Prominent hydrogenation catalysis of a PVP-stabilized Au34 superatom provided by doping a single Rh atom

Article abstract of DOI:10.1039/c8cc03123a

A single rhodium atom was precisely doped into a gold cluster Au₃₄ stabilized by poly(N-vinyl-2-pyrrolidone) (Au:PVP) as revealed by mass spectrometry. The Rh-atom-doped Au:PVP exhibited remarkable catalytic activity for hydrogenation reactions of olefins, which was much higher than that of recently reported Pd-atom-doped Au:PVP.

Full text of DOI:10.1039/c8cc03123a

View Article Online
View Journal
ChemComm
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: S. Hasegawa, S.
Takano, S. Yamazoe and T. Tsukuda, Chem. Commun., 2018, DOI: 10.1039/C8CC03123A.
This is an Accepted Manuscript, which has been through the
Volume 52 Number
1 4 January 2016 Pages 1–216
Royal Society of Chemistry peer review process and has been
accepted for publication.
ChemComm
Accepted Manuscripts are published online shortly after
Chemical Communications
www.rsc.org/chemcomm
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
author guidelines.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the ethical guidelines, outlined
in our author and reviewer resource centre, still apply. In no
event shall the Royal Society of Chemistry be held responsible
for any errors or omissions in this Accepted Manuscript or any
consequences arising from the use of any information it contains.
ISSN 1359-7345
COMMUNICATION
Marilyn M. Olmstead, Alan L. Balch, Josep M. Poblet, Luis Echegoyenet al.
Reactivity differences of Sc3N@C2n (2n 68 and 80). Synthesis of the
first methanofullerene derivatives of Sc N@D5h-C80
=
3
rsc.li/chemcomm

Please do not adjust margins
ChemComm
Page 1 of 5
View Article Online
DOI: 10.1039/C8CC03123A
Journal Name
COMMUNICATION
Prominent hydrogenation catalysis of PVP-stabilized Au34
superatom provided by doping a single Rh atom
Shingo Hasegawa,a Shinjiro Takano,a Seiji Yamazoe a,b,c,d and Tatsuya Tsukuda *a,b
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
www.rsc.org/
A single rhodium atom was precisely doped into a gold cluster hydrogenation of C=C bonds.
Au34 stabilized by poly(N-vinyl-2-pyrrolidone) (Au:PVP) as revealed
AuRh:PVP was prepared by a procedure similar to that for
by mass spectrometry. Rh-doped Au:PVP exhibited remarkable AuPd:PVP.18 An aqueous solution of HAuCl4 and RhCl3 with a
catalytic activity for hydrogenation reactions of olefins, which was molar ratio of 97:3 was homogeneously mixed with that of
much higher than that of recently reported Pd-doped Au:PVP.
NaBH4 in a microfluidic mixer19 in the presence of PVP at 273 K.
AuRh:PVP was obtained as a dark brown colloidal dispersion.
As references, Au:PVP and AuPd:PVP were prepared by the
reported procedure.18,19 UV-Vis spectra of pure and doped
Au:PVP showed no localized surface plasmon resonance (LSPR)
band (Fig. S1), indicating the absence of clusters with a
diameter larger than 2 nm. The average diameter of Au:PVP,
AuPd:PVP and AuRh:PVP was determined to be 1.2±0.2,
1.1±0.3 and 1.3±0.3 nm, respectively, by transmission electron
Gold clusters stabilized by poly(N-vinyl-2-pyrrolidone) (Au:PVP)
have provided an ideal platform for studying the correlation
between structure and catalysis.1,2 Au clusters smaller than 2
nm show excellent catalytic activity in aerobic oxidation
reactions due to the negative charge on Au atoms imposed by
PVP.3-5 The activity is further improved by introducing other
elements such as Ag6,7 and Pd8-10 owing to intracluster electron
transfer to Au. For example, the catalytic activity was
maximized by doping 10% and 30% of Ag6 and Pd10 into
Au:PVP, respectively.
On the other hand, previous experimental11,12 and
theoretical13-17 studies have demonstrated that even a single-
atom dopant could dramatically change the reactivity of Au
clusters. Recently, we successfully doped a single Pd atom into
Au:PVP by the co-reduction method and demonstrated that
AuPd:PVP thus synthesized was more reactive than undoped
Au:PVP for aerobic oxidation and catalyzed chemoselective
hydrogenation reactions of the C=C bonds.18 This finding
illustrates that single Pd atom doping not only enhances the
oxidation catalysis of Au clusters but also provides a new
catalytic ability for hydrogenation. To extend the scope of this
approach, we herein doped a single Rh atom into Au:PVP as
confirmed by mass spectrometry. Rh-atom-doped Au:PVP
(AuRh:PVP) exhibited much higher activity than AuPd:PVP for
Fig. 1 TEM images of (a) Au:PVP, (b) AuPd:PVP and (c) AuRh:PVP
with diameter distributions in the insets and (d) PXRD patterns
of Au:PVP (blue), AuPd:PVP (green) and AuRh:PVP (red).
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
Please do not adjust margins

Please do not adjust margins
ChemComm
Page 2 of 5
View Article Online
DOI: 10.1039/C8CC03123A
COMMUNICATION
Journal Name
motif have been proposed based on photoelectron
spectroscopy, electron diffraction, and DFT calculations.24-31
Interestingly, the doping modes of Rh and Pd into Au34
were different; a Rh atom was added to Au34 while a Pd atom
was replaced with an Au atom in Au34. The difference in the
doping mode between Rh and Pd was supported by the results
of Rh K- and Pd K-edge extended X-ray absorption fine
structure (EXAFS) analysis. Fourier transformed EXAFS spectra
are shown in Figure S4 and structural parameters obtained by
curve-fitting analysis are summarized in Table S2. The EXAFS
data at Rh K-edge could not be fitted well only by assuming the
Rh–Au bonds, whereas that at Pd K-edge could be fitted only
with the Pd–Au bonds. Reasonable fitting results were
obtained when we assumed coexistence of the Rh–O bonds
rather than the Rh–Cl bonds. The cationic state of Rh in
AuRh:PVP is supported by the Rh K-edge XANES spectrum (Fig.
S5). The formation of the Rh–O bond(s) is ascribed to oxidation
of AuRh:PVP in air. The absence of oxygen adducts in the mass
spectra is probably due to the reductive dissociation of the O
species during the MALDI process, since trans-2-[3-(4-tert-
butylphenyl)-2-methyl-2-propenylidene]malononitrile used as
a matrix is known to be an efficient electron donating
matrix.32,33 The coordination numbers (CNs) of the Rh–Au bond
(3.2±0.7) at Rh K-edge was significantly smaller than that of
the Pd–Au bond (7.3±0.8) at Pd K-edge. The small CN value of
the Rh–Au bond and partial oxidation of the Rh dopant
suggested the structure model for AuRh:PVP in which a Rh
atom is attached on the surface of Au34, while a Pd atom is
incorporated in the surface of Au34 in AuPd:PVP.18 Why was a
doped Rh atom exposed on the Au cluster surface? Schaak et
al. reported in the synthesis of Au-Rh alloy nanoparticles that
the reduction of HAuCl4 proceeds faster than that of RhCl3.34
This result suggests that the formation of an exposed Rh atom
in AuRh:PVP is ascribed to the kinetics of the cluster
formation: a Rh atom is attached onto the preformed Au34
cluster. In analysis of EXAFS data of AuRh:PVP and AuPd:PVP at
Au-L3 edge, we did not take Au–Rh and Au–Pd bonds into
consideration, because intracluster bonds are dominated by
the Au–Au bonds. We included the Au–Cl bonds in the EXAFS
analysis based on the mass spectral data (Fig. 2b). The CN
values of the Au–Au bonds of the three samples (4.3–4.5) are
consistent with the cluster sizes determined by mass
spectrometry. Based on these results, we propose that the
difference in the doping modes is attributed to whether the
dopant atoms participate in the valence electron count or not:
the Pd dopant contributes to the electron counting, whereas
the Rh dopant does not.
microscopy (TEM) (Fig. 1). This result indicates that the
heterometal can be doped while retaining the diameter of
Au:PVP. This conclusion was also supported by the fact that
the widths of the diffraction peaks corresponding to Au(111) in
powder X-ray diffraction (PXRD) patterns were comparable
(Fig. 1).
To evaluate the chemical compositions of bimetallic
clusters included in AuRh:PVP, matrix-assisted laser
desorption/ionization (MALDI) mass spectra were measured.
Fig. S2 compares the MALDI mass spectra of AuRh:PVP and
Au:PVP recorded under high laser fluence. Only a series of
AunRh1– appeared in the mass spectrum of AuRh:PVP (Fig. S2a),
–
whereas Aun were observed in the mass spectrum of Au:PVP
(
–
Fig. S2b). The absence of undoped Aun and overdoped
–
AunRhm (m ≥ 2) in the mass spectrum of AuRh:PVP revealed
that the population of undoped and overdoped Au clusters
was negligibly small and demonstrated that a single Rh atom
was successfully introduced into each Au cluster. Fig. 2a shows
an expanded view of the mass spectrum of AuRh:PVP in Fig.
–
S2a. Although this figure suggests that Au33Rh1 is a dominant
species in the sample, there is a possibility that the mass
spectrum is accompanied by laser-induced dissociation. Fig. 2b
is a typical mass spectrum recorded under minimal laser
fluence to minimize dissociation during the MALDI process. We
–
observed Au34Rh1Clm as the most abundant species: although
the mass peaks were not isotopically resolved (Fig. S3), the
average mass numbers of the experimentally observed peaks
agreed with those theoretically calculated within 0.1% at most
(
Table S1). Adsorption of Cl atoms originating from the
synthetic precursors has also been observed in Au:PVP20 and
AuPd:PVP.18 Based on this mass spectral data, we concluded
that Au34Rh1 was formed as the most dominant species in
AuRh:PVP. The composition is comparable to Au34 and Au33Pd1
dominant clusters contained in Au:PVP and AuPd:PVP,
respectively.18,20,21 Bare Au34 is a well-known magic numbered
Au cluster and its magic stability has been ascribed to the
closure of superatomic shells (1S)2(1P)6(1D)10(2S)2(1F)14.22,23
A
variety of structures for Au34 such as Au4@Au30 with chiral
Catalysis of AuRh:PVP for hydrogenation of C=C bonds was
studied by using 1-dodecene, styrene and cyclooctene as
model substrates. To understand the effect of single-atom
doping on the catalysis, it is important to compare the catalysis
under conditions in which the clusters do not decompose or
aggregate. Although our previous study illustrated great
improvement of the catalytic activity of AuPd:PVP over Au:PVP,
UV-Vis spectroscopy suggested the aggregation of clusters
during the reactions. To circumvent such problems, we added
an excess amount of PVP to the reaction solution: the ratio of
metal atoms to PVP monomer units was increased up to
1:1000. This simple treatment dramatically improved the
stability of clusters as shown in UV-Vis spectra after the
reactions (Fig. S6). The hydrogenation of 1-dodecene did not
Fig. 2 MALDI mass spectra of AuRh:PVP recorded under (a) high
and (b) minimal laser fluence. The most dominant Au34Rh1
clusters with and without Cl adducts are highlighted in (b).
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
ChemComm
Page 3 of 5
View Article Online
DOI: 10.1039/C8CC03123A
Journal Name
COMMUNICATION
affect the spectra (Fig. S6a), while that of styrene and
This research was financially supported by the Elements
cyclooctene induced a slight change due to harsher conditions Strategy Initiative for Catalysts & Batteries (ESICB) and by the
employed for the catalytic reactions (Figs. S6b and ). As “Nanotechnology Platform” (No. 12024046) from the Ministry
c
shown in Table 1, only the doped Au:PVP could catalyze the of Education, Culture, Sports, Science, and Technology (MEXT)
hydrogenation reactions under mild reaction conditions. of Japan and a Grant-in-Aid for Scientific Research (A) (Grant
Although the synergistic effect of Au and transition metals on No. 17H01182) from the Japan Society for the Promotion of
catalysis is well known,35-42 these results clearly indicated that Science (JSPS). The synchrotron radiation experiments were
doping of even a single atom of Rh or Pd dramatically changed performed under the approval of the Japan Synchrotron
the reactivity of a Au34 superatom and led to the emergence of Radiation Research Institute (JASRI) (Proposal Nos. 2017A0910,
hydrogenation catalysis. Moreover, AuRh:PVP exhibited much 2017B0910 and 2017B0918).
higher catalytic activity than that of AuPd:PVP in all cases.
These dopant effects on catalysis cannot be ascribed to the
Conflicts of interest
modulation of the electronic structures of Au clusters: X-ray
There are no conflicts to declare.
photoelectron spectroscopy (Fig. S7) shows that the electronic
state of Au was not affected by the doping of Rh and Pd atoms
Notes and references
as we expected from the small doping amount. The Pd and Rh
1
2
3
4
5
H. Tsunoyama, H. Sakurai, Y. Negishi and T. Tsukuda, J. Am.
Chem. Soc., 2005, 127, 9374.
S. Yamazoe, K. Koyasu and T. Tsukuda, Acc. Chem. Res., 2014,
47, 816.
M. Okumura, Y. Kitagawa, T. Kawakami and M. Haruta,
Chem. Phys. Lett., 2008, 459, 133.
H. Tsunoyama, N. Ichikuni, H. Sakurai and T. Tsukuda, J. Am.
Chem. Soc., 2009, 131, 7086.
dopants act as active sites for hydrogenation and the
remarkable enhancement of hydrogenation catalysis by Rh
doping as compared to Pd doping is probably related to the
lower coordination state of the Rh dopant. We will study the
reaction mechanism in more detail including a possibility that
leached species are involved (boomerang mechanism).43,44
Table
1
Hydrogenation reactions catalyzed by Au:PVP,
S. Haesuwannakij, T. Kimura, Y. Furutani, K. Okumura, K.
Kokubo, T. Sakata, H. Yasuda, Y. Yakiyama and H. Sakurai, Sci.
Rep., 2017, 7, 9579.
AuPd:PVP and AuRh:PVP
6
7
8
9
N. K. Chaki, H. Tsunoyama, Y. Negishi, H. Sakurai and T.
Tsukuda, J. Phys. Chem. C, 2007, 111, 4885.
H. Zhang, M. Okumura and N. Toshima, J. Phys. Chem. C,
2011, 115, 14883.
S. S. Yudha, R. N. Dhital and H. Sakurai, Tetrahedron Lett.,
2011, 52, 2633.
S. Nishimura, Y. Yakita, M. Katayama, K. Higashimine and K.
Ebitani, Catal. Sci. Technol., 2013, 3, 351.
10 N. Hayashi, Y. Sakai, H. Tsunoyama and A. Nakajima,
Langmuir, 2014, 30, 10539.
11 H. Häkkinen, S. Abbet, A. Sanchez, U. Heiz and U. Landman,
Angew. Chem. Int. Ed., 2003, 42, 1297.
12 S. Xie, H. Tsunoyama, W. Kurashige, Y. Negishi and T.
Reaction Dopant H2 (MPa) Conversion (%) Selectivity(2a:3a)
-
<1
10
90
1
33
95
<1
2
-
33:67
75:25
(a)
(b)
(c)
Pd
Rh
-
Pd
Rh
-
0.1
0.25
0.5
-
-
-
-
-
-
Tsukuda, ACS Catal., 2012,
13 M. Walter and H. Häkkinen, Phys. Chem. Chem. Phys., 2006,
, 5407.
2, 1519.
8
14 N. K. Jena, K. R. S. Chandrakumar and S. K. Ghosh, J. Phys.
Chem. C, 2009, 113, 17885.
15 N. K. Jena, K. R. S. Chandrakumar and S. K. Ghosh, J. Phys.
Chem. Lett., 2011, 2, 1476.
16 B. H. Morrow, D. E. Resasco and A. Striolo, J. Phys. Chem. C,
2011, 115, 5637.
Pd
Rh
83
Reaction conditions: substrate 50 μmol; catalyst 2 at%; PVP 111
mg; ethanol 5mL; 303 K; 1h.
17 D. Manzoor, S. Krishnamurty and S. Pal, J. Phys. Chem. C,
2016, 120, 19636.
18 S. Hayashi, R. Ishida, S. Hasegawa, S. Yamazoe and T.
Tsukuda, Top. Catal., 2018, 61, 136.
19 H. Tsunoyama, N. Ichikuni and T. Tsukuda, Langmuir, 2008,
24, 11327.
20 R. Ishida, S. Arii, W. Kurashige, S. Yamazoe, K. Koyasu, Y.
Negishi and T. Tsukuda, Chin. J. Catal., 2016, 37, 1656.
In summary, we succeeded in doping a single Rh atom into
Au:PVP with atomic precision. MALDI mass spectrometry
revealed the selective doping of a single Rh atom to a Au34
superatom. Rh K-edge EXAFS analysis suggested that a Rh
atom is exposed on the surface of Au34, which was attributed
to reduction kinetics of Au and Rh precursor ions. AuRh:PVP
showed much higher catalytic activity in the hydrogenation of
olefins than AuPd:PVP without degradation of clusters. The
much higher activity was ascribed to the lower coordination
state of a Rh atom. Investigations for further insight about the
origin of high catalytic activity and extension of substrate
scope will be carried out in future work.
21 H. Tsunoyama and T. Tsukuda, J. Am. Chem. Soc., 2009, 131
18216.
,
22 I. Katakuse, T. Ichihara, Y. Fujita, T. Matsuo, T. Sakurai and H.
Matsuda, Int. J. Mass Spectrom. Ion Processes, 1985, 67, 229.
23 K. J. Taylor, C. L. Pettiette-Hall, O. Cheshnovsky and R. E.
Smalley, J. Chem. Phys., 1992, 96, 3319.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
ChemComm
Page 4 of 5
View Article Online
DOI: 10.1039/C8CC03123A
COMMUNICATION
Journal Name
24 A. Lechtken, D. Schooss, J. R. Stairs, M. N. Blom, F. Furche, N.
Morgner, O. Kostko, B. von Issendorff and M. M. Kappes,
Angew. Chem. Int. Ed., 2007, 46, 2944.
25 X. Gu, S. Bulusu, X. Li, X. C. Zheng, J. Li, X. G. Gong and L. S.
Wang, J. Phys. Chem. C, 2007, 111, 8228.
26 I. E. Santizo, F. Hidalgo, L. A. Pérez, C. Noguez and I. L.
Garzón, J. Phys. Chem. C, 2008, 112, 17533.
27 A. Vargas, G. Santarossa, M. Iannuzzi and A. Baiker, Phys.
Rev. B, 2009, 80, 195421.
28 N. Shao, W. Huang, Y. Gao, L. M. Wang, X. Li, L. S. Wang and
X. C. Zeng, J. Am. Chem. Soc., 2010, 132, 6596.
29 L. M. Wang and L. S. Wang, Nanoscale, 2012, 4, 4038.
30 L. X. Zhao, M. Zhang, H. Y. Zhang, X. J. Feng and Y. H. Luo, J.
Phys. Chem. A, 2015, 119, 11922.
31 S. Chiriki, S. Jindal and S. S. Bulusu, J. Chem. Phys. 2017, 146
084314.
,
32 L. Ulmer, J. Matty, H. G. Torres-Garcia and H. Luftmann, Eur.
J. Mass Spectrom., 2000, , 49.
6
33 A. Dass, A. Stevenson, G. R. Dubay, J. B. Tracy and R. W.
Murray, J. Am. Chem. Soc., 2008, 130, 5940.
34 E. R. Essinger-Hileman, D. DeCicco, J. F. Bondi and R. E.
Schaak, J. Mater. Chem., 2011, 21, 11599.
35 N. Toshima and T. Yonezawa, New J. Chem., 1998, 22, 1179.
36 D. I. Enache, J. K. Edwards, P. Landon, B. Solsona-Espriu, A. F.
Carley, A. A. Herzing, M. Watanabe, C. J. Kiely, D. W. Knight
and G. J. Hutchings, Science, 2006, 311, 362.
37 T. Balcha, J. R. Strobl, C. Fowler, P. Dash and R. W. J. Scott,
ACS Catal., 2011, 1, 425.
38 H. Zhang, T. Watanabe, M. Okumura, M. Haruta and N.
Toshima, Nat. Mater., 2012, 11, 49.
39 R. N. Dhital, C. Kamonsatikul, E. Somsook, K. Bobuatong, M.
Ehara, S. Karanjit and H. Sakurai, J. Am. Chem. Soc., 2012,
134, 20250.
40 L. Zhang, A. Wang, J. T. Miller, X. Liu, X. Yang, W. Wang, L. Li,
Y. Huang, C. Y. Mou and T. Zhang, ACS Catal., 2014, 4, 1546.
41 W. Luo, M. Sankar, A. M. Beale, Q. He, C. J. Kiely, P. C. A.
Bruijnincx and B. M. Weckhuysen, Nat. Commun., 2015, 6,
6540.
42 H. Miura, K. Endo, R. Ogawa and T. Shishido, ACS Catal.,
2017, , 1543.
7
43 S. Wittmann, A. Schätz, R. N. Grass, W. J. Stark and O. Reiser,
Angew. Chem. Int. Ed., 2010, 49, 1867.
44 A. Ohtaka, E. Sakaguchi, T. Yamaguchi, G. Hamasaka, Y.
Uozumi, O. Shimomura and R. Nomura, ChemCatChem,
2013, 5, 2167.
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 5 of 5
ChemComm