Hydrolytic dehydrogenation of amine-boranes catalyzed by graphene supported rhodium-nickel nanoparticles

Article abstract of DOI:10.1016/j.catcom.2014.09.042

Well dispersed rhodiumnickel (RhNi) nanoparticles (NPs) supported on graphene have been synthesized through an in situ co-reduction procedure under ambient condition, which shows high catalytic activity and durability for hydrolysis of ammonia borane and

Full text of DOI:10.1016/j.catcom.2014.09.042

Catalysis Communications 59 (2015) 14–20
Contents lists available at ScienceDirect
Catalysis Communications
journal homepage: www.elsevier.com/locate/catcom
Short Communication
Hydrolytic dehydrogenation of amine-boranes catalyzed by graphene
supported rhodium–nickel nanoparticles
Junfeng Shen a,1, Nan Cao a,1, Yang Liu , Man He a,1, Kai Hu a,1, Wei Luo a,b,1,⁎, Gongzhen Cheng a,1,
c
⁎
a
College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, Hubei 430072, PR China
Suzhou Institute of Wuhan University, Suzhou, Jiangsu 215123, PR China
School of Science, Wuhan Institute of Technology, Wuhan 430074, PR China
b
c
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 13 August 2014
Received in revised form 22 September 2014
Accepted 23 September 2014
Available online 30 September 2014
Well dispersed rhodium–nickel (RhNi) nanoparticles (NPs) supported on graphene have been synthesized
through an in situ co-reduction procedure under ambient condition, which shows high catalytic activity and
durability for hydrolysis of ammonia borane and methylamine borane.
©
2014 Elsevier B.V. All rights reserved.
Keywords:
Nanoparticles
Rhodium
Nickel
Graphene
Amine-borane
1
. Introduction
The catalytic performance of the metal NPs is highly dependent on
the dispersion of the active metals [6], and one of the most critical prob-
lems is the aggregation of NPs into bulk metal during the catalytic pro-
cess [7]. To solve this problem, appropriate supports have been
designed for restraining the agglomeration of the metal NPs [8]. Up to
now, various types of supported materials have been employed to
3 3
Ammonia borane (H N-BH , AB) complex is considered to be the
most promising candidate for portable hydrogen application among
all other practical hydrogen storage materials due to its high hydrogen
content (19.6% wt), high stability, and environmental benignity [1]. As
the derivative of AB, methylamine borane (CH
has also been studied due to its high gravimetric hydrogen content
11.1 wt.%). The release of hydrogen from AB and MeAB could be ob-
tained via solid phase thermolysis [2], catalytic dehydrogenation in
non-aqueous solvents [3], and hydrolysis [4]. With appropriate catalyst,
hydrolysis of AB or MeAB could release as much as 3 mol of hydrogen
per mol of AB or MeAB, which appears to be the most convenient one
for portable hydrogen storage applications according to Eqs. (1) and
3
NH
2
-BH
3
, MeAB)
uniformly disperse Rh NPs, such as TiO
2
[9a], zeolite framework [9b],
and γ-Al [9c], and their catalytic activity toward hydrolysis of AB
2 3
O
(
has also been studied. Graphene, a single-atom-layer carbon material
holding fascinating properties such as high specific surface area, superi-
or electrical conductivity, high chemical stability, has been widely used
as an ideal substrate for growing and anchoring of metal NPs [10]. How-
ever, the reports about Rh NPs supported on graphene and their catalyt-
ic activity toward hydrolysis of AB, to the best of our knowledge, are
rare.
(
2) [5]. So far, many catalyst systems have been tested for hydrogen
generation from the hydrolysis of AB and MeAB; however, the optimal
compromise between costs, efficiency and recyclability still remains
considerable challenges.
Herein, we report a facile in situ synthesis of graphene supported
RhNi NPs using MeAB as reductant in a one-step co-reduction route at
room temperature under ambient atmosphere. Their catalytic activities
toward hydrolysis of AB and MeAB have also been tested.
catalyst
NH −BH ðaqÞ þ 2 H O ðIÞ
NH BO ðaqÞ þ 3 H ðgÞ
ð1Þ
3
3
2
4
2
2
2. Experimental
catalyst
MeNH −BH ðaqÞ þ 2 H O ðIÞ
ðMeNH ÞBO ðaqÞ þ 3 H ðgÞ ð2Þ
2.1. Chemicals and materials
2
3
2
3
2
2
Ammonia borane (NH
Sinopharm Chemical Reagent Co., Ltd, ≥96%), rhodium (III) chloride
hydrate (RhCl ·nH O, TCI Shanghai Co., Ltd. 98%), nickel chloride
3 3
-BH , AB, Aldrich, 90%), sodium borohydride
⁎
Corresponding authors.
E-mail addresses: wluo@whu.edu.cn (W. Luo), gzcheng@whu.edu.cn (G. Cheng).
Tel.: +86 2768752366.
(
1
3
2
http://dx.doi.org/10.1016/j.catcom.2014.09.042
1566-7367/© 2014 Elsevier B.V. All rights reserved.

J. Shen et al. / Catalysis Communications 59 (2015) 14–20
15
(
a)
(b)
(
c)
(d)
C
O
Ni
Cu
Ni
Si Rh
0
200
400
600
800
1000
binding energy / eV
Fig. 1. (a)–(b). TEM image of the RhNi/graphene with different magnifications. (a inset) Particle size distributions of RhNi/grapheme. (c). TEM image of the RhNi/graphene NPs after the
fifth cycle. (d). EDX of RhNi/graphene.
hexahydrate (NiCl
99%), methylamine hydrochloride (CH
Reagent Co., Ltd, ≥96%), potassium permanganate (KMnO
Chemic Co., Ltd, ≥99.5%), hydrogen peroxide (H , Sinopharm Chem-
ical Reagent Co., Ltd, ≥30%), phosphoric acid (H PO , Sinopharm Chem-
ical Reagent Co., Ltd, AR), sulfuric acid (H SO , Sinopharm Chemical
Reagent Co., Ltd, 95–98%), tetrahydrofuran (C O, Sinopharm Chemi-
10O,
2
·6H
2
O, Sinopharm Chemical Reagent Co., Ltd,
NH HCl, Sinopharm Chemical
, Shanghai
(Sinopharm Chemical Reagent Co., Ltd, ≥99.85%). All chemicals were
used as obtained. We use ordinary distilled water as the reaction
solvent.
≥
3
2
4
2 2
O
3
4
2.2. Graphene oxide (GO) preparation
2
4
4 8
H
GO was made by a modified Hummers method [11]. In an improved
4
cal Reagent Co., Ltd, ≥99%), dimethyl ether anhydrous (C H
synthesis of graphene oxide, a 9:1 mixture of concentrated H
2 4
SO /
Sinopharm Chemical Reagent Co., Ltd, ≥99.7%), and graphite power
H
3
PO (360:40 mL) was added to a mixture of graphite flakes (3.0 g)
4
D
G
RhNi/graphene
RhNi/graphene
GO
GO
1
0
20
30
40
50
60
1000
1200
1400
Raman shift / cm-1
1600
1800
2
Theta / degree
Fig. 2. XRD patterns of GO and RhNi/graphene.
Fig. 3. Raman spectra of GO and RhNi/graphene.

16
J. Shen et al. / Catalysis Communications 59 (2015) 14–20
3
2
2
1
1
0
0
.0
.5
.0
.5
.0
.5
.0
RhNi/graphene
Ni/Rh=2.5
Ni/Rh=5
GO
Ni/Rh=7.5
Ni/Rh=10
Rh(0.002mmol)
Ni(0.03mmol)
4
000
3500
3000
2500
2000
1500
1000
500
0
1
2
3
4
5
6
7
8
9
10 11 12
Wavenumber/cm-1
time(min)
Fig. 4. FTIR spectra of GO and RhNi/grapheme.
Fig. 6. Time plots of catalytic dehydrogenation of AB over the RhNi/graphene catalysts at
ambient condition. Rh/AB = 0.002 (molar ratio).
and KMnO
for 12 h. The reaction was cooled to room temperature and poured onto
ice (~400 mL) with 30% H (3 mL). The addition of 2 mL of excess
was followed until observation of a permanent yellow color,
which indicates the complete oxidation of graphite. The resultant solu-
tion was centrifuged to obtain the product. The product was washed by
deionized water, 30% diluted hydrochloric acid and absolute ethyl alco-
hol for many times and dried under vacuum at 25 °C.
4
(18.0 g). The reaction was then heated to 50 °C and stirred
to get a uniform dispersion. 4 mL solution contained 0.002 mmol
RhCl and 0.015 mmol NiCl was added into the flask. One neck was
3 2
connected to a gas burette, and the other was connected to a pressure-
equalization to introduce AB or MeAB. 4 mL of solution containing
2 2
O
2 2
H O
90 mg MeAB was kept in the pressure-equalization. The reaction started
when the MeAB solution was added to the flask with vigorous stirring.
The evolution of gas was measured by recording the displacement of
water level from the graduated burette. After the hydrogen generation re-
action was completed, 2 mL of solution containing 30.8 mg AB was added
with evolution of gas being monitored. A water bath was used to control
the temperature of the reaction solution. In order optimize the reaction
condition for catalytic dehydrogenation of AB, the molar ratio of Ni/Rh
varied from 0, 2.5, 5, 7.5, and 10, in different reaction trials, when the
molar ratio of Rh to AB was kept as a constant of 0.002.
2
3 2 3
.3. Preparation of methylamine borane (CH NH -BH , MeAB)
MeAB was synthesized by the method reported in the literature [12].
Sodium borohydride (1.8925 g, 0.05 mol) and methylamine hydrochlo-
ride (3.376 g, 0.05 mol) were added to a 250 mL two-neck round-
bottom flask with a neck connected to a condenser. THF (100 mL) was
transferred to the flask, and the contents were vigorously stirred at
2
5 °C. The reaction was carried out at room temperature under nitrogen
atmosphere. After 12 h, the resultant solution was filtered by suction fil-
tration and the filtrate was concentrated under vacuum at room tem-
perature. The product was purified by diethyl ether.
2.5. Kinetic studies of hydrolytic dehydrogenation of AB (MeAB) catalyzed
by Rh Ni7.5/graphene catalysts
1
1
Sets of experiments with different amounts of Rh Ni7.5/graphene
2
.4. In situ synthesis of RhNi/graphene catalysts
catalysts (0.017, 0.0225, 0.034, 0.0425 mmol) were performed at
room temperature (25 ± 0.2 °C), while AB was kept as a constant of
1 mmol to determine the rate law of the catalytic hydrolysis of AB
(MeAB). The temperatures varied from 25 to 40 °C, while the molar
In a typical experiment, 10 mg GO was dissolved in 2 mL of water
kept in a two-necked round-bottom flask. Ultrasonication was required
(
a)
(b)
0
s
0
5
1
s
Rh 3d5/2
Ni 2p3/2
514.8 s
14.8 s
017.5 s
Rh 3d3/2
1017.5 s
Ni 2p1/2
3
20 318 316 314 312 310 308 306 304 302
Binding energy (eV)
885
880
875
870
865
860
855
850
Binding energy (eV)
1
Fig. 5. The XPS spectra of (a) Rh and (b) Ni in Rh Ni7.5/graphene before (0 s) and after (514.8 s and 1017.5 s) argon sputtering.

J. Shen et al. / Catalysis Communications 59 (2015) 14–20
17
Table 1
3
2
2
1
.0
.5
.0
.5
Metal loadings of the RhNi catalysts.
Catalyst
Metal loading (%)
Rh
Rh
Rh
Rh
1
1
1
1
Ni2.5
Ni
Ni7.5
Ni10
5.05
8.20
11.83
13.94
5
ratio of Rh to AB (MeAB) was kept at 0.002 to obtain the constant acti-
vation energy (E ).
1.0
a
0
0
.5
.0
2
.6. Stability test
For stability test, catalytic reactions were repeated 5 times by adding
0
5
10
15
20
time(min)
another equivalent of AB/MeAB (1 mmol) into the mixture after the
previous cycle. The molar ratio of Rh to AB (MeAB) was kept at 0.002.
Fig. 7. Time plots of catalytic dehydrogenation of AB over the Rh
1 1
Ni7.5/graphene, Rh Ni7.5/
γ-Al , Rh Ni7.5/SiO and Rh Ni7.5 NPs under ambient conditions. Rh/AB = 0.002.
O
2 3
1
2
1
2
.7. Characterization
(
Renishaw, RM-1000) at 514.5 nm excitation wavelength. X-ray photo-
TEM images were obtained using a FEI Tecnai G20 U-Twin TEM in-
electron spectroscopy (XPS) measurement was performed with a
Kratos XSAM 800 spectrophotometer. The inductively coupled
plasma-atomic emission spectroscopy (ICP-AES) was performed on
IRIS Intrepid II XSP (Thermo Fisher Scientic, USA).
strument operating at 200 kV. Powder X-ray diffraction (XRD) patterns
were measured by a Bruker D8-Advance X-ray diffractometer using Cu
Ka radiation source (λ = 0.154178 nm) with a velocity of 6° min−1
.
FTIR spectra were collected at room temperature using a Thermo
−
1
FTIR-iS10 instrument with KBr discs in the 400–4000 cm
region.
Raman spectra were carried out with a confocal Raman microscope
3. Results and discussion
Table 2
3.1. Synthesis and characterization
Catalytic activity of catalysts used for the hydrolytic dehydrogenation of AB.
In a typical synthesis, the graphene supported RhNi NPs were pre-
Catalyst
TOF
mol H
M = Ru, Rh, Ag
Ea
Ref.
mol− M min−1
1
)
(kJ mol−1)
pared by adding MeAB into the precursor solution containing RhCl
(
2
3
,
NiCl , and graphene oxide (GO) at room temperature. The microstruc-
2
Ru/C
RhNi/graphene
Ru(0)@MWCNT
Rh@TiO
Water soluble
laurate-stabilized
rhodium(0) nanoclusters
PSSA-co-MA stabilized Ru
nanoclusters
429.5
420
329
260
200
34.8
38.2
33
65.5
43.6
[16]
This study
[17]
[9a]
[18]
ture of RhNi/graphene NPs was characterized by transmission electron
microscopy (TEM) and energy dispersive X-ray spectrometry (EDX).
As shown in Fig. 1a–b, the NPs were well dispersed on graphene,
which helps to prevent the agglomeration. The EDX spectrum in
Fig. 1d confirms the coexistence of Rh and Ni. Fig. 2 shows the power
XRD pattern of the as-prepared RhNi/graphene NPs, in which the dif-
fraction peak attributed to Rh(111) is observed. Furthermore, the
most intense peak at around 8.4° corresponds to the GO disappeared,
and new peak at around 23.2° is observed in the as-prepared graphene
supported NPs, indicating that the GO is successfully reduced to
graphene. In the Raman spectroscopy (Fig. 3), the GO and graphene
2
187.6
54
[19]
Rh/γ-Al
2
O
3
178
178
102.4
100
99.3
90
21
[9c]
[20]
[21]
[22]
[4b]
[9b]
2.80 wt.% Ru@MIL-101
51.1
20.0
11.7
36.2
66.9
Ag@Co/graphene
Ru/graphene
Ag@CoNi/graphene
Zeolite framework
stabilized
−1
supported NPs exhibit two peaks centered at 1354 and 1596 cm , cor-
responding to the D and G bands of the carbon products, respectively.
The intensity ratio of the D to G band (I
reflect the degree of graphitization of carbonaceous materials and defect
density. After loading of the RhNi NPs, the I /I of GO is increased from
.28 to 1.91. The relative changes in the D to G peak intensity ratio con-
D G
/I ) is generally accepted to
rhodium(0) nanoclusters
Ru@Al
treatment
Ag@CoFe/graphene
Ru/γ-Al
Ag@Ni/graphene
Laurate-stabilized
ruthenium(0)
2
O
3
after acetic acid
83.3
46
[23]
D
G
82.9
77
77.0
75
32.8
23
49.6
47
[24]
[9c]
[21]
[25]
1
2 3
O
firm the reduction of GO during the in situ fabrication. Fig. 4 shows the
FTIR spectra of GO and graphene supported RhNi NPs. It can be seen
−
1
clearly that the disappearance of C_O peak at 1634 cm , C\OH
nanoclusters
−1
−1
peak at 1227 cm and the C\O peak at 1057 cm of GO after the for-
mation of graphene supported RhNi NPs, further indicating the GO was
reduced to graphene during the process. The X-ray photoelectron spec-
Ag@NiFe/graphene
Ru@Co/graphene
Ru@Ni/graphene
Ru@Al
Ni@Ru
Ru@Ni/C black
Ru@Co/C black
Ru/γ-Al
Ag0.5@Co0.5/graphene
RuCo (1:1)/γ-Al
RuCu/graphene
RuCu (1:1)/γ-Al O
2 3
50.2
40.5
39.9
39.6
30.6
29.4
29.1
23.1
21
–
[24]
[26]
[27]
[23]
[28]
[29]
[29]
[30]
[31]
[32]
[33]
[32]
–
36.6
48
44
37.9
21.2
67
39.3
47
2
O
3
1
troscopy (XPS) of Rh NI7.5/graphene (Fig. 5) showed characteristic sig-
nals for Rh and Ni, indicating the co-existence of both metals. After Ar
sputtering, the Ni 2p3/2 and Ni 2p1/2 peaks were observed with binding
energies of 852.7 and 870.2 eV, and the Rh 3d5/2 and Rh 3d3/2 peak
2 3
O
0
0
(312.0 and 307.2 eV, respectively), which correspond to Ni and Rh .
The formation of oxidized Ni and Rh before Ar sputtering shows that
the sample most likely occurs during the sample preparation process
for the XPS measurements [13].
2
O
3
16.5
15.9
8.2
30.4
52

18
J. Shen et al. / Catalysis Communications 59 (2015) 14–20
(
a)
(b)
3
3
3
3
.8
.6
.4
.2
3
.0
.5
.0
.5
.0
.5
.0
2
2
1
1
0
0
ln rate=1.03 ln[Cat]+6.96
Ni+Rh=0.017 mmol
Ni+Rh=0.0255 mmol
Ni+Rh=0.034 mmol
Ni+Rh=0.0425 mmol
3.0
.8
2
2.6
-4.2
0
1
2
3
4
5
-4.0
-3.8
-3.6
lnc
-3.4
-3.2
-3.0
time(min)
2 1 1
Fig. 8. (a). mol H /mol AB versus time graph for the Rh Ni7.5/graphene catalytic hydrolysis of AB for different Rh Ni7.5/graphene concentrations at 25 ± 0.2 °C; (b). The plot of hydrogen
1
generation rate versus the concentration of Rh Ni7.5/graphene NPs (both in logarithmic scale).
3
NPs
.2. Catalytic activities for hydrolysis of AB and MeAB by Rh
1
Ni7.5/graphene
noble metal (Table 2). Additionally, to study the effects of the supported
materials on the catalytic performances of the as-synthesized RhNi cat-
1 2 1 2 3 1
alysts, Rh Ni7.5/SiO , Rh Ni7.5/γ-Al O , and Rh Ni7.5 are prepared and
When the GO solution containing NiCl
2
is mixed with MeAB, the
their catalytic activities toward hydrolysis of AB have been studied. As
shown in Fig. 7, their catalytic activities are both inferior to that of
Rh Ni7.5/graphene, highlighting the dominant factor of graphene in
1
facilitating hydrolysis of AB in our system and the cooperative effect
between graphene and RhNi nanoparticles.
color of the mixture has no changes even after several hours, indicating
the Ni2+ cannot be reduced by MeAB; thus, the pure Ni has no activity
toward catalytic hydrolysis of AB as shown in Fig. 6, which is similar
with Xu's work [14]. When pure Rh NPs were supported on graphene,
keeping the molar ratio of Rh/AB as 0.002, H
2
is completely released
Figs. 8 and 9 show the plots of hydrogen generation from the hydro-
for more than 10 min. Unexpectedly, when Ni was introduced to form
the RhNi NPs, and still keeping the molar ratio of Rh/AB as 0.002, the re-
action time was decreased. When the Ni/Rh molar ratio is 7.5, the re-
1
lysis of AB and MeAB solution in the presence of different Rh Ni7.5/
graphene NPs concentrations at 25 ± 0.2 °C. The initial rate of hydrogen
generation was determined from the initial nearly linear portion of each
plot. The line slopes of the plot of hydrogen evolution rate versus cata-
lyst concentration in a log-log scale are 1.03 and 0.95 respectively, indi-
lease of H
2
can be completed in about 2.5 min, indicating the
synergistic effect of the RhNi nanostructures to the catalytic hydrolysis
of AB. Further increase in the Ni/Rh molar ratio to 10 results in no signif-
icant decrease of the reaction time, indicating that the best Ni/Rh molar
ratio in the RhNi NPs is 7.5. The metal loadings of the catalysts were
determined by ICP-AES as shown in Table 1. The activity in terms of
cating that the hydrolysis of AB and MeAB catalyzed by Rh
graphene NPs is first order with respect to the catalyst concentration.
In order to get the activation energy (E ) of the AB and MeAB
hydrolysis catalyzed by Rh Ni7.5/graphene NPs, the hydrolytic reactions
1
Ni7.5/
a
1
−
1
−1
turnover frequency (TOF) is 420 (mol H
2
min (mol Rh) ) for this
at different temperature range of 25–40 °C were carried out. The values
of rate constant k at different temperatures were calculated from
the slope of the linear part of each plot from Figs. 10a and 11a. The
Arrhenius plot of lnk vs. 1/T for the catalyst is plotted in Figs. 10b and
11b, from which the apparent activation energy was determined to be
as-synthesized NPs; moreover, to the best of our knowledge, this is
the highest value ever reported for the catalytic hydrolysis of AB
among the Rh-based catalyst, and higher than most of other reported
noble metal-based catalysts, if the TOF is normalized in terms of mol
(
a)
(b)3
.8
.6
.4
.2
.0
.8
3
.0
.5
.0
.5
.0
.5
.0
3
3
3
3
2
ln rate=0.95 ln[Cat]+6.67
2
2
1
1
0
0
Ni+Rh=0.017 mmol
Ni+Rh=0.0255 mmol
Ni+Rh=0.034 mmol
Ni+Rh=0.0425 mmol
0
1
2
3
4
5
-4.2
-4.0
-3.8
-3.6
lnc
-3.4
-3.2
-3.0
time(min)
2 1 1
Fig. 9. (a). mol H /mol MeAB versus time graph for the Rh Ni7.5/graphene catalytic hydrolysis of MeAB for different Rh Ni7.5/graphene concentrations at 25 ± 0.2 °C; (b). The plot of
1
hydrogen generation rate versus the concentration of Rh Ni7.5/graphene NPs (both in logarithmic scale).

J. Shen et al. / Catalysis Communications 59 (2015) 14–20
19
(
a)
3
(b)
.0
.5
.0
.5
.0
.5
.0
lnk=-4595.6(1/T)+26.69
Activation Energy
1
1
2.0
1.8
2
2
1
1
0
0
-1
o
Ea=38.21 kJ mol
T=25 C
o
T=30 C
o
11.6
T=35 C
o
T=40 C
1
1.4
11.2
0
1
2
3
4
5
0.00320
0.00325
0.00330
0.00335
time(min)
1/T
2 1
Fig. 10. (a). mol H /mol AB versus time graph for the Rh Ni7.5/graphene catalytic hydrolysis of AB at different temperatures, Rh/AB = 0.002; (b). The Arrhenius plot (ln k versus the
−
1
reciprocal absolute temperature, 1/T (K )).
approximately 38.21 kJ mol− and 31.26 kJ mol−1 respectively, being
1
4. Conclusion
lower than most of the reported Ea values (Table 2), indicating the
superior catalytic performance of the as-synthesized Rh
NPs.
1
Ni7.5/graphene
In summary, for the first time, the RhNi NPs were synthesized by
a one-step in situ method using graphene as the support. The as-
synthesized NPs exhibit superior catalytic activities than their monome-
tallic Rh, Ni NPs, and graphene-free RhNi counterparts. In addition, the
as-synthesized NPs show excellent catalytic activity and good durable
stability for the hydrolytic dehydrogenation of AB and MeAB. Moreover,
this simple synthetic method can be easily extended to facile prepara-
tion other graphene supported metal NPs.
3
.3. Reusability ability
The reusability of the catalyst is crucial in the practical application. The
reusability of Rh Ni7.5/graphene NPs up to the fifth run for hydrolysis of
1
AB and MeAB is shown in Fig. 12. The as-prepared catalysts retain 68%
of their initial catalytic activities in the hydrolysis of AB in the fifth run.
Acknowledgments
In Fig. 12, with our as-synthesized NPs, MeAB can release 3 equiv. H
2
in
less than 2 min at room temperature in the first run under ambient con-
dition, with the TOF measured to be 461 (mol H min (mol Rh) ), and
2
This work was financially supported by the National Natural Science
Foundation of China(21201134), the Natural Science Foundation of
Jiangsu Province(BK20130370), the Natural Science Foundation of
Hubei Province(2013CFB288) and Large-scale Instrument and Equip-
ment Sharing Foundation of Wuhan University.
−
1
−1
retain 77% of their initial catalytic activities after the fifth run. Fig. 1c
shows the representative TEM images of the as-synthesized NPs after
the fifth run durability test. As clearly seen from the TEM image, there is
no obvious aggregation of the RhNi NPs on graphene, indicating that the
graphene can stabilize the as-prepared RhNi NPs at least for five cycles.
Therefore, the decrease in the catalytic activity may be due to the increase
viscosity of the solution or deactivation effect of the increasing
metaborate concentration during the hydrolysis of AB and MeAB [15].
References
[
1] (a) A.D. Sutton, A.K. Burrell, D.A. Dixon, E.B. Garner III, J.C. Gordon, T. Nakagawa,
K.C. Ott, J.P. Robinson, M. Vasiliu, Science 331 (2011) 1426;
(
a)
(b)
1
1
1
1
1
2.0
1.9
1.8
1.7
1.6
lnk=-3760.6(1/T)+23.99
3
.0
.5
.0
.5
.0
.5
.0
2
2
1
1
0
0
Activation Energy
-
1
Ea=31.26 kJ mol
o
T=25 C
o
T=30 C
o
T=35 C
o
11.5
1.4
11.3
T=40 C
1
0
1
2
3
4
5
0.00320
0.00325
0.00330
0.00335
time(min)
1/T
Fig. 11. (a). mol H
reciprocal absolute temperature, 1/T (K )).
2 1
/mol MeAB versus time graph for the Rh Ni7.5/graphene catalytic hydrolysis of MeAB at different temperatures, Rh/AB = 0.002; (b). The Arrhenius plot (ln k versus the
−
1

20
J. Shen et al. / Catalysis Communications 59 (2015) 14–20
(
a)
(b)
3
.0
.5
.0
.5
.0
.5
.0
3.0
1
st
1
2
3
4
st
2
nd
nd
rd
th
2
2
1
1
0
0
3rd
2.5
2.0
1.5
1.0
0.5
0.0
4
5
th
th
5th
1
00
100
8
6
0
0
8
6
4
2
0
0
0
0
0
40
2
0
0
1
2
3
4
5
1
2
3
4
5
Run
Run
0
1
2
3
4
5
6
7
8
0
1
2
3
4
5
6
7
time(min)
time(min)
Fig. 12. (a). Time plots of catalytic dehydrogenation of AB over the Rh
activity of Rh Ni7.5/graphene in successive runs after the reuse for the hydrolysis of AB. (b). Time plots of catalytic dehydrogenation of MeAB over the Rh
to 5th cycles at 25 ± 0.2 °C. Rh/MeAB = 0.002; (b inset). Percentage of initial catalytic activity of Rh Ni7.5/graphene in successive runs after the reuse for the hydrolysis of MeAB.
1
Ni7.5/graphene catalysts from 1st to 5th cycles at 25 ± 0.2 °C. Rh/AB = 0.002; (a inset). Percentage of initial catalytic
1
1
Ni7.5/graphene catalysts from 1st
1
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