RuPd alloy nanoparticles supported on N-doped carbon as an efficient and stable catalyst for benzoic acid hydrogenation

Article abstract of DOI:10.1021/acscatal.5b00037

RuPd alloy nanoparticles (3.6 nm) uniformly dispersed on N-doped carbon (RuPd/CN) was prepared via a simple ultrasound-assisted coreduction method. The RuPd/CN is highly active, selective, and stable in the hydrogenation of benzoic acid to cyclohexanecarboxylic acid under mild conditions with a TOF up to 2066 h^-1. It was found that the bimetallic RuPd/CN catalyst exhibited a substantially enhanced activity in comparison with the monometallic catalysts (Ru/CN and Pd/CN). The reason for the higher performance of the RuPd/CN catalyst is considered to be the increased Ru⁰ /Ruⁿ⁺ ratio induced by the electronic interaction between Ru and Pd, as evidenced by various characterizations. Notably, the different phenomenon of activity platform on different catalysts ascribed to the effect of hydrogen pressure was newly observed and further explained by first-principle studies. Moreover, the factors influencing the adsorption modes of BA, especially the configuration of the carboxyl group, have been investigated preliminarily in first-principle studies, giving a distinct insight from the former work. The reason the carboxyl group in benzoic acid does not undergo hydrogenation, which results in superior selectivity (>99%), is also revealed by a comparison of the thermodynamics of hydrogenation and dissociation of the carboxyl group.

Full text of DOI:10.1021/acscatal.5b00037

Subscriber access provided by ECU Libraries
Article
RuPd Alloy Nanoparticles Supported on N-Doped Carbon as an
Efficient and Stable Catalyst for Benzoic Acid Hydrogenation
Minghui Tang, Shanjun Mao, Mingming Li, Zhongzhe Wei, Fan Xu, Haoran Li, and Yong Wang
ACS Catal., Just Accepted Manuscript • DOI: 10.1021/acscatal.5b00037 • Publication Date (Web): 14 Apr 2015
Downloaded from http://pubs.acs.org on April 19, 2015
Just Accepted
“Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted
online prior to technical editing, formatting for publication and author proofing. The American Chemical
Society provides “Just Accepted” as a free service to the research community to expedite the
dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts
appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been
fully peer reviewed, but should not be considered the official version of record. They are accessible to all
readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered
to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published
in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just
Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor
changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers
and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors
or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
ACS Catalysis is published by the American Chemical Society. 1155 Sixteenth Street
N.W., Washington, DC 20036
Published by American Chemical Society. Copyright © American Chemical Society.
However, no copyright claim is made to original U.S. Government works, or works
produced by employees of any Commonwealth realm Crown government in the course
of their duties.

Page 1 of 26
ACS Catalysis
1
2
3
4
5
6
7
8
9
RuPd Alloy Nanoparticles Supported on N-Doped
Carbon as an Efficient and Stable Catalyst for
Benzoic Acid Hydrogenation
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Minghui Tang, Shanjun Mao, Mingming Li, Zhongzhe Wei, Fan Xu, Haoran Li and Yong Wang*
Advanced Materials and Catalysis Group, ZJU-NHU United R&D Center, Department of
Chemistry, Zhejiang University, Hangzhou 310028, P. R. China
KEYWORDS: Bimetallic catalyst, RuPd alloy, N-doped carbon, Chemoselective hydrogenation,
Benzoic acid
ABSTRACT: RuPd alloy nanoparticles (3.6 nm) uniformly dispersed on N-doped carbon
(RuPd/CN) was prepared via a simple ultrasound-assisted co-reduction method. The RuPd/CN is
highly active, selective and stable in the hydrogenation of benzoic acid to cyclohexane
-1
carboxylic acid under mild conditions with a TOF up to 2066 h . It was found that the bimetallic
RuPd/CN catalyst exhibited a substantially enhanced activity compared with the monometallic
catalysts (Ru/CN and Pd/CN). The reason for higher performance of the RuPd/CN catalyst is
0
n+
considered to be the increased Ru /Ru ratio induced by the electronic interaction between Ru
and Pd as evidenced by various characterizations. Notably, the different phenomenon of activity
platform on different catalysts ascribed to the effect of hydrogen pressure was newly observed
and further explained by the first-principle studies. Moreover, the factors influencing the
ACS Paragon Plus Environment
1

ACS Catalysis
Page 2 of 26
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
adsorption modes of BA, especially the configuration of the carboxyl group are investigated
preliminarily in first-principle giving a distinct insight from the former work. The reason why the
carboxyl group in benzoic acid does not undergo hydrogenation, which results in the superior
selectivity (>99%), is also revealed by the comparison of the thermodynamics of hydrogenation
and dissociation of the carboxyl group.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
. INTRODUCTION
Cyclohexane carboxylic acid (CCA) is an important organic intermediate for the synthesis of
1
pharmaceuticals, such as praziquantel, hexanolactam and ansatrienin. Chemoselective
2
hydrogenation of benzoic acid (BA) is the most effective method to obtain CCA (Scheme 1).
However, aromatic ring hydrogenation requires more severe conditions than those required to
hydrogenate other functional groups (typically, C=O, C=C, or C=N etc.) due to the need to
3
overcome the high resonance energy of benzene ring.
Scheme 1. Products from divergent pathways of hydrogenation of BA.
OH
O
OH
OH
O
H2
+
Catalyst
Benzoic acid
BA
Cyclohexane carboxylic acid
CCA
Benzyl alcohol
4
Traditionally, hydrogenation of BA has been carried out by using stoichiometric Na-K alloys.
It also has been found that CCA can be produced from hydrogenation of molten BA without any
solvent over carbon-supported precious metals catalyst. Unfortunately, the reaction was usually
ACS Paragon Plus Environment
2

Page 3 of 26
ACS Catalysis
1
2
3
4
5
6
7
8
9
carried out in scCO or under high H pressures (10~15 MPa) and high temperatures (150~200
2
2
o
5
C). Thus, preparing a high-performance and environmentally friendly catalyst used under mild
reaction conditions for the chemoselective hydrogenation of BA is urgently needed.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
In recent years, researchers have found that Pd can be used for selective hydrogenation
6
reactions. Activity of Pd catalysts can be controlled by varying the support materials (MgO,
7
8
9
10
11-14
Al O , activated carbon, TiO , MCM-41, mpg-C N etc.
). As carbon materials are
2
3
2
3
4
mainly composed of carbon and even can be made directly out of biomass, they are obviously
1
5
“sustainable” support materials for Pd nanoparticles (NPs). However, as reported by Anderson,
the carbon supported Pd catalyst also presented a poor activity toward the aromatic ring
hydrogenation, the activated carbon supported Pd (Pd/AC) converted only 34% BA to CCA after
o
16
24 h using 1 bar hydrogen at 85 C. Furthermore, Pd deposited on carbons easily leaches during
catalytic processes because the interaction between the metal and the carbon surface is weak. As
a consequence, the chemical or catalytic properties of carbons do not always satisfy the sharply
increasing demands of catalysis. The recent fast-growing research upon porous carbon materials,
especially the nitrogen doped carbon, with enhanced chemical, electrical and functional
1
7-24
properties, demonstrated as a novel support for heterogeneous catalysis.
Indeed, we showed earlier that Pd NPs supported on a N-doped carbon (Pd/CN) catalysed BA
o
hydrogenation efficiently, obtaining 100% yield of CCA at 85 C under 1 bar H pressure after
2
2
5
24 hours. However, the high price of noble metal catalysts has limited their further application
in industry. Therefore, it is desired to search out a suitable substitute for Pd having lower cost but
comparable activity for the BA hydrogenation. Alloying with a second metal is considered to be
2
6-28
effective for obtaining a highly active catalyst.
In addition, the dilution of costly noble metals
ACS Paragon Plus Environment
3

ACS Catalysis
Page 4 of 26
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
by inexpensive metals in bimetallic catalysts is also of interest because of the potential savings in
2
9-33
material cost, while still maintaining or even enhancing the catalytic performance.
Herein, considering of the bimetallic effects and the advantage of lowering the cost of catalyst,
we prepared bimetallic RuPd/CN catalyst, and tested its activity in the hydrogenation of BA. We
found that bimetallic catalyst RuPd/CN exhibited higher activity than monometallic catalysts
Ru/CN and Pd/CN. An obvious electronic interaction between Ru and Pd was observed through
XPS, verifying the reason for better catalytic behavior of bimetallic catalyst in the hydrogenation
reaction. The intrinsic alloy synergistic effects on the catalyst structure and catalysis behavior
were investigated in deep both experimentally and theoretically. Furthermore, the as-synthesized
RuPd/CN not only exhibits higher activity, but also better stability towards BA hydrogenation,
when compared with Pd/CN, Ru/CN and commercial Pd/AC catalysts.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
2
. RESULTS AND DISCUSSION
We have reported that Pd/CN showed higher catalytic performance in BA hydrogenation to
25
CCA than other supported Pd catalysts (Pd/AC, Pd/metal oxide, etc). The performance of
various Pd/CN catalysts modified with inexpensive metals (Ru, Cu, Fe, Ni and In) was compared
as shown in Table 1. In the bimetallic catalysts, the loading of Pd was fixed at 1 wt. %; the
amount of additive metal was fixed at 2.5 by the weight ratio of the additive to Pd, which is the
best composition for RuPd/CN (Table S1). Notably, RuPd/CN showed the highest BA
conversion, even compared with Pd/CN. Unfortunately, other MPd/CN (M=Cu, Fe, Ni, and In)
all showed very poor activity. Furthermore, the performance of various metals (Ru, Cu, Fe, Ni
and In) modified Ru/CN catalysts was also compared. As might be expected, RuPd/CN showed
the highest BA conversion, but other RuM/CN (M= In, Fe, Cu, and Ni) showed relatively poor
ACS Paragon Plus Environment
4

Page 5 of 26
ACS Catalysis
1
2
3
4
5
6
7
8
9
activity. From a catalytic point of view, the RuPd/CN catalyst already appears as quite a unique
and interesting material. Next, a series of characterizations and activity tests accompanied by
theoretical calculations had been carried out to explain the experimental results and find out the
relationship between bimetallic catalyst intrinsic alloy synergistic effect and catalytic properties.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Table 1. Comparison of the catalytic performances in the BA hydrogenation over modified
a
Pd/CN (1 wt. % Pd, secondary metal/Pd=2.5) and modified Ru/CN (1 wt. % M, M/Pd=2.5).
Entry Catalyst Conversion/% and (selectivity %)
1
2
3
4
5
6
7
8
9
Pd/CN
CuPd/CN
FePd/CN
NiPd/CN
InPd/CN
RuPd/CN
Ru/CN
38(100)
0
0
0
0
67(100)
9(100)
0.2(100)
10(100)
11(100)
4(100)
RuIn/CN
RuFe/CN
RuNi/CN
RuCu/CN
1
0
1
1
a
o
Reaction conditions: BA 0.5 mmol, catalyst 50 mg, solvent water 25 mL, 85 C, 0.1MPa H , 6
2
hours.
In order to highlight the advantage of N-doped carbon as support, a variety of non-nitrogen
carbon (non-nitrogen hydrothermal carbon, HC; commercial active carbon, AC; commercial
multi-wall carbon nanotubes, CNT) are used to compare with CN under identical conditions
ACS Paragon Plus Environment
5

ACS Catalysis
Page 6 of 26
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
(
Table 2). The textural properties of the different catalysts are listed in Table S2. Among the
different catalysts, RuPd/CN was found to give the most active system (Table 2, entry 1). To
clarify, the HC (from glucose) was prepared using the same method as CN (D-glucosamine
hydrochloride). RuPd/HC resulted in a BA conversion of only 28%, meaning the N atoms in
RuPd/CN are of crucial importance on the catalytic activity. Thus, N-doped carbon materials as
high-performance catalyst supports have great promising application in heterogeneous catalysis.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
a
Table 2. Catalytic results for different catalysts.
Entry
Catalyst
RuPd/CN
RuPd/HC
RuPd/AC
RuPd/CNT
Conversion/% and (selectivity / %)
1
2
3
4
67(100)
28(100)
45(100)
39(100)
a
o
Reaction conditions: BA 0.5 mmol, catalyst 50 mg, solvent water 25 mL, 85 C, 0.1MPa H , 6
2
hours.
The mesoporous structure of the support and various catalysts were identified by nitrogen
adsorption/desorption isotherms (Figure S4, Table S2). The results clearly show the support CN
retained its mesoporosity well after the loading of monometallic or bimetallic nanoparticles,
indicating that the CN was an excellent support.
To better understand the catalytic properties of supported bimetallic catalysts, it is necessary to
explore both the distribution and the chemical states of the metals within the individual NPs. The
dispersion and the average metal particle size of the RuPd/CN were confirmed by HRTEM
ACS Paragon Plus Environment
6

Page 7 of 26
ACS Catalysis
1
2
3
4
5
6
7
8
9
(
Figure 1). It revealed that the NPs were uniformly dispersed on the support, no significant
aggregations were observed, which may result from the excellent anchoring of the CN towards
1
5
the deposited NPs due to the electronegative nitrogen in the carbon structure. For the Pd/CN,
the metal particles had an average size of 4.6 nm with a range of 2~8 nm (Figure S5), while
RuPd/CN exhibited a smaller particle size (3.6 nm) and a relatively narrow particle size
distribution (2~5 nm), indicating that the introduction of Ru could effectively improve the Pd
dispersion. Figure 1 (C) shows the particles were highly faceted. The nanocrystal plane spacing
was measured as 0.199 nm, which locates between the Ru (111) of 0.129 nm and the Pd (111) of
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
0
.224 nm. Furthermore, no separated Ru or Pd lattice was detected, which demonstrated Ru and
Pd distributed homogenously in the particles of RuPd/CN.
In addition, STEM analysis was performed to clarify the structural and compositional details
of RuPd NPs (Figure 2). The color distribution in HAADF images showed that the Ru and Pd X-
ray signals completely homogeneous cover the spatial area of the NPs, suggesting that the alloy
has been formed. EDX line scanning analysis of two optionally neighbored RuPd NPs further
verified the formation of atomic-level RuPd alloy.
ACS Paragon Plus Environment
7

ACS Catalysis
Page 8 of 26
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Figure 1. HRTEM images (A, B and C) and particle size distribution (D) of RuPd/CN.
Figure 2. (A) HAADF-STEM image, (B) Pd-L and (C) Ru-L STEM-EDX map obtained from a
group of RuPd NPs of RuPd/CN. (F) Reconstructed overlay images of the maps shown in panels
(
B) and (C), red, Pd; green, Ru. (E) Compositional line profiles of Pd and Ru for the RuPd NPs
recorded along the arrow shown in the STEM image (D).
ACS Paragon Plus Environment
8

Page 9 of 26
ACS Catalysis
1
2
3
4
5
6
7
8
9
The XRD patterns of various samples are shown in Figure 3. All samples present a broadened
peak centered at 43.2°, which could be assigned to the CN support. Diffraction peaks of Pd/CN
at 2θ of 40.1°, 46.7° and 68.1° are indexed to the (111), (200) and (220) crystal planes of Pd,
respectively. These peaks indicate that the deposited Pd of Pd/CN catalyst has a face-centered
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
3
4
cubic (fcc) structure. However, no characteristic peaks of Ru can be fitted in the XRD patterns
of Ru/CN, indicating that the Ru NPs are less than 4 nm in size and well dispersed on the support,
3
5
which is also in agreement with the HRTEM results (Figure S6). Moreover, no peaks
corresponding to Ru and Pd are detected in the RuPd/CN catalysts, which demonstrate that the
Ru and Pd form a RuPd alloy with very small particle size along with a good dispersion on the
support, which is also in accordance with the HRTEM results.
Figure 3. XRD patterns of different catalysts.
To get further insight into the interactions between Ru and Pd, XPS investigations were then
conducted (Figure 4). The binding energies are corrected with reference to the C 1s line at 284.5
ACS Paragon Plus Environment
9

ACS Catalysis
Page 10 of 26
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
eV. As shown in Figure 4 (A), an obvious positive shift (0.2~0.5 eV) in binding energy can be
observed for RuPd/CN with respect to Pd/CN, indicating a change in the electronic properties of
Pd caused by the alloying effect between Ru and Pd, which can be also certified by the binding
energy shift of Ru. As the Ru 3d3/2 peak overlaps with that of C 1s on support CN, Ru 3p peak
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
3
6, 37, 38
are employed for all samples to determine the chemical state of Ru.
Compared with
Ru/CN, the binding energy of Ru 3p3/2 for RuPd/CN presented a negative shift (0.2~0.3 eV) after
the formation of RuPd alloy.
For a more detailed understanding of the XPS measurements, Table 3 summarized the XPS-
derived ratios of oxidized and reduced metal states with different catalysts, giving evidence of
the surface Pd electronic state changes induced by the addition of Ru. It was found that, contrast
0
2+
to monometallic catalysts (Pd/CN and Ru/CN), the ratio of Pd /Pd decreased while the ratio of
0
n+
Ru /Ru increased for the bimetallic catalyst (RuPd/CN), confirming that the existence of Pd
n+
promoted the reduction of Ru . In conclusion, such shifts suggest that electronic status of Ru
and Pd modulated as a result of alloy formation, thereby influencing the catalytic behavior of Pd
in the hydrogenation reaction. This will be further confirmed by the catalyst evaluation results
described below.
H -TPR experiments are performed to further confirm the interaction between Ru and Pd
2
o
(
Figure 5). The Pd/CN presents a single large hydrogen release peak centered at 70 C, which is
caused by the decomposition of palladium hydride (PdH ), indicating the easy reducibility of
x
2+ 16, 31, 39
Pd .
However, the reduction profile of the Ru/CN catalyst shows two hydrogen
o
o
consumption peaks with maximum at about 78 C and 134 C, demonstrating two types of
4
0
ruthenium oxides might have been formed on the Ru/CN catalyst. For the bimetallic catalyst
RuPd/CN, only a weak and broad hydrogen consumption peak in the temperature ranges 60~117
ACS Paragon Plus Environment
1
0

Page 11 of 26
ACS Catalysis
1
2
3
4
5
6
7
8
9
o
C was observed, revealing that interaction occurred between Ru and Pd. We deduce that this
peak may be related to the reduction of Ru oxides. Thus, the existence of Pd metal helps the
reduction of ruthenium oxides, in agreement with the XPS analysis.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 4. XPS spectra of Pd 3d (A) and Ru 3p (B) in the different catalysts.
ACS Paragon Plus Environment
1
1

ACS Catalysis
Page 12 of 26
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
Table 3. Binding energies (eV) and curve fitting results of Pd 3d and Ru 3p XPS spectra.
Pd 3d5/2(eV)
Ru 3p3/2(eV)
Relative percentage (%)
Catalyst
2+
0
n+
0
0
2+
0
n+
Pd
337.6
337.8
-
Pd
Ru
Ru
-
Pd /Pd
Ru /Ru
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Pd/CN
RuPd/CN
Ru/CN
335.6
336.1
-
-
72/28
52/49
-
-
463.8
464.0
461.8
462.1
62/38
48/52
Figure 5. H -TPR patterns of CN supported Pd, Ru and RuPd catalysts.
2
Having proved the successfully preparation of RuPd/CN catalyst with Ru and Pd finely
alloyed together with small size, then the catalytic performance are tested in the hydrogenation
of BA to CCA. As shown in Table 4, under the given mild reaction conditions, both Ru/CN and
Pd/CN showed low BA conversion, whereas RuPd/CN exhibited a relatively high conversion of
6
7%. Indeed, this phenomenon results from the remarkably promotion effect of RuPd alloy
ACS Paragon Plus Environment
1
2

Page 13 of 26
ACS Catalysis
1
2
3
4
5
6
7
8
9
formation. We also prepared Ru^Pd/CN through an ultrasound-assisted two step reduction
method (see Supporting Information), which also presented a lower catalytic performance
compared with the co-reduction method prepared RuPd/CN (Table 4, entry 5), suggesting the
synergistic effect of Ru and Pd generated during the process of preparation. In consequence, the
highly efficient catalytic performance of RuPd/CN inspired us to perform the scale-up
experiment (Table 4, entry 4). In this typical process, BA can almost completely selective
hydrogenation to CCA within 2 hours, achieving a relatively high turn-over frequencies (TOFs)
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
-1
of 2066 h .
a
Table 4. BA Hydrogenation with different catalyst.
Conversion/% and
-1
b
Entry Catalyst
TOF (h )
Pd
(selectivity %)
1
2
3
Pd/CN
Ru/CN
38(100)
1.7
-
9(100)
RuPd/CN
RuPd/CN
Ru^Pd/CN
67(100)
11.5
2066
8.9
c
4
5
100(100)
52(100)
d
a
o
Reaction conditions: BA 0.5 mmol, catalyst 50 mg, solvent water 25 mL, 85 C, 0.1 MPa H , 6
2
b
c
hours. Obtained by assuming that the Pd atoms were solely responsible for the activity.
o
Reaction conditions: BA 10 mmol, catalyst 25 mg, solvent water 50 mL, 100 C, 5 MPa H , 2
2
d
hours. This catalyst was prepared by an ultrasound-assisted two step reduction method (see
Supporting Information).
ACS Paragon Plus Environment
1
3

ACS Catalysis
Page 14 of 26
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
The effects of hydrogen pressure on the activity of different catalysts were investigated as
shown in Figure 6 (A). Interestingly, the activity of RuPd/CN and Ru/CN both increased along
with the elevated pressure, while an activity platform of Ru/CN emerges at 0.8 MPa H pressure.
2
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Pd/CN shows the lowest activity to BA hydrogenation. The increase of H pressure has rare
2
impact on the activity of Pd/CN, since the earliest platform appeared at 0.4 MPa. In order to
further understand the platform phenomenon newly found, the adsorption energies of BA on Pd,
Ru and RuPd alloy are calculated respectively, hoping to obtain a preliminary explanation (The
relevant adsorption modes are shown in Figure S2). As is shown in Figure 6 (B), BA displays no
affinity to the Pd surface with small positive adsorption energy. This indicates the low
concentration of the chemisorbed BA and explains the resulted early platform on Pd/CN catalyst
since the Pd surface is mostly covered by dissociated H atoms. However, the chemisorption of
BA on the other two catalysts is rather favorable, with the adsorption energies of -0.7 eV and -
1
.29 eV for Ru and RuPd, respectively. The notable adsorption energies make a competitive
chemisorption between BA and H , thus the platform for Ru/CN catalyst appears later, and that
2
for RuPd/CN catalyst never shows the platform during the investigated H pressure range due to
2
the relatively large adsorption energy. Electronic structure was then performed to enlighten the
origin of different adsorption energies. Results showed that the electron transfer between BA and
the catalysts is quite relevant to the binding strength of BA on the catalysts (See Table S4 and the
related discussion for more details in the supporting information).
It is noteworthy that excessive large adsorption energy could lead to relatively lower activity
4
1
according to the Sabatier principle. The activities and adsorption energies for RuPd/CN and
Ru/CN seem to be self-contradictory, due to the fact that RuPd/CN possesses relatively larger
adsorption energy, while maintains a better activity than Ru/CN. In fact, the paradox is induced
ACS Paragon Plus Environment
1
4

Page 15 of 26
ACS Catalysis
1
2
3
4
5
6
7
8
9
by the different amount of active sites in different catalysts, which can be verified through XPS
0
n+
analysis (Table 3). Compared with Ru/CN, the increased Ru /Ru ratio in RuPd/CN occurred
after the formation of RuPd alloy, which may be conducive to the enhanced activity of RuPd/CN.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 6. (A) Influence of hydrogen pressure on BA conversion with different catalysts.
o
Reaction conditions: BA 1 mmol, catalyst 25 mg, solvent water 25 mL, 55 C, 1 h. (B) The
adsorption energies of BA on different catalysts derived from DFT calculations.
ACS Paragon Plus Environment
1
5

ACS Catalysis
Page 16 of 26
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
Figure 7. The optimized adsorption modes of BA in the water solvent on (A) Pd, (B) Ru and (C)
RuPd catalysts, respectively. Dark green: Pd, light green: Ru, grey: carbon, red: oxygen, and
white: hydrogen.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
6
42
Anderson and Bai proposed that the polar carboxyl group of BA is repulsive to the catalyst
and faces upward to the polar solvent, such as water. However, the calculation results performed
here provides a distinguishing insight. When excluding the solvent, the optimized structures of
the chemisorption of BA on the three catalysts, reflect that the C=O of the carboxyl group
(COOH) binds on the catalyst surface indeed apart from Pd (see Figure S2). Considering the
conducting experimental conditions, the adsorption modes of BA on the catalysts were
recalculated by introducing the effects of solvation (see Figure 7). The adsorption mode of BA
on Pd mostly remains the same, while it is not the case for Ru and RuPd catalysts. The hydrogen
(
H) atom in COOH dissolves into the solvent due to the ionization of water and the two oxygen
O) atoms in reserve both bind to the surfaces of the catalysts. It can be concluded that the
(
configuration of COOH in chemisorbed BA in water solvent is determined by both the nature of
the catalysts and the effects of the solvation, through the comparison of the BA adsorption modes
among the three catalysts. To be exact, the adsorption mode of the C=O fragment is in all
probability affected only by the nature of the catalysts rather than the effects of the solvation
since its configuration changes little in both vacuum and water solvent on each catalyst.
However, the adsorption mode of the OH fragment is likely influenced by both factors since the
H atom of COOH in vacuum dissolves into water solvent on Ru and RuPd while it remains on Pd
in both cases. Unfortunately, it is hard to get the adsorption energy of BA in water solvent due to
the numerous relative configurations among the water molecules. Therefore the charge transfer is
ACS Paragon Plus Environment
1
6

Page 17 of 26
ACS Catalysis
1
2
3
4
5
6
7
8
9
utilized as the chemisorption strength descriptor here, rather than the adsorption energy. As can
be seen in Table S4, the charge transfer of BA or the relevant acid ion changes only a little in
water solvent compared with that in vacuum. So it is rational to deduce that the trend of the
distinguishing adsorption energies of BA on different catalysts remains the same in water solvent.
This is why the adsorption energies of BA on the catalysts in vacuum are used to study the
platform.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
The excellent selectivity for BA hydrogenation on the three catalysts is obviously interesting.
In other words, the reason why the COOH group does not undergo the hydrogenation process is
of great important. Figure 7 probably can explain in part. In water solvent, the H atom in COOH
of BA which chemisorbed on Ru and RuPd catalysts respectively dissolves into water
spontaneously, which means COOH of BA more likely tends to release a H atom rather than
receive one. Furthermore, we calculated the thermodynamics of COOH dissociation and
hydrogenation respectively, in vacuum for simplicity. The energy results are shown in Table 5.
For Pd, the positive COOH hydrogenation and dissociation energies which mean endothermic
reactions, imply that COOH tends to maintain itself since the surface H atoms from dissociated
H molecules prefer to stay on the surface rather than bind to COOH and dissociation of COOH
2
is thermodynamically unfavourable under low temperatures. For Ru and RuPd, the positive
COOH hydrogenation and negative dissociation energies indicate that COOH
thermodynamically intends to dissociate the H atom resulting in two O atoms binding to the
catalyst surfaces. In conclusion, the hydrogenation of COOH is thermodynamically favorable in
none of the cases.
ACS Paragon Plus Environment
1
7

ACS Catalysis
Page 18 of 26
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
Table 5. The thermodynamics of hydrogenation and dissociation of COOH in BA. Negative
value means exdothermic reaction and positive value means the opposite. The relevant optimized
structures studied for COOH hydrogenation and dissociation can be seen in Figure S3.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Catalysts
Hydrogenation
Dissociation
Pd
0.36
0.65
Ru
0.79
-0.53
RuPd
0.20
-0.29
Gratifyingly, RuPd/CN also showed impressive activity in the hydrogenation of benzoic acid
derivatives (Table S6). In a final set of experiments, the reusability of RuPd/CN contrast with
commercial Pd/AC (Pd loading is 5 wt. %) was investigated (Figure 8). Results revealed that
after easy separation and pretreatment, RuPd/CN still could achieve a high conversion of 85%
after four batches, demonstrating its good deactivation resistance and recyclability. While for
commercial Pd/AC, there was a considerable decrease in catalytic activity during these recycling
tests. Furthermore, no traces of leached Ru or Pd species were detected in the reaction filtrate of
RuPd/CN as catalyst. These results demonstrated that the highly active RuPd/CN was more
stable than commercial Pd/AC under the investigated conditions. Its excellent catalytic
performance and good recyclability will make the RuPd/CN catalyst attractive for both
fundamental research and practical applications.
ACS Paragon Plus Environment
1
8

Page 19 of 26
ACS Catalysis
1
2
3
4
5
6
7
8
9
RuPd/CN
Pd/AC
1
00
80
60
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
4
2
0
0
0
1
2
3
4
Cycles
Figure 8. Comparison of the reusability of the RuPd/CN and commercial Pd/AC in the BA
hydrogenation under the same reaction conditions. Reaction conditions: BA 0.75 mmol, catalyst
o
50 mg, solvent water 25 mL, 55 C, 0.4 MPa H pressure, 1 h.
2
3
. CONCLUSIONS
Alloyed RuPd/CN catalyst was prepared via a simple ultrasound-assisted co-reduction
technique, exhibiting a remarkably superior activity and excellent stability over their
monometallic counterparts for the hydrogenation of BA under mild conditions. The excellent
0
n+
catalytic performance was mainly attributed to the increased Ru /Ru ratio induced by RuPd
formation confirmed by various characterizations. The platform on the activity to the H pressure
2
present different phenomenon on different catalysts was further explained by calculating the
adsorption energy of BA on the catalysts from a first-principle view. And the unique
phenomenon was due to the relatively strong adsorption energies of BA on the RuPd/CN. The
factors influencing the adsorption modes of BA, especially the configuration of the carboxyl
group are investigated preliminarily in first principle, giving a distinct view from the former
ACS Paragon Plus Environment
1
9

ACS Catalysis
Page 20 of 26
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
work. The reason why the carboxyl group in BA does not undergo hydrogenation, which results
in the superior selectivity (>99%), is also revealed by the comparisons of the thermodynamics of
hydrogenation and dissociation of the carboxyl group. In addition, the strategy reported here
provides a means for seeking more economical metal elements alloying with noble metal to
prepare bimetallic catalysts, which are applicable for various hydrogenation reactions, with
superior catalytic performance.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
4. EXPERIMENTAL SECTION
4
.1. Catalyst preparation
2
5
The N-doped carbon (CN) was synthesized as described previously. Bimetallic MPd/CN
(M=Ru, Cu, Fe, Ni and In) and RuM/CN (M=Cu, Fe, Ni and In) catalysts were prepared by
ultrasound-assisted co-reduction method. Taking the typical synthesis of RuPd/CN as an
example, appropriate amounts of CN was dispersed in deionized water in a beaker under
ultrasound, and then desired amount RuCl aqueous solution (0.01 g/mL) and Na PdCl aqueous
3
2
4
solution (0.01 g/mL) were added into the beaker under treatment in ultrasound for 10 minutes.
Then 10 mL freshly prepared NaBH aqueous solution (2 mg/mL) was added to the suspension
4
under ultrasound treatment for another 30 minutes. The solid were separated from the solution by
o
filtration and washed with water thoroughly. The obtained catalysts were dried at 70 C overnight,
and then it was treated with a simple grinding and denoted as RuPd/CN. Pd/CN and Ru/CN were
prepared using the same methodology for comparison.
4
.2. Catalyst characterization
The BET specific surface areas were measured on a surface area and porosity analyzer
Micromeritics, ASAP 2020 HD88). Actual content of Ru and Pd in the prepared catalysts were
(
ACS Paragon Plus Environment
2
0

Page 21 of 26
ACS Catalysis
1
2
3
4
5
6
7
8
9
measured by inductively coupled plasma-atomic emission spectroscopy (ICP-AES) on a Plasma-
Spec-II spectrometer. The dispersion of Pd was calculated on the basis of CO chemisorption at
room temperature, using a CHEMBET-3000 apparatus (Quantachrome Co.). High-resolution
transmission electron microscopy (HRTEM) was carried out on an FEI Tecnai G2 F20 S-TWIN
microscope. High-resolution scanning transmission electron microscopy (HRSTEM) high-angle
annular dark-field (HAADF)-STEM and EDX analyses were recorded on a Titan G280-200 w/
ChemiSTEM instrument. X-ray power diffraction analysis (XRD) was performed using Ultima
TV X-ray diffractometer with Cu Ka radiation (1.54 Å). The X-ray photoelectron spectra (XPS)
were obtained by an ESCALAB MARK II spherical analyzer using an aluminum-magnesium
binode (Al 1486.6 eV, Mg 1253.6 eV) X-ray source. Hydrogen temperature-programmed
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
reduction (H -TPR) was conducted in FINESORB-3010 apparatus equipped with a thermal
2
conductivity detector (TCD). Before a TPR run, catalysts were pretreated in Ar at 473 K for 2
hours. TPR was performed in a flow of 10% H /Ar mixture gas at a flow rate of 10 sccm with a
2
o
temperature ramp of 10 C /min.
4
.3. Hydrogenation of BA
In a typical process, 0.5 mmol BA and 50 mg RuPd/CN were put into a three-neck flask, and
2
5 mL deionized water was employed as a green solvent. The reaction was carried out at a
o
temperature of 85 C with magnetic stirring at a speed of 1000 rpm. Before reaction, a balloon
filled with hydrogen was connected to the flask to replace the air. After the reaction, the contents
of products and substrate were determined by GC-FID and the products were identified by GC-
MS.
4
.4. Computational setup
ACS Paragon Plus Environment
2
1

ACS Catalysis
Page 22 of 26
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
The calculations reported here are performed by using periodic, spin-polarized DFT as
4
3, 44
implemented in Vienna ab initio program package (VASP).
The electron-ion interactions are
4
5
described by the projector augmented wave (PAW) method proposed by Blöchl and
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
46
47
implemented by Kresse . RPBE functional is used as exchange-correlation functional
approximation and a plane wave basis set with an energy cutoff of 400 eV is used. Only gamma
point is used for the Brillouin zone sampling, during the structure optimization, while a kpoint of
4
8
3
*3*1 is used for bader charge analysis . A p (5×5) surpercell containing a four-layer slab with
100 atoms was modeled. The periodic condition is employed along the x and y direction. The
vacuum space along the z direction was set to be 13 Å. For RuPd catalyst, Pd was alloyed to the
sub-layer of Ru catalyst (Figure S1). The upper two layer atoms in the cell are allowed to relax
during the structure optimization and the bottom two layer atoms are fixed. When solvent, i.e.
water is considered, two water layers with 17 water molecules are introduced to simulate a
similar density of liquid water phase. The relaxation is stopped when the force residue on the
atom is smaller than 0.02 eV/Å. The adsorption energy for BA chemisorption is defined as:
Eads = E – E – EBA
tot
slab
Where E is the total energy after BA adsorption the on catalysts; Eslab is the energy of the
tot
clean catalyst alone; EBA is the energy of BA in the gas phase.
ASSOCIATED CONTENT
Supporting Information.
ACS Paragon Plus Environment
2
2

Page 23 of 26
ACS Catalysis
1
2
3
4
5
6
7
8
9
Experimental details, ICP-AES results, curve fitting of N adsorption-desorption isotherms,
2
HRTEM images of Ru/CN and Pd/CN catalysts, the effect of time and solvents on the catalysts
activity, the hydrogenation of benzoic acid derivaties in Supporting Information. This material is
available free of charge via the Internet at http://pubs.acs.org.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
AUTHOR INFORMATION
Corresponding Author
*
E-mail: chemwy@zju.edu.cn. Fax: +86-571-87951895.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENT
Financial support from the National Natural Science Foundation of China (21376208), the
Zhejiang Provincial Natural Science Foundation for Distinguished Young Scholars of China
(LR13B030001), the Specialized Research Fund for the Doctoral Program of Higher Education
(J20130060), the Fundamental Research Funds for the Central Universities, the Program for
Zhejiang Leading Team of S&T Innovation, the Partner Group Program of the Zhejiang
University and the Max-Planck Society are greatly appreciated.
REFERENCES
(1) Moore, B. S.; Cho, H.; Casati, R.; Kennedy, E.; Reynolds, K. A.; Mocek, U.; Beale, J. M.;
Floss, H. G., J. Am. Chem. Soc. 1993, 115, 5254-5266.
ACS Paragon Plus Environment
2
3

ACS Catalysis
Page 24 of 26
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
(
2) Temkin, M.; Konyukhov, V. Y.; Kul'kova, N., JOURNAL OF THE RESEARCH
INSTITUTE FOR CATALYSIS HOKKAIDO UNIVERSITY 1981, 28, 363-370.
3) Anderson, J.; McKenna, F.-M.; Linares-Solano, A.; Wells, R. K., Catal. Lett. 2007, 119,
6-20.
4) Gaude, D.; Le Goaller, R.; Luche, J.-L.; Pierre, J.-L., Tetrahedron Lett. 1984, 25, 5897-
5898.
(
1
(
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
(5) Wang, H.; Zhao, F., Int. J. Mol. Sci. 2007, 8, 628-634.
(6) Claus, P.; Berndt, H.; Mohr, C.; Radnik, J.; Shin, E.-J.; Keane, M. A., J. Catal. 2000, 192,
88-97.
(
(
(
(
7) Cervantes, G. G.; Aires, F. C. S.; Bertolini, J., J. Catal. 2003, 214, 26-32.
8) Cabiac, A.; Delahay, G.; Durand, R.; Trens, P.; Coq, B.; Plée, D., Carbon 2007, 45, 3-10.
9) Panpranot, J.; Kontapakdee, K.; Praserthdam, P., J. Phys. Chem. B, 2006, 110, 8019-8024.
10) Panpranot, J.; Pattamakomsan, K.; Goodwin Jr, J. G.; Praserthdam, P., Catal. Commun.
2
004, 5, 583-590.
(11) Wang, Y.; Yao, J.; Li, H.; Su, D.; Antonietti, M., J. Am. Chem. Soc. 2011, 133, 2362-2365.
(12) Ueno, T.; Suzuki, M.; Goto, T.; Matsumoto, T.; Nagayama, K.; Watanabe, Y., Angew.
Chem. 2004, 116, 2581-2584.
(13) Liu, H.; Jiang, T.; Han, B.; Liang, S.; Zhou, Y., Science 2009, 326, 1250-1252.
(14) Zhao, C.; Kou, Y.; Lemonidou, A. A.; Li, X.; Lercher, J. A., Angew. Chem. 2009, 121,
4
1
047-4050.
(15) Xu, X.; Li, Y.; Gong, Y.; Zhang, P.; Li, H.; Wang, Y., J. Am. Chem. Soc. 2012, 134,
6987-16990.
(
16) Anderson, J. A.; Athawale, A.; Imrie, F. E.; McKenna, F. M.; McCue, A.; Molyneux, D.;
Power, K.; Shand, M.; Wells, R. P. K., J. Catal. 2010, 270, 9-15.
17) Amadou, J.; Chizari, K.; Houllé, M.; Janowska, I.; Ersen, O.; Bégin, D.; Pham-Huu, C.,
(
Catal. Today 2008, 138, 62-68.
(18) Elꢀas, A. L.; Botello-Mꢁndez, A. s. R.; Meneses-Rodrꢀguez, D.; Jehovꢂ Gonzꢂlez, V.;
Ramꢀrez-Gonzꢂlez, D.; Ci, L.; Muꢃoz-Sandoval, E.; Ajayan, P. M.; Terrones, H.; Terrones, M.,
Nano Lett. 2009, 10, 366-372.
(
19) Zhang, P.; Yuan, J.; Fellinger, T.-P.; Antonietti, M.; Li, H.; Wang, Y., Angew. Chem., Int.
Ed. 2013, 52, 6028-6032.
20) Liu, R.; Mahurin, S. M.; Li, C.; Unocic, R. R.; Idrobo, J. C.; Gao, H.; Pennycook, S. J.;
Dai, S., Angew. Chem., Int. Ed. 2011, 50, 6799-6802.
(
(21) Yang, S.; Feng, X.; Wang, X.; Müllen, K., Angew. Chem., Int. Ed. 2011, 50, 5339-5343.
(22) Yang, W.; Fellinger, T.-P.; Antonietti, M., J. Am. Chem. Soc. 2010, 133, 206-209.
(23) Fulvio, P. F.; Lee, J. S.; Mayes, R. T.; Wang, X.; Mahurin, S. M.; Dai, S., Phys. Chem.
Chem. Phys. 2011, 13, 13486-13491.
24) Lee, J. S.; Wang, X.; Luo, H.; Baker, G. A.; Dai, S., J. Am. Chem. Soc. 2009, 131, 4596-
597.
(
4
(25) Xu, X.; Tang, M.; Li, M.; Li, H.; Wang, Y., ACS Catal. 2014, 4, 3132-3135.
(26) Yang, X.; Chen, D.; Liao, S.; Song, H.; Li, Y.; Fu, Z.; Su, Y., J. Catal. 2012, 291, 36-43.
ACS Paragon Plus Environment
2
4

Page 25 of 26
ACS Catalysis
1
2
3
4
5
6
7
8
9
(
27) Henning, A. M.; Watt, J.; Miedziak, P. J.; Cheong, S.; Santonastaso, M.; Song, M.;
Takeda, Y.; Kirkland, A. I.; Taylor, S. H.; Tilley, R. D., Angew. Chem., Int. Ed. 2013, 52, 1477-
1480.
(28) Hirasawa, S.; Watanabe, H.; Kizuka, T.; Nakagawa, Y.; Tomishige, K., J. Catal. 2013,
3
00, 205-216.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(29) Hermannsdörfer, J.; Friedrich, M.; Miyajima, N.; Albuquerque, R. Q.; Kümmel, S.;
Kempe, R., Angew. Chem., Int. Ed. 2012, 51, 11473-11477.
30) Vicente, A.; Lafaye, G.; Especel, C.; Marécot, P.; Williams, C. T., J. Catal. 2011, 283,
33-142.
31) Sun, J.; Karim, A. M.; Zhang, H.; Kovarik, L.; Li, X. S.; Hensley, A. J.; McEwen, J.-S.;
Wang, Y., J. Catal. 2013, 306, 47-57.
(
1
(
(32) Lee, J.; Kim, Y. T.; Huber, G. W., Green Chem. 2014, 16, 708-718.
(33) Jin, X.; Dang, L.; Lohrman, J.; Subramaniam, B.; Ren, S.; Chaudhari, R. V., ACS Nano
2
013, 7, 1309-1316.
34) Son, S. U.; Jang, Y.; Park, J.; Na, H. B.; Park, H. M.; Yun, H. J.; Lee, J.; Hyeon, T., J. Am.
Chem. Soc. 2004, 126, 5026-5027.
(
(35) Wang, C.; Li, B.; Lin, H.; Yuan, Y., J. Power Sources 2012, 202, 200-208.
(36) Luo, G.; Yan, S.; Qiao, M.; Zhuang, J.; Fan, K., Appl. Catal. A: Gen. 2004, 275, 95-102.
(37) Kusada, K.; Kobayashi, H.; Ikeda, R.; Kubota, Y.; Takata, M.; Toh, S.; Yamamoto, T.;
Matsumura, S.; Sumi, N.; Sato, K.; Nagaoka, K.; Kitagawa, H., J. Am. Chem. Soc. 2014, 136,
864-1871.
(38) Fang, M.; Machalaba, N.; Sanchez-Delgado, R. A., Dalton Transactions 2011, 40, 10621-
10632.
1
(39) Sá, J.; Arteaga, G. D.; Daley, R. A.; Bernardi, J.; Anderson, J. A., The J. Phys. Chem. B
2
006, 110, 17090-17095.
(40) da-Silva, J. W.; Cobo, A. J. G., Appl. Catal. A: Gen. 2003, 252, 9-16.
(41) Knözinger, H.; Kochloefl, K., Heterogeneous Catalysis and Solid Catalysts. In Ullmann's
Encyclopedia of Industrial Chemistry, Wiley-VCH Verlag GmbH & Co. KGaA: 2000.
(42) Bai, G.; Wen, X.; Zhao, Z.; Li, F.; Dong, H.; Qiu, M., Ind. Eng. Chem. Res. 2013, 52,
2
266-2272.
43) Kresse, G.; Furthmüller, J., Comp. Mater. Sci. 1996, 6, 15-50.
(44) Kresse, G.; Furthmüller, J., Phys. Rev. B 1996, 54, 11169.
(
(
(
(
(
45) Blöchl, P. E., Phys. Rev. B 1994, 50, 17953.
46) Kresse, G.; Joubert, D., Phys. Rev. B 1999, 59, 1758.
47) Hammer, B.; Hansen, L. B.; Nørskov, J. K., Phys. Rev. B 1999, 59, 7413.
48) Bader, R. F. W., Atoms in Molecules. In Encyclopedia of Computational Chemistry: John
Wiley & Sons, Ltd: 2002.
ACS Paragon Plus Environment
2
5

ACS Catalysis
Page 26 of 26
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
ACS Paragon Plus Environment
2
6