM) images were
obtained using Tecnai G2 F30. X-ray photoelectron
spectroscopy (XPS) measurement was performed with
ESCALAB 250Xi spectrophotometer. The metal contents
of the catalyst were analyzed using inductively cou-
pled plasma atomic emission spectroscopy (ICP–AES) on
Leeman PROFILE SPEC.
ratio of catalyst/AB = 0.01. From Figure 1, we could find
that the Co/Ni molar ratio plays an important role for deter-
mining the catalytic activity and selectivity for hydrogen
generation. For monometallic nickel catalysts, almost no
Ammonia borane (NH · BH , Aladdin reagent Co.,
3
3
Ltd, >97%), nickel(II) chloride hexahydrate (NiCl ·
2
6
H O, Sinopharm Chemical Reagent Co., Ltd., >98%),
2
cobalt(II) chloride hexahydrate (CoCl ·6H O, Sinopharm
2
2
Chemical Reagent Co., Ltd., 9 I9P%: )1, 8s 5o .d2 i 5u 1m .1 b4 o. 1r o8 h3y dO r ind :eWed, 01 Aug 2018 08:16:08
Copyright: American Scientific Publishers
(
NaBH , Sinopharm Chemical Reagent Co., Ltd., >96%),
4
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vulcanxc-72 carbon (Cabot corporation, ≥97%). De-
ionized water with the specific resistance of 18.2 Mꢃ·cm
was obtained by reversed osmosis followed by ion-
exchange and filtration.
Figure 1 shows the catalytic properties of Co Ni /XC-
x
1−x
7
2 (0 ≤ x ≤ 1) for hydrolytic reaction with a constant molar
Figure 1. Plots of time versus volume of generated H from AB aque-
Figure 2. Plots of time versus volume of generated H from AB aque-
2
2
ous solution with different Co/Ni molar ratios at 323 K. The molar ratio
ous solution over Co0ꢄ6Ni0ꢄ4/XC-72 at different temperatures (a); arrhenius
of metal/AB = 0.01.
plot (ln(TOF) vs. 1/T) (b). The molar ratio of metal/AB = 0.01.
9334
J. Nanosci. Nanotechnol. 17, 9333–9338, 2017

Wang et al.
A Cost Effective Cobalt Nickel NPs Catalyst with Exceptional Performance for Hydrolysis of Ammonia-Borane
AB. For CoNi/XC-72 catalysts with different molar ratios
of Co/Ni, Co Ni /XC-72 shows the excellent catalytic
0
ꢄ6
0ꢄ4
activity and the corresponding TOF value could achieve
− −1
9.1 molH2 mol min at 323 K, which is higher than
cat
1
4
most of the reported values in Table I. Figure 2 shows the
reactions of AB hydrolysis catalyzed by the Co Ni /XC-
0
ꢄ6
0ꢄ4
7
2 NPs at different temperatures (298–323 K), which could
benefit to obtain the activation energy (E ꢁ. It is seen that
a
the hydrolytic performance will increase with the reaction
temperature increasing. The catalytic reactions are com-
pleted in 14.9, 12.3, 9.1, and 6.5 min at 298, 303, 313, and
3
2
23 K, respectively, which correspond to TOF values of
−1
−1
0.1, 23.9, 33.3, and 49.1 molH2 mol min . The Arrhe-
cat
nius plot of ln TOF versus 1/T for this catalyst is plotted
in Figure 2(b), from which E was calculated as 28.9 kJ ·
a
−1
mol . This value is also lower than most of those reported
results (shown in Table I), which benefits to practical appli-
cation in future. Compared to the other results, the excellent
catalytic property of CoNi/XC-72 is mainly attributed that
XC-72, as an excellent support, benefit to the formation of
the ultrafine CoNi NPs. In order to confirm the effect of
XC-72 on hydrolysis of AB, the CoNi NPs has been pre-
pared and the corresponding catalytic property drastically
decreases (seen in Fig. 3).
Figure 3. Plots of time versus volume of generated H from AB aque-
ous solution over Co0ꢄ6Ni0ꢄ4/XC-72 and Co0ꢄ6Ni0ꢄ4 at 323 K. The molar
ratio of metal/AB = 0.01.
2
H generated from AB aqueous solution, while the addi-
2
tion of cobalt could improve catalytic performance and H2
selectivity activity, which is mainly attributed to the syner-
getic effect between Co and Ni. The synergetic effect may
be mainly ascribed to electronic effects, which also ben-
efits to improve catalytic property for dehydrogenation of
To further investigate the morphologies of CoNi NPs,
transmission electron microscopy (TEM) and high-angle
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Figure 4. TEM and HAADF images of XC-72 (a, b) and Co0ꢄ6Ni0ꢄ4/XC-72 (c, d).
J. Nanosci. Nanotechnol. 17, 9333–9338, 2017
9335

A Cost Effective Cobalt Nickel NPs Catalyst with Exceptional Performance for Hydrolysis of Ammonia-Borane
Wang et al.
Figure 5. XPS spectra of C 1 s, Ni 2p and Co 2p for CoNi/XC-72 after (60 min) Ar etching.
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annular dark-field scanning TEM (HAADF-STEM) are
used. From Figures 4(a) and (b), it is seen that the pure
support material XC-72 possesses the flaky grain with
size of 100 nm. After immobilized CoNi NPs, it is inter-
esting that the discrete CoNi NPs are homogeneously
dispersed on XC-72 surface with an average size of 4.6 nm
the durability of the CoNi/XC-72 nanocatalyst was char-
acterized by adding additional aliquots (1.0 mmol, 200
ꢂL) of AB to the catalyst after the reaction completion
for the last run (Fig. 6). From these results, we can find
that the catalytic activity of the as-prepared CoNi/XC-72
(
Figs. 4(c and d)). The formation of CoNi has also been
confirmed by XPS results. Seen from Figure 5, the peak
at 284.5 eV is attributed to the binding energy of C 1 s. In
addition, there are two peaks located at 853 and 861 eV
0
0
assigned to elemental Ni 2p and Ni 2p1/2, respectively,
3
/2
while the peaks observed at 856 and 873 eV most likely
occurred during the sample preparation process for XPS
0
measurements. The 2p peaks of Co could appear at 781
and 797 eV. The co-existence of Co and Ni peaks confirm
the formation of CoNi alloy and no any possible segrega-
tion of Co NPs and Ni Ps. Furthermore, the inductively
coupled plasma mass spectrometry (ICP-MS) results of the
responding sample show that the relative compositions of
the CoNi NPs yield the following compositions: 58 at%
Co, and 41 at% Ni, in the CoNi/XC-72. From the above
results, it is found that the ultrafine Co Ni NPs have
0
ꢄ6
0ꢄ4
been successfully immobilized on XC-72 surface, which
is response for the excellent catalytic property for the AB
hydrolysis catalyzed by Co Ni /XC-72 NPs.
For the practical application of catalysts, the dura-
bility/stability of catalysts is the key point. Therefore,
Figure 6. Durability test for the generation of H2 from aqueous AB
solution over as-synthesized Co0ꢄ6Ni0ꢄ4/XC-72 catalyst after addition of
the same amounts of AB (1 mmol) at 323 K. The molar ratio of
metal/AB = 0.01.
0
ꢄ6
0ꢄ4
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J. Nanosci. Nanotechnol. 17, 9333–9338, 2017

Wang et al.
A Cost Effective Cobalt Nickel NPs Catalyst with Exceptional Performance for Hydrolysis of Ammonia-Borane
Figure 7. TEM image of Co0ꢄ6Ni0ꢄ4/XC-72 after catalysis.
nanocatalyst has no obvious decrease after a six-time recy-
cle test, indicating the as-prepared CoNi/XC-72 possess
high durability in AB hydrolysis. The stable durability
of CoNi/XC-72 is mainly attributed to avoid aggregation
of CoNi NPs, which is suggested by TEM measurement.
From Figures 7 and 8, no obvious changes in morpholo-
gies and structures are observed, further confirming the
advantage of the confinement effect of XC-72. It should be
noted that magnetic stirring has no negative effect on the
catalytic performance of the magnetic element-containing
NiCo towards dehydrogenation of AB (Fig. 9).
Figure 9. Plots of time versus volume of generated H from AB aque-
ous solution over Co0ꢄ6Ni0ꢄ4/XC-72 by magnetic stirring and shaking at
323 K. The molar ratio of metal/AB = 0.01.
2
show that the optimal molar ratio of Co/Ni is 3/2. Further-
more, the synthesized nanocatalysts show stable durabil-
ity of AB hydrolytic property. The present work provides
an effective strategy to immobilize ultrafine cost effective
metal NPs on XC-72 as the catalysts of AB hydrolysis,
which may be beneficial for the application of AB as a
hopeful chemical hydrogen storage material.
IP: 185.251.14.183 On: Wed, 01 Aug 2018 08:16:08
In summary, the cost effective Co Ni NPs have been
0
ꢄ6
0ꢄ4
Copyright: American Scientific Publishers
successfully supported on XC-72 by a co-reduced route.
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Acknowledgments: This work was supported by the
National Natural Science Foundation of China (Grant
Nos. 51272115 and 21276130).
By using the confinement effect of support, the CoNi NPs
with a diameter of 4.6 nm on XC-72 are achieved. The
formation of CoNi NPs benefits to improve the catalytic
performance for AB hydrolysis, which is corresponding
−
1
−1
the excellent TOF value of 49 mol mol min and acti-
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Received: 23 December 2016. Accepted: 26 January 2017.
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