Pd/graphene nanocomposite as highly active catalyst for the Heck reactions

Article abstract of DOI:10.1016/j.apcata.2014.10.044

The graphene-supported Pd (Pd/graphene) catalyst was synthesized using the graphene oxide and Pd salt as precursor; then both Pd nanoparticles and graphene oxide were chemical reduced by hydrazine hydrate. Transmission electron microscope and powder X-ray

Full text of DOI:10.1016/j.apcata.2014.10.044

Accepted Manuscript
Title: Pd/graphene nanocomposite as highly active catalyst for
the Heck reactions
Author: Peiyu Wang Guoheng Zhang Haiyan Jiao liwei Liu
Xiaoyan Deng Yan Chen Xiaoping Zheng
PII:
S0926-860X(14)00667-X
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.apcata.2014.10.044
APCATA 15076
To appear in:
Applied Catalysis A: General
Received date:
Revised date:
Accepted date:
20-5-2014
2-10-2014
15-10-2014
Please cite this article as: P. Wang, G. Zhang, H. Jiao,Liu, X. Deng, Y. Chen, X. Zheng,
Pd/graphene nanocomposite as highly active catalyst for the Heck reactions, Applied
Catalysis A, General (2014), http://dx.doi.org/10.1016/j.apcata.2014.10.044
This is a PDF file of an unedited manuscript that has been accepted for publication.
As a service to our customers we are providing this early version of the manuscript.
The manuscript will undergo copyediting, typesetting, and review of the resulting proof
before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that
apply to the journal pertain.

Pd/graphene nanocomposite as highly active catalyst for the
Heck reactions
Peiyu Wanga*, Guoheng Zhanga, Haiyan Jiaoa,liwei Liua, Xiaoyan Denga, Yan Chena,
Xiaoping Zhengb
a. Key Laboratory for Electronic Materials of the State National Affairs Commission
of PRC, Northwest University for Nationality, Lanzhou, Gansu 730030, China
b. Lanzhou City University, Lanzhou 730070, China
Abstract: The graphene-supported Pd (Pd/graphene) catalyst was synthesized using
the graphene oxide and Pd salt as precursor; then both Pd nanoparticles and graphene
oxide were chemical reduced by hydrazine hydrate. Transmission electron microscope
and powder X-ray diffraction analysis indicated the Pd nanoparticles, which
supported on the surface of the graphene sheets with the size of 2-6 nm. The catalytic
activity of Pd/graphene was investigated in Heck coupling reactions with activated
and non-activated aryl substrates. The Pd/graphene composites exhibit an excellent
catalytic activity, low Pd leaching, and reuse ability of at least five recycles in air for
the Heck carbon-carbon coupling reaction. The experimental results showed the
graphene sheets were great support for ligand-free Pd catalyst.
Keywords: Pd/graphene, Heck reactions, catalytic activity
* Corresponding author. Tel.: +86 931 4872644. E-mail address:wangpy03@126.com (P. W.).
1
Page 1 of 23

1. Introduction
Graphene is a two-dimensional sheet of sp2-hybridized carbon. Because of its
extraordinary thermal, mechanical, and electrical properties, graphene has attracted
much interest both in theoretical studies and applications [1-4]. Its unique properties
endow graphene sheets great potential in many practical applications [5-8]. One
possible route to enlarge its applied field is to incorporate graphene sheets into a
composite material, especially as a support for metal nanoparticles [9].
Metal-graphene composite materials have been used as catalysts for fuel cells [10],
sensors [11], and solar cells [12]. Although metal-graphene composite materials have
high surface areas and stabilities, only a few studies have involved their application as
heterogeneous catalysts in organic reactions [13-17].
In the field of catalysis, Pd is particularly important among the noble metals
[18-20]. Pd supported inorganic materials are known as active catalysts [21-27].
Palladium catalyzed coupling of aryl halides with olefins usually
referred
to
as
Heck
coupling
and
this
is
a
well-established
methodology in modern organic synthesis for the designing new C-C
bond in a target organic molecule [28-32]. The Heck reaction is generally
catalyzed by soluble Pd (II) or Pd (0) complex in solution [28-35]. As many Pd
complexes have problems such as deactivation and difficult separation from solution
due to the aggregation of Pd nanoparticles formed in situ during the Heck reaction [28,
30]. Pd supported on graphene has recently been reported to act as a catalyst in the
Suzuki-Miyaura cross-coupling reaction [15]. But there are few reports about Pd
2
Page 2 of 23

supported on graphene as an active catalyst using in the Heck cross-coupling reactions
[16, 17].
In our present work, we prepared Pd nanoparticles supported in graphene (or
Pd/graphene) via intercalation of metal cations into graphene oxide (GO) layers
followed by chemical reduction of graphene oxide (GO) in water with hydrazine
hydrate [36]. The structure and catalytic properties of the Pd/graphene nanocomposite
were studied. The results indicated that a good dispersion of Pd nanoparticles
(average diameter 3 nm) was distributed in the mono- and few-layered graphene
sheets. The Pd/graphene catalyst exhibits excellent catalytic activities for Heck
carbon-carbon coupling reactions.
2. Experimental details
All the reagents were of analytical grade and were used as received.
2.1. Synthesis of Pd/graphene nanocomposite
Graphene oxide (GO) was prepared from natural graphite using modified
Hummers’ method [37]. Then, aqueous suspension of GO at a concentration of 2
mg/ml was prepared. Next, 100 ml GO suspension was mixtured with 0.03 g PdCl2
under the assistant of mild ultrasound, hydrazine hydrate (2.00 mL, 64 mmol) was
o
then added and the solution heated in an oil bath at 100 C under a water-cooled
condenser for 1 h over which the reduced GO gradually precipitated out as a black
solid. This product was isolated by filtration over a medium fritted glass funnel,
washed copiously with water (5 · 100 mL) and methanol (5 · 100 mL), and then dried
o
in a vacuum oven at 60 C. For comparison, 100 ml GO suspension was reduced by
3
Page 3 of 23

hydrazine hydrate using the same method and the resulting sample was denoted as
graphene.
2.2. Catalytic testing
A typical experiment for the Heck coupling reaction was performed in a
round-bottomed flask without any special precaution to exclude air or moisture. 20
mmol aryl halide, 20 mmol vinyl substrate, 24 mmol K2CO3, 1 g decane (as internal
standard for gas chromatography analysis), and 0.05 or 0.1 mol% Pd (relative to aryl
halide) were added to solvent NMP (20 ml). The mixture was magnetically stirred at
100 C for 1 h to 3 h. The products were analyzed by a Varian Cp-3380 gas
chromatography (GC) using a flame ionization detector (FID). For isolation of
products at the end of catalytic reaction, the catalyst was separated by filtration; and
then the filtrate was poured into water and extracted with CH2Cl2. The combined
organic extracts were dried using anhydrous MgSO4. The purified products were then
isolated by column chromatography over silica gel and analyzed by GC-MS and
liquid NMR measurements. The liquid NMR was conducted on mercury plus-400 (1H:
300Hz, 13C: 75Hz) with CDCl3 as solvent. GC mass spectra were measured on
Thermo Finnigan Trace DSQ. The recovering catalyst was washed three times with
10 ml water and three times with 10 ml ethanol, and then dried for the next run.
2.3. Instrumentation
Pd elemental analysis of the nanocomposites was performed on a Thermo IRTS
advantage ICP-AES. N elemental analyses of the nanocomposites were performed on
a VarioEL CHNS elemental analyzer. The X-ray powder diffraction (XRD)
experiments were carried out on a Rigaku D/Max-2400 X-ray diffractometer using Cu
K radiation. CO chemisorption measurements were taken at 298 K using a
homemade pulse flow system. Prior to measurements, samples were subjected to a
4
Page 4 of 23

pretreatment involving exposure to hydrogen flow for 1 h at 300C, then the sample
was cooled down to room temperature in pure N2 stream. The transmission electron
microscopy (TEM) observations of the Pd/graphene nanocomposite were carried out
on a JEM 2010 operating at an acceleration voltage of 200 kV. Nitrogen
adsorption-desorption isotherms were measured by a NOVA 2000e surface area and
pore size analyzer. The specific surface areas were evaluated using
Brunauer-Emmett-Teller (BET) method. Pore size distribution was calculated using
the Barrett-Joyner-Halenda (BJH) method based on the adsorption branch of the
isotherms, and the pore size was reported from the peak position of the distribution
curve. The pore volume was taken from a single-point adsorbed volume at a relative
pressure P/P0 of 0.97.
3. Results and discussion
3.1 Physicochemical studies
Fig. 1 shows the XRD pattern of the as-prepared Pd/graphene composite. The
peaks appeared at 40.1º, 46.7º, 68.1º, and 82.0º can be assigned to the diffraction of
(111), (200), (220) and (311) plane of the face-centered cubic palladium (JCPDS No.
46-1043) respectively [38]. The average grain size of the Pd nanoparticles in the
nanocomposites was estimated from the full width at half maximum of the diffraction
peaks using Scherrer equation. The average particles size of the Pd nanoparticles was
3 nm for Pd/graphene composite. The Pd loadings in the Pd/graphene nanocomposite
samples determined by the elemental analysis is 7.8 wt%. Pd dispersion (D) and metal
surface area of Pd/graphene measured by CO chemisorption are 36% and 161 m2/g.
The calculated Pd particle size (d) of Pd/graphene based on this method is 3 nm (d =
5
Page 5 of 23

1.12/D) [39, 40], which is in good agreement with TEM observation. This indicates
that Pd nanoparticles in Pd/graphene are highly dispersed in the surface of graphene.
Fig. 2a was the typical TEM image of the Pd/graphene composite. It can be seen
that Pd nanoparticles which supported on the surface of the graphene sheets, are
composed of spherical particles. The size of the Pd particles observed in the TEM
image is the range of 2-6 nm. No agglomeration is observed. It is interesting to note
that Pd nanoparticles and graphene are not present as separate constituents. The Pd
particle size distribution in the nanocomposites is shown in Fig. 2b. The mean particle
size determined from the particle size distribution is 3 nm. The coincidence of the
average grain size estimated from the XRD analysis and the mean particle size
determined from the TEM analysis indicate that the Pd nanoparticles in Pd/graphene
are single crystals.
Raman spectra of graphene and Pd/graphene are shown in Fig.3. The two bands
sat about 1358 and 1596 cm-1 are assigned to the disorder induced D-band and
in-phase vibration of the graphene lattice (G-band), respectively [41]. Features of
Raman spectra of several metal-decorated graphene materials were analyzed in detail
by Subrahmanyam et al [42]. The D-band originates from defects of graphene and it is
absent in Raman spectra of defect-free samples. The G-band corresponds to the E2g
mode, which results from the vibration of sp2 bonded carbon atoms. When Au, Ag, Pt
and Pd nanoparticles were deposited on graphene, the intensity of the D-band
increased relative to the G-band and G bands shifted to higher wavenumbers [42, 43].
From these features of Raman spectra, the presence of electronic interaction between
the metal particles and graphene was inferred. In the present study, the intensity ratio
of D and G bands for RGO (Fig. 3, curve i) is 0.94, whereas this ratio for Pd/graphene
(Fig. 3, curve ii) is 1.12. Furthermore, there is a shifted of G-band from 1596 cm-1 in
6
Page 6 of 23

graphene to 1560 cm-1 in Pd/graphene [43]. These results suggest the existence of
electronic interaction between Pd and graphene in Pd/graphene.
The nitrogen adsorption-desorption isotherms and the BJH pore size distribution
(based on adsorption branch of the isotherms) for all the samples are shown in Fig. 4.
The isotherms are characterized by the type IV with a H1-type hysteresis loop defined
by IUPAC [44]. This type of hysteresis loop is associated with capillary condensation
and desorption in open-ended cylindrical mesopores [44]. Hysteresis loops with the
similar shapes showing the absence of pore clogging. A specific surface area of 463
m2/g and a pore volume of 0.52 cm3/g are obtained from the isotherm of Pd/graphene.
The nitrogen adsorption isotherm study (Fig.4b) shows that the Pd/graphene is
mes-oporous and the pore size distribution lies in 2-50 nm range and most of pores
are focus on about 3 nm.
3.2. Catalytic characteristics of Pd/graphene
Pd/graphene is applied to catalyze the Heck carbon-carbon coupling reaction of
aryl halides. The reactions are performed in NMP with K2CO3 as a base. The
reactions were conveniently carried out in batch reactors in air at 100C (Table 1).
The products obtained were only cis-isomer and trans-isomer in all the cases. The
conversions for the aryl halides and the selectivity with respect to the reaction time
and amount of catalyst are listed in Table 1.
Extension of the reaction to 1-iodo-4-nitrobenzene with n-Butyl acrylate or
styrene afforded the high yields as shown in Table 1 (Table 1, entry 1 and entry 2).
0.05 mol% Pd of Pd/graphene used in coupling reactions of iodobenzne with n-butyl
acrylate at 100C for 1.5 h and styrene at 100C for 2.5 h also show high activities
7
Page 7 of 23

(Table 1, entry 3 and entry 4). Extension of the reaction to 1- bromo-4-nitrobenzene
also afforded the high yields as shown in Table 1(Table 1, entry 5 and entry 6). As
1-bromo-4-nitrobenzene is a more reactive reactant than bromobenzene in the
arylation reaction with n-butyl acrylate or styrene as the substrate; bromobenzene is
used as reactant with styrene and n-butyl acrylate, more catalyst (0.1 mol% Pd) are
required to achieve high yields (entry 7 and 8 in Table 1). A conversion of 96 % with
a yield of 93 % for bromo-benzene with n-butyl acrylate (Table 1, entry 7) and a
conversion of 93 % with a yield of 90 % for bromo-benzene with styrene (Table 1,
entry 8) have been achieved. However, chlorobenzene afforded relatively lower
coupling products (Table 1, entry 9 and entry 10) even taking more time than that of
other aryl bromides (Table 1, entry 1 to entry 8). Compared to the analogous catalyst
such as Pd/Graphene oxide [16], Pd@PRGO [17], Pd PdNs-PAMAM
(G3)-g-MWCNTs [22] and Pd/HCN [26], Pd/graphene shows comparable yield or
even more yield in Heck reaction of iodobenzene with styrene using less catalyst
(Table 2). These results showed that the Pd/graphene catalyst had high activity in the
Heck reaction (Table 2).
In order to make sure that the catalysis runs are based on heterogeneous pathway,
the reaction experiment of 1-iodo-4-nitrobenzene with n-butyl acrylate was made in a
manner similar to the general procedure for the Heck reactions, but with the exception
that the catalyst was filtered off after approximately 20% conversion. The resulting
solution was heated under the identical reaction condition for an additional 2 h and
analyzed for further conversion. No further reaction is detected after the catalyst
removal. This result indicates that Heck reactions investigated follow a heterogeneous
8
Page 8 of 23

pathway.
The Pd/graphene catalyst recycling investigations were performed using the
reaction of bromobenzene with n-butyl acrylate by recycling and then reusing the
catalyst under the same conditions. As showed in Table 3, this Heck coupling of
bromobenzene and n-butyl acrylate exhibits high conversion at least up to 90% until
fifth recycling usage of the Pd/graphene catalyst. The catalyst Pd/graphene can be
reused and keeps its high catalytic activity in catalyst recycling for the Heck reactions.
Detailed studies were carried out on Pd/graphene that had been recovered after
fifth recycles in the reaction between bromobenzene and n-butyl acrylate. The Pd
loadings of the used catalyst is 7.5 wt% after fifth recycling usage which was about
3.85% lower than the fresh catalyst indicating loss of palladium. CO chemisorption of
the used catalyst shows that there are a little decrease in metal dispersion and metal
surface (metal dispersion 29 % and metal surface area 129 m2/g, compared to 36%
and 161 m2/g of fresh catalyst). These indicate that there are a little metal aggregation
after five recycles. From the investigations above, there are both low Pd leaching and
a little metal aggregation during the reactions which both cause the drop of the
catalytic activity in the recycle reactions.
4. Conclusions
Pd/graphene can be prepared via intercalation of metal cations into graphene
oxide layers; then both Pd nanoparticles and graphene oxide were chemical reduced
by hydrazine hydrate. The Pd nanoparticles with 2-6 nm are distributed in the
graphene nanosheets without any agglomeration. The catalytic activity of Pd/graphene
was investigated for Heck coupling reactions. The Pd/graphene nanocomposite
exhibited an excellent catalytic activity, high reuse ability, and low Pd leaching in air
9
Page 9 of 23

for the Heck reaction, and hence, is an efficient heterogeneous catalyst.
Acknowledgments
This work was supported by the National Natural Science Foundation of China (Grant
No. 11164012 and 51462031) and the National Natural Science Foundation of Gansu
Province (Grant No. 145RJZA218 and 145RJZA097). This work was also supported
by the Introduction of Talent project of Northwest University for Nationality (Grant
No. xbmuyjrc201307).
References:
[1] J. C. Meyer, A. K. Geim, M. I. Katsnelson, K. S. Novoselov, T. J. Booth, S. Roth,
Nature 446 (2007) 60-63.
[2] L. A. Ponomarenko, F. Schedin, M. I. Katsnelson, R. Yang, E. W. Hill, K. S.
Novoselov, A. K. Geim, Science 320(2008)356-358.
[3] K. S. Novoselov, Z. Jiang, Y. Zhang, S. V. Morozov, H. L. Stormer, U. Zeitler, J.
C. Maan, G. S. Boebinger, P. Kim, A. K. Geim, Science 315(2007)1379-1379.
[4] K. S. Novoselov, A. K. Geim, S. V. Morozov, D. Jiang, Y. Zhang, S. V. Dubonos,
I. V. Grigorieva, A. A. Firsov, Science 306(2004)666-669.
[5] L. M. Xie, X. Ling, Y. Fang, J. Zhang, and Z. F. Liu, J. Am. Chem. Soc. 13 (2009)
9890-9891.
[6] D. Y. Pan, S. Wang, B. Zhao, M. H. Wu, H. J. Zhang, Y. Wang, Z. Jiao, Chem.
Mater. 21 (2009) 3136-3142.
[7] Y. Wang, Z. Q. Shi, Y. Huang, Y. F. Ma, C. Y. Wang, M. M. Chen, Y. S. Chen, J.
Phys. Chem. C 113(2009) 13103-13107.
[8] M. Müller, J. Schmalian, L. Fritz, Phys. Rev. Lett. 103 (2009) 025301-025304.
[9] S. Stankovich, D. A. Dikin, G. H. B. Dommett, K. M. Kohlhaas, E. J. Zimney, E.
10
Page 10 of 23

A. Stach, R. D. Piner, S. T. Nguyen, and R. S. Ruoff, Nature 442 (2006) 282-286.
[10] E. Yoo, T. Okata, T. Akita, M. Kohyama, J. Nakamura, I. Honma, Nano Lett.
9(2009)2255-2259.
[11] J. L. Johnson, A. Behnam, S. J. Peartonand, A. Ural, Adv. Mater.
2010(22)4877-4880.
[12] X. Wang, L. J. Zhi, K. Mullen, Nano Lett. 8(2008)323-327.
[13] A. Mastalir, T. Szabo, Z. Kiraly, I. Dekany, Catal. Commun., 17(2012) 104-107.
[14] Y. Li, X. B. Fan, J. J. Qi, J. Y. Ji, S. L.Wang, G. L. Zhang, F. B. Zhang, Nano
Res. 3(2010)429-437.
[15] Y. Nishina, J. Miyata, R. Kawaib, K. Gotoh. RSC Advances 2(2012)9380-9382.
[16] Yu. V. Ioni, S. E. Lyubimov, V. A. Davankov, S. P. Gubin, Russian Journal of
Inorganic Chemistry, 58(2013) 392-394.
[17] S. Moussa, A. R. Siamaki, B. F. Gupton, M. S. El-Shall, ACS Catal.,
2(2012)145-154.
[18] L. Q. Xue, Z. Y. Lin, Chem. Soc. Rev. 39(2010)1692-1705.
[19] H. U. Blaser, A. Indolese, A. Schnyder, H. Steiner, M. Studer, J. Mol. Catal. A:
Chem. 173(2001) 3-18.
[20] L. X. Yin, J. Liebscher, Chem. Rev. 107(2007)133-173.
[21] M. Hosseini-Sarvari, Z. Razmi, M. M. Doroodm, Applied Catalysis A: General
475 (2014) 477-486.
[22] M. R. Nabid, Y. Bide, S. J. T. Rezaei, Applied Catalysis A: General 406 (2011)
124-132.
11
Page 11 of 23

[23] R. B. Bedford, U. G. Singh, R. I. Walton, R. T. Williams, S. A. Davis, Chem.
Mater. 17 (2005)701-707.
[24] R. Nie, J. Shi, W. Du, Z. Hou, Applied Catalysis A: General 473 (2014) 1-6.
[25] A. Gniewek, J. J. Ziolkowski, A. M. Trzeciak, M. Zawadzki, H. Grabowska, J.
Wrzyszcz, J. Catal. 254(2008)121-130.
[26] M. Zhu, Y. Wang, C. Wang, W. Li, G. Diao, Catal. Sci. Technol. 2013(3)
952-961.
[27] S.-J. Kim, S.-D. Oh, S. Lee, S.-H. Choi, J. Ind. Eng. Chem. 2008(14)449-456.
[28] F. Zhao, K. Murakami, M. Shiraia, M. Arai, J. Catal. 194(2000) 479-483.
[29] P. Veerakumar, M. Velayudhamb, K.-L. Lub, S. Rajagopala, Applied Catalysis A:
General 455 (2013) 247-26.
[30] M. T. Reetz, J. G. de Vries, Chem. Commun. (2004) 1559-1563.
[31] C. Amatore, A. Jutand, Acc. Chem. Res. 33 (2000) 314-321.
[32] C. Rocaboy, J.A. Gladysz, Org. Lett. 4 (2002) 1993-1996.
[33] A. V. Martínez, J. A. Mayoral, J. I. García, Applied Catalysis A: General 472
(2014) 21-28.
[34] X. Yang, Z. Fei, D. Zhao, W.H. Ang, Y. Li, P.J. Dyson, Inorg. Chem. 47 (2008)
3292-3297.
[35] I. P. Beletskaya, A. N. Kashin, I. A. Khotina, A. R. Khokhlovc, Synlett. 10
(2008)1547-1552.
[36] S. Stankovich, D. A. Dikin, R. D. Piner, K. A. Kohlhaas,A. Kleinhammes, Y. Jia,
Y. Wu,S. T. Nguyen, R S. Ruoff. Carbon 45 (2007) 1558-1565.
12
Page 12 of 23

[37] B. Luo, X. Yan, S. Xu, Q. Xue, Electrochim. Acta 59 (2012)
429.
[38] H. L. Su, Q. Dong, J. Han, D. Zhang, Q. X. Guo, Biomacromolecules 9 (2008)
499-504.
[39] N. Mahata, V.Vishwanathan J. Catal. 196 (2000)262-270.
[40] S. H. Ali, J. G. Goodwin, J. Catal. 176 (1998)3-13.
[41] Y. Li, X. Fan, J. Qi, J. Ji, S. Wang, G. Zhang, F. Zhang, Mater. Res. Bull., 2010
(45) 1413-1418.
[42] K. S. Subrahmanyam, A. K. Manna, S. K. Pati,. N. R. Rao, Chem. Phys. Lett.,
2010(497)70-75.
[43] S. Kumar, C. Selvaraj, N. Munichandraiah, L. G. Scanlonb, RSC Adv.2013(3)
21706-21714.
[44] K. S. W. Sing, D. H. Everett, R. A. W. Haul, L. Moscou, R. A. Pierotti, J
Rouquerol, T. Siemieniewska. Pure Appl. Chem. 57(1985)603-619.
13
Page 13 of 23

Table 1 Heck olefination of aryl halide by Pd/graphene a
Conversion
(%)
100
100
100
100
100
100
96
Entry
R
X
Vinyl substrate
t (h)
Yieldsb (%) of trans
1
2
NO2
NO2
H
I
n-Butyl acrylate
Styrene
1
3
98
98
98
98
97
96
93
90
35
24
I
3
I
n-Butyl acrylate
Styrene
1.5
2.5
1.5
2
4
H
I
5
NO2
NO2
H
Br
Br
Br
Br
Cl
Cl
n-Butyl acrylate
Styrene
6
7 c
8 c
9c
10c
n-Butyl acrylate
Styrene
3
H
3
93
H
n-Butyl acrylate
Styrene
24
24
37
H
26
a. Pd in the Pd/graphene nanocomposite is 0.05 mol% relative to the amount of aryl
halides.
b. Isolated yield was based on the aryl halide used.
c. Pd in the Pd/graphene nanocomposite is 0.1 mol% relative to the amount of aryl
halides.
14
Page 14 of 23

Table 2 Catalytic performance of different supported Pd-based catalysts in the
coupling reaction of iodobenzene and styrene
Amont
(mol%)
Yields
(%)
Entry
Catalyst
Solvent
Toluene
Base
NEt3
T(oC)
Reflux
180a
t (h)
5
Ref.
16
Pd/Graphene
oxide
1
2
3
0.54
0.5
62
95
95
Pd@PRGO
H2O:EtOH
= 1 : 1
K2CO3
K2CO3
1/6
2.5
17
PdNs-PAMAM
-g-MWCNTs
Pd/HCN
NMP
0.3
100
22
4
5
DMF
NMP
K2CO3
K2CO3
0.255
0.05
120
100
1
100
98
26
Pd/graphene
2.5
This work
a. The temperature was obtained by microwave irradiation
15
Page 15 of 23

Table 3 Effect of recycling on the catalytic efficiency of Pd/grgaphene a.
Run number
1
2
3
4
5
6
7
Conversion (%)
96
95
95
93
90
85
80
a. Reaction conditions: 20 mmol bromobenzene, 20 mmol n-butyl acrylate,
24 mmol K2CO3, 20 ml NMP, 100 ◦C, 0.1 mol% Pd/graphene, 3 h.
16
Page 16 of 23

List of figure captions:
Fig. 1. XRD pattern of the Pd/graphene.
Fig. 2. TEM micrograph of the Pd/graphene (a) and the corresponding Pd particle size
distribution (b).
Fig. 3. Raman spectra of graphene and Pd/graphene.
Fig. 4. Nitrogen adsorption-desorption isotherms of Pd/graphene (a) and the pore size
distribution curve.
17
Page 17 of 23

Fig.1
18
Page 18 of 23

Fig.2
19
Page 19 of 23

Fig.3
20
Page 20 of 23

Fig.4
21
Page 21 of 23

22
Page 22 of 23

>Pd nanoparticles were supported on the surface of the graphene sheets. >The size of
Pd nanoparticles was about 3 nm. > The Pd/graphene nanocomposite exhibited an
excellent catalytic activity, high reuse ability, and low Pd leaching in air for the Heck
reaction. > Pd/graphene is an efficient heterogeneous catalyst.
23
Page 23 of 23