Co0.85Se bundle-like nanostructure catalysts for hydrogenation of 4-nitrophenol to 4-aminophenol

Article abstract of DOI:10.1039/c4nj01358a

This study demonstrated the preparation of Co_0.85Se bundle-like nanostructures (BNs) by a template-directed approach under solvothermal conditions. The Co_0.85Se BNs were utilized as catalysts in the reduction of 4-nitrophenol in the presence of NaBH₄. The kinetics of the reduction of 4-nitrophenol at three different reaction temperatures were investigated to evaluate the catalytic activity of the Co_0.85Se BNs. The activation energy (E_a), activation enthalpy (ΔH^?), and activation entropy (ΔS^?) of the Co_0.85Se BNs and Co_0.85Se nanoparticles (NPs) are 14.66 kJ mol^-1, 12.15 kJ mol^-1, 42.51 J mol^-1 K^-1, and 17.78 kJ mol^-1, 16.55 kJ mol^-1, 50.66 J mol^-1 K^-1, respectively. The above results revealed that the Co_0.85Se BNs exhibited a higher catalytic performance for the hydrogenation of 4-nitrophenol by NaBH₄ than that of the Co_0.85Se NPs at room temperature. It is believed that the prepared Co_0.85Se BNs have potential applications in catalysis.

Full text of DOI:10.1039/c4nj01358a

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Co Se bundle-like nanostructure catalysts for
0.85
hydrogenation of 4-nitrophenol to 4-aminophenol†
Cite this: New J. Chem., 2014,
3
8, 6147
a
a
a
a
Zai-Xian Zhang,‡ Xian-Wen Wang,‡ Kong-Lin Wu,* Yao-Xiang Yue,
a
a
a
a
ab
Meng-Li Zhao, Juan Cheng, Jiang Ming, Chang-Jiang Yu and Xian-Wen Wei*
This study demonstrated the preparation of Co0.85Se bundle-like nanostructures (BNs) by a template-
directed approach under solvothermal conditions. The Co0.85Se BNs were utilized as catalysts in the
reduction of 4-nitrophenol in the presence of NaBH
4
. The kinetics of the reduction of 4-nitrophenol at
three different reaction temperatures were investigated to evaluate the catalytic activity of the Co0.85Se
‡
‡
BNs. The activation energy (E
a
), activation enthalpy (DH ), and activation entropy (DS ) of the Co0.85Se
Received (in Montpellier, France)
2th August 2014,
À1
À1
À1
À1
1
BNs and Co0.85Se nanoparticles (NPs) are 14.66 kJ mol , 12.15 kJ mol , 42.51 J mol
K
, and
, respectively. The above results revealed that the
Co0.85Se BNs exhibited a higher catalytic performance for the hydrogenation of 4-nitrophenol by NaBH
À1
À1
À1 À1
Accepted 25th September 2014
1
7.78 kJ mol , 16.55 kJ mol , 50.66 J mol
K
DOI: 10.1039/c4nj01358a
4
than that of the Co0.85Se NPs at room temperature. It is believed that the prepared Co0.85Se BNs have
potential applications in catalysis.
www.rsc.org/njc
specific surface area can be used as adsorbents in wastewater
1
. Introduction
6
22
treatment. More recently, tremelliform Co0.85Se nanosheets and
23
In recent years, many effective strategies have been developed polycrystalline Co0.85Se nanotubes have been used as efficient
for the synthesis of transition metal chalcogenides because of catalysts for the decomposition of N . Although Co0.85Se
nanocomposites had been developed
to reduce 4-nitrophenol, the synthesis of Co0.85Se bundle-like
Cobalt selenide, an important transition metal chalcogenide, has nanostructures (BNs) and their efficiency for the catalytic reduction
attracted a great deal of attention because of its good physical and of nitro aromatics by NaBH have been rarely researched.
chemical properties. Thus, Co Se materials with different sizes, In this work, Co0.85Se BNs were prepared using a facile two-step
2 4
H
1
,2
3,4
their potential applications in catalysis,
solar cells,
3 4
gas nanosheets and Co0.85Se-Fe O
5
6
7
18
separation, environmental treatment, and biochemical sensors.
4
x
y
compositions, morphologies, and phase structures have been solvothermal process. Co0.85Se nanoparticles (NPs) were also
prepared through different methods, such as wet chemical obtained using a similar method. The reduction of 4-nitrophenol
8
–11
12,13
14
methods,
thermal decomposition,
laser irradiation,
to 4-aminophenol is a model reaction that has been widely used for
1
5,16
17,18
mechanical alloying,
electrodeposition,
and hydro-/ the quantification and comparison of the catalytic activity of noble
3
,6,19–23
24–28
solvothermal methods.
Co Se micro-/nanostructures have mainly been applied as catalysts NPs were applied as heterogeneous catalysts to reduce 4-nitrophenol
for oxygen reduction reactions.
facile one-step low-temperature hydrothermal approach for the different reaction temperatures. Based on the Arrhenius equation
In previous reports, the obtained metals or their alloys.
Herein, the as-obtained Co0.85Se BNs and
x
9–11
4
Wang and co-workers reported a to 4-aminophenol by NaBH in aqueous solution under three
‡
‡
in situ growth of Co0.85Se on a conductive glass substrate that and Eyring equation, the apparent E , DH , and DS for the Co0.85Se
a
can be utilized as a high-performance counter electrode for dye- BNs and NPs were obtained for the first time, respectively.
3
sensitized solar cells. Recently, Song and co-workers reported
that graphene-like hexagonal Co0.85Se nanostructures with high
2
. Experimental section
a
College of Chemistry and Materials Science, the Key Laboratory of Functional
Molecular Solids, the Ministry of Education, Anhui Laboratory of Molecular-Based
Materials, Anhui Normal University, Wuhu, 241000, P. R. China.
E-mail: konglin@mail.ahnu.edu.cn; Fax: +86 553-3869303
2.1. Synthesis of the Co0.85Se BNs and Co0.85Se NPs
All chemical reagents were analytical grade and were used without
further purification. The Co0.85Se BNs were prepared using a facile
two-step process under solvothermal conditions (Scheme 1, route A).
First, the synthesis of the Co(CO
is summarized as follows: 2 mmol CoCl
were dissolved in a mixed solvent (20 mL H
b
School of Chemical and Engineering, Anhui University of Technology,
Maanshan 243002, P. R. China. E-mail: xwwei@mail.ahnu.edu.cn
Electronic supplementary information (ESI) available: Fig. S1–S6 and Tables S1
3
)
0.35Cl0.20(OH)1.10 BN hard template
Á6H O and 4 mmol urea
O and 20 mL glycerin);
†
and S2. See DOI: 10.1039/c4nj01358a
These authors contributed equally to this work.
2
2
‡
2
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and 318 K, respectively. Furthermore, the representative sample
of the Co0.85Se BNs was also tested for reusability in the
reduction of 4-nitrophenol by NaBH4.
3
. Results and discussion
3.1. Characterization of the Co0.85Se BNs and NPs
In order to obtain the Co0.85Se BNs, we first fabricated the
Co-precursor sacrificial template using a facile solvothermal method
in a mixed solvent. Fig. S1a (ESI†) shows a typical X-ray powder
diffraction (XRD) pattern of the sample that served as the precursor.
Scheme 1 Procedure for the preparation of the Co0.85Se BNs and NPs.
then, the solution was transferred into a Teflon lined stainless
steel autoclave with a capacity of 50 mL and heated at 433 K for
All of the reflection peaks can be indexed to Co(CO
3
)
0.35Cl0.20(OH)1.10
2
3,30
(JCPDS No. 38-0547), which are similar to previous reports.
The
1
0 h. Afterward, the pink precipitates were washed with deionized
water and ethanol several times each and dried under vacuum at
53 K for 5 h. The Co(CO3)0.35Cl0.20(OH)1.10 BNs were then obtained.
Subsequently, the Co0.85Se BNs were synthesized as follows: 100 mg
of Co(CO 0.35Cl0.20(OH)1.10 BNs and 2 mL of freshly prepared NaHSe
Co-precursor with BNs and smooth surface was obtained through
the scanning electron microscopy (SEM) image (Fig. S1b, ESI†).
Moreover, we can clearly see that the bundle-like Co-precursor
assembled with nanorods and grew from the center in a horizontal
direction. Energy dispersive X-ray (EDX) spectroscopy further
confirms the Co-precursor, and the element signals of Co, Cl,
O, and C can be found in Fig. S1c (ESI†).
The phase, crystallinity and purity of the as-obtained Co0.85Se
samples were examined by the XRD technique. Fig. 1a shows the
XRD pattern of the Co0.85Se sample. The characteristic peaks at
3
3
)
solution (1 M) were loaded into a Teflon lined stainless steel
autoclave with 50 mL capacity, and the autoclave was then filled
with ethanol up to 80% of its total volume. The autoclave was heated
at 413 K for 5 h and cooled to room temperature naturally. The black
precipitates were filtered off, washed with deionized water and
absolute ethanol several times each, and dried under vacuum at
2
y values of 33.31, 44.81, and 50.91 correspond to the hexagonal
close packed (hcp) Co0.85Se nanostructure crystal planes of (101),
102), and (110), respectively (JCPDS No. 52-1008). No impurity
3
53 K for 5 h. In addition, the Co0.85Se NPs were also prepared
23
(Scheme 1, route B).
(
peaks from other phases can be detected, indicating that the
precursor has been totally converted into Co0.85Se. The surface
composition and quality of the Co0.85Se samples were deter-
mined by EDX spectrometry and X-ray photoelectron spectra
2
.2. Characterization
The structure, morphology and composition of the products
were characterized by X-ray powder diffraction (XRD, Shimadzu
XRD-6000, Japan), scanning electron microscopy (SEM, Hitachi
S-4800, Japan), and energy dispersive X-ray spectroscopy (EDX,
INCAx-Sight OXFORD) attached to SEM, transmission electron
microscopy (TEM, JEM-2100, 200 kV, Japan), high resolution
TEM (HRTEM), and selected-area electron diffraction (SAED),
respectively. The X-ray photoelectron spectra (XPS) were recorded on
a multifunctional imaging electron spectrometer (Thermo ESCALAB
(XPS) are shown in Fig. 1b–d and Fig. S2 (ESI†). The EDX results
(Fig. 1b) showed that the chemical elements Co and Se were
detected, and the ratio of Co to Se is 45.1 : 54.9. Some C and O
from the air or carbon support films can also be observed. Fig. S2
(ESI†), Fig. 1c and d show the XPS spectrum of the Co0.85Se
sample, which mainly exhibits the peaks of Co2p and Se3d,
respectively, and the ratio of Co to Se is 46.4 : 53.6. The binding
2
50XI, US) with a non-monochromatized Al–MgKa radiation exciting
source. The UV-vis measurements were performed on a U-4100
Hitachi, Japan) spectrophotometer. The Brunauer–Emmett–Teller
(
surface areas and the pore-size distributions were determined by
Nova 2000E (US) at B77 K.
2.3. Catalytic reaction
The catalytic reaction process was similar to that in our previous
29
reports. In a typical catalytic reaction, 10 mL (0. 5 mM) of an
À1
aqueous solution of 4-nitrophenol and 10 mL (0.1 g L ) of an
aqueous dispersion of the Co0.85Se catalyst were mixed, and then
purged with argon for 10 min to remove the dissolved oxygen.
Afterward, 10 mL (0.02 M) of aqueous NaBH solution purged
4
with argon was added to the reaction mixture and time-dependent
absorption spectra were recorded in the UV-vis spectrophotometer
at 298 K. All of the measurements in this investigation were
conducted in triplicate and average values with standard deviation
were determined. In the same way as at 298 K, the reduction
Fig. 1 XRD pattern (a), EDX spectrum (b), XPS spectrum of the Co2p
reaction was also carried out at two other temperatures of 308 K region (c) and Se3d region (d) of the as-obtained Co0.85Se BNs.
6
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Fig. 3 Time-dependent UV-vis absorption spectrum changes for the
reduction of 4-nitrophenol into 4-aminophenol by (a) Co0.85Se BNs and
(
b) Co0.85Se NPs as the catalysts (conditions: 4-nitrophenol, 0.5 mM;
À1
Co0.85Se catalyst, B0.1 g L ; NaBH
4
, 0.02 M; temperature, 298 K).
gradually disappeared with the concomitant appearance of
a new peak at 300 nm, which substantiates the formation of
2
9,32–35
4-aminophenol.
As shown in Fig. 3a, the complete reduction of 4-nitrophenol
Fig. 2 SEM image (a), TEM image (b), HRTEM image (c), and SAED pattern
into 4-aminophenol can be finished within 10 min using
Co0.85Se BNs as the catalyst. However, the conversion time of
(
d) of the as-obtained Co0.85Se BNs.
4
-nitrophenol into 4-aminophenol was within 14 min using the
2
+
energies of B780.8, B779.0, B797.2 and B794.0 eV are Co
same quantity of Co0.85Se NPs as the catalyst (Fig. 3b), which
was lower than that of the Co0.85Se BNs. In this catalytic
reaction, the amount of NaBH was much higher than that of
3
+
2+
3+
2
p3/2, Co 2p3/2, Co 2p1/2 and Co 2p1/2, respectively, which
2
3,31a
are similar to the reported values,
and the binding energy of
4
2
3,31b
À
B55.4 eV is close to the previously reported value for Se3d.
4-nitrophenol and the concentration of BH
4
can be regarded
The morphology and size of the as-obtained Co0.85Se BNs
were further examined by SEM and transmission electron
microscopy (TEM). Fig. 2a shows the SEM image of the products,
which clearly reveals that the as-obtained Co0.85Se product is BNs
with an unsmooth surface. The TEM image (Fig. 2b) further
confirms that the products are BNs with lengths and diameters
of about 1.5 mm and 300 nm. The typical high resolution TEM
as a constant. Thus, the pseudo-first-order kinetics can be
2
4–29,32–35
applied for the evaluation of rate constants.
The linear
relations of ln(C /C ) against time that were observed for the
t
0
Co0.85Se catalysts at three different temperatures are shown in
Fig. 4a and b, and Fig. S5 (ESI†). According to the linear
relationship (Table S1, ESI†), the average reaction rate con-
stants (Table 1) were calculated from three measurements for
each Co0.85Se catalyst at temperatures of 298, 308 and 318 K,
(HRTEM) image in Fig. 2c also shows that the nanorods in the
BNs are composed of domains of nanocrystallites. From the
HRTEM, the lattice spacing is 0.27 nm (Fig. 2c), which can be
indexed to the (101) spacing of hcp Co0.85Se structures (JCPDS
No. 52-1008). Moreover, the corresponding selected-area electron
diffraction (SAED) pattern (Fig. 2d) indicates the polycrystalline
nature of the nanorods, and the diffraction rings can be easily
indexed to the (102), (110), (103), and (112) planes of the hcp
Co0.85Se. As a comparison, the Co0.85Se samples with a particle-
respectively. The catalytic rate of the Co0.85Se BNs at 298 K
À1
(
0.457 min ) was slightly faster than that of the Co0.85Se NPs
À1
À1 18
(0.331 min
3 4
) and Co0.85Se–Fe O nanocomposites (0.3931 min ),
and was much faster than that of the Co0.85Se nanosheets
2
3
like shape (Fig. S3, ESI†) were obtained in the previous report.
3.2. Catalytic performances of the Co0.85Se BNs and NPs
4
-Aminophenol is an important intermediate in the preparation
29,32,33
of paracetamol, acetanilide, phenacetin, and so on.
A series
of noble metal catalysts were developed to reduce 4-nitrophenol
24–28
into 4-aminophenol,
however, the process was much more
costly in this reaction. The reduction reaction was used as a model
system to quantitatively evaluate the catalytic activities of the
Co0.85Se crystals with different morphologies, such as BNs and
NPs. As is well-known, this reaction did not occur without a
catalyst (Fig. S4, ESI†). The typical UV-vis absorption change of the
reaction mixture upon the addition of Co0.85Se BNs and NPs are
shown in Fig. 3a and b, respectively. The colour of the above
mixed solution gradually faded and was ultimately bleached after
Fig. 4 Plots of ln(C
NPs as catalysts at different reaction temperatures of 298, 308, and 318 K;
c) The Arrhenius plots vs. 1000/T and (d) Eyring plots vs. ln(1000/T) for
t 0
/C ) against time for (a) Co0.85Se BNs and (b) Co0.85Se
(
the addition of the Co0.85Se catalysts, and the peak at 400 nm reactions catalyzed by Co0.85Se BNs (I) and Co0.85Se NPs (II), respectively.
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‡
‡
Table 1 Summary of the k, E
a
, DH , and DS for the Co0.85Se BNs and NPs suggest that Co0.85Se catalyst systems are as good as other
as catalysts (conditions: 4-nitrophenol, 10 mL, 0.5 mM; Co0.85Se catalyst,
35
26,36,37
transition metals or noble metal catalysts.
These results
À1
1
0 mL, B0.1 g L ; NaBH
4
, 10 mL, 0.02 M), respectively
indicate that the catalytic performance of Co0.85Se crystals could
be greatly enhanced by controlling the shape, but effectively
improving the stability and percentage recovery of the Co0.85Se
catalysts needs further investigation.
‡
‡
18
T
k
E
a
DH
DS
À1
À1
À1
À1 À1
Samples
(K) (min
)
(kJ mol
)
(kJ mol
)
( J mol
K )
Co0.85Se BNs 298 0.457
14.66
12.15
16.55
42.51
3
3
08 0.513
18 0.673
4. Conclusions
Co0.85Se NPs 298 0.331
17.78
50.66
3
3
08 0.434
18 0.530
Polycrystalline Co0.85Se bundle-like nanostructures have been
successfully synthesized through a facile and effective two-step
hydrothermal method. Based on the Arrhenius equation and
À1 18
(
0.1721 min ). To investigate in more detail, we obtained the Eyring equation at three different temperatures, the activation
‡
‡
apparent E
a
, DH , and DS based on the Arrhenius equation energy, activation enthalpy, and activation entropy of the
/(RT) (Fig. 4c) and Eyring equation ln(k/T) = ln(k /h) + Co0.85Se bundle-like nanostructures and nanoparticles were
ln k = lnA À E
a
B
‡
‡
35
DS /R À DH /(RT) (Fig. 4d), respectively, and a summary of these obtained for the first time. The Co0.85Se bundle-like nanostructures
data are shown in Table S1 (ESI†) and Table 1. It should be noted required a lower activation energy than that of the Co0.85Se
‡
‡
that the Co0.85Se BNs require lower E , DH , and DS than that of nanoparticles for 4-nitrophenol reduction, and as a result, the
a
the Co0.85Se NPs for 4-nitrophenol reduction (Table 1). Here, the Co0.85Se bundle-like nanostructures showed a higher catalytic
Brunauer–Emmett–Teller (BET) surface areas of the Co0.85Se activity than that of the Co0.85Se nanoparticles. Therefore, the good
2
À1
crystals were determined as 15.4 m g for the Co0.85Se BNs, catalytic properties of the Co0.85Se bundle-like nanostructures will
2
À1
and 54.9 m g for the Co0.85Se NPs. However, the Co0.85Se BNs make them attractive for potential applications in the field of
with a small surface-to-volume ratio show a higher catalytic catalysis and other applications.
activity than the Co0.85Se NPs with a large surface-to-volume
ratio in the test. Using the BJH method (Fig. S6, ESI†), the pore
size of the Co0.85Se BNs (B19.7 nm) were found to be larger than
Acknowledgements
the pore size of the Co0.85Se NPs (B17.8 nm). However, the
nitrogen adsorption and desorption measurements (Fig. S6,
ESI†) showed that the pores should come from the crevices in
the 3D structures (Fig. S6a, ESI†) of the Co0.85Se BNs or aggrega-
tion (Fig. S6b, ESI†) of the Co0.85Se NPs. Therefore, the Co0.85Se
BNs with 3D structures provide more excellent channels and
more active sites for the catalytic reduction of 4-nitrophenol, and
as a result, the as-prepared Co0.85Se BNs exhibit a higher activity
This work is financially supported by the National Natural Science
Foundation of China (No. 21071005, 21271006), the Research
Culture Funds of Anhui Normal University (No. 2011rcpy038,
2
(
014xmpy13), the Innovation Funds of Anhui Normal University
No. 2014cxjj13), and the Undergraduate Innovation Training Plan
of Anhui Normal University (No. 201310370080, 201410370199).
for 4-nitrophenol reduction than the Co0.85Se NPs. On the other Notes and references
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