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Nano Res
1
Porous bimetallic Pt-Fe nanocatalysts for highly
efficient hydrogenation of acetone
Yongjun Ji†, Yuen Wu$ (), Guofeng Zhao†, Dingsheng Wang†, Lei Liu‡,§, Wei He‡,§ and Yadong Li†()
Nano Res., Just Accepted Manuscript • DOI 10.1007/s12274-015-0777-z
http://www.thenanoresearch.com on April 8, 2015
© Tsinghua University Press 2015
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Nano Research
DOI 10.1007/s12274-015-0777-z
Porous bimetallic Pt-Fe nanocatalysts for highly
efficient hydrogenation of acetone
Yongjun Ji,† Yuen Wu$ (), Guofeng Zhao†,
Dingsheng Wang†, Lei Liu‡,§, Wei He‡,§, and
Yadong Li†()
†Department of Chemistry, Tsinghua University, Beijing
100084, China
‡Tsinghua-Peking Center for Life Sciences, Tsinghua
University, Beijing 100084, China
§School of Medicine, Tsinghua University, Beijing
100084, China
$Center of Advanced Nanocatalysis (CAN-USTC) and
Department of Chemistry, University of Science and
Technology of China, Hefei, Anhui 230026, China
Porous Pt-Fe bimetallic nanocrystals were synthesized via
self-assembly which can effectively facilitate the manufacturing
of 2-propanol from acetone.
Porous bimetallic Pt-Fe nanocatalysts for highly
efficient hydrogenation of acetone
Yongjun Ji,† Yuen Wu$ (), Guofeng Zhao†, Dingsheng Wang†, Lei Liu‡,§, Wei He‡,§, and Yadong Li†()
†
‡
§
Received: day month year
Revised: day month year
Accepted: day month year
© Tsinghua University Press
and Springer-Verlag Berlin
Heidelberg 2014
KEYWORDS
Porous Pt-Fe NCs,
self-assembly,
Acetone hydrogenation,
highly active,
good stability,
interface effect
ABSTRACT
Porous Pt-Fe bimetallic nanocrystals were synthesized via self-assembly which
can effectively facilitate the manufacturing of 2-propanol from acetone. This
bimetallic catalyst owning three dimensional channels shows turnover
frequencies (TOFs) up to 972 h-1 for a continuous process more than 50 hours.
Preliminary mechanistic studies suggest that the high reactivity is strictly
related to the interface consist of bimetallic Pt-Fe alloy and the Fe2O3-x. The
understanding of real catalytic behavior and catalytic mechanism on model
systems help to fabricate more considerable Pt/Fe3O4 catalyst owning improved
activity and lifetime which endow the great potential in large-scale industrial
application.
Nano Research
DOI ()
Research Article
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2 Nano Res.
2-propanol is an important industrial chemical both
as intermediates and as high-value components for
the perfume industry [1]. On one hand, traditionally,
2-propanol has mainly been produced from
propylene via hydration, but this process is
energy-consuming and environmentally unfriendly
[2]. On the other hand, an urgent need is efficient
conversion of acetone, which is the main by-product
from manufacturing phenol in the so-called cumene
process [3], to other important chemicals because of
its surplus worldwide [4].Therefore, the catalytic
selective hydrogenation of acetone into 2-propanol is
an atom-economic reaction, which not only realized
the utilization of the waste but also become the key
joint of the circular economy (Scheme 1). Moreover,
this reaction is of great interest for applications in
chemical heat pumps or fuel cells, together with
storage of hydrogen regarding a future H2 economy
[5-8].
Numerous tremendeous research efforts have
been donated to develop practical and convenient
catalyst to effect this key reaction in the past decade
[9-14]. Nevertheless, most of these catalysts suffer
from the intrinsic low activity and/or selectivity due
to the formation of other products including methyl
isobutyl ketone (from the reaction of acetone
condensation, dehydration, and subsequent
hydrogenation) or diisopropyl ether from
condensation of two isopropyl alcohol molecules, as
well as some serious toxicity issues which required
cumbersome operation and harsh conditions. Even to
date, efficient hydrogenation of acetone catalyzed by
stable heterogeneous catalysts with considerable
catalytic lifetime are widely known technological
barriers for the industrial and environmental
concerns. Recently, one inspiring study by Finke and
co-workers show that costly Ir metal is effective
catalyst for selective hydrogenation of acetone. The
chloride-stabilized Ir(0) nanocluster catalyst, formed
in situ from commercial [(1,5-COD)IrCl] iridium
precursor, can activate acetone efficiently under
relatively mild Conditions [15]. This method,
however expedient, unfortunately generate a
stoichiometric amount of acid (for example, H+Cl-),
which is not environmentally friendly and thus
limiting its practical application for large-scale
industrial production.
Due to large surface area and high density of
surface edge/corner atoms which can effectively
reduce activation energy, porous metal structure such
have stimulated extensive research attention as a
outstanding catalysts for their diverse applications
[16-18]. Herein, we employ oriented attanchment
mechanism to successfully assemble a porous Pt-Fe
alloy nanocrystals (NCs) which exhibit highly porous
features and three dimensional channels. Serving a
excellent accessibility to the reactants species, this
unique nanostructure is demonstrated to show
considerable activity (turnover frequency (TOF) up
to 972 h-1) and selectivity (100% for
2-propanol)towards hydrogenation of acetone under
mild conditions. Applying this solid catalyst onto a
fixed-bed flow reactor, an incredible enhancement in
lifetime for continuous production of 2-propanol is
achieved in comparison to state-of-the-art catalysts
[14, 15].
Scheme 1 Structure diagram of circular economy
To prepare porous Pt-Fe alloy NCs, we employ
octadecylamine and oleylamine as solvent and
ligands to stabilize the monodispersed Pt-Fe colloids.
The synthesis is based on the co-reduction of
Pt(acac)2 and Fe(acac)3 (acac=acetylacetonate,
CH3COCHCOCH3) in the octadecylamine and
oleylamine systems at 260 oC under N2 protection (1
atm). In a typical synthesis, octadecylamine (5 g) was
firstly heated to 80 oC to form a warm solvent and
kept for 5 min. When the temperature was raised to
260 oC, a solution (2.5ml) of oleylamine containing
Pt(acac)2 (0.0472 g) and Fe(acac)3 (0.0424 g) was then
injected. The obtained turbid liquid was maintained
at this temperature under N2 protection for 10 min.
After the reaction mixture was cooled to 70 oC, the
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3 Nano Res.
30 40 50 60 70 80
*
** *
*
*
**
Fe3O
4
Fe
PtFe3
PtFe2
PtFe
Pt(3
11)
(220)
(200)
(111)
Inte
nsit
y (
a.u
.)
2Theta (degree)
product was washed by ethanol and cyclohexane for
three times and redispersed in cyclohexane for
further use.
Figure 1 (a) TEM, (b) HRTEM, (c) HAADF-STEM images of
porous PtFe NCs, as well as corresponding element maps and
(d) corresponding energy dispersive X-ray spectroscopy.
As shown in Figure 1a, the as-synthesized NCs
exhibit narrow size distribution (25±5 nm) and
uniform shape purity. High-resolution transmission
electron microscope (HRTEM) was used to image the
microstructure of porous Pt-Fe NCs. As shown in
Figure 1b, the Pt-Fe NCs surveyed exhibit a three
dimensional porous channels which is assembled by
small particles less than 5 nm. As the lattice spacing
of 0.22 nm is characteristic of [111] facets, the
assembly of subunits prior to orient along {111}
direction. The image displayed that the Pt-Fe NCs are
well separated with no agglomeration occurring. The
high-angle annular dark-field scanning transmission
electron microscope (HAADF-STEM) micrograph
(Figure 1c) displays the elemental mapping of a
typical PtFe NP. The compositional distribution for
both of Pt (red) and Fe (yellow) are uniform
throughout a whole particle, evidencing the alloyed
Pt-Fe phase obtained.
A series of samples were obtained from different
stages of the growth process to gain insight into the
formation of porous Pt-Fe alloy. As shown in Figure
S1, abundant Pt-Fe small particles firstly emerged at
initial stage when the Pt-Fe nucleus reached the
critical concentration. The force originated from high
ratio of volume to surface area of small particles
drive them into attachment and coalescence, which
result in some larger particles. As the reaction
proceeding with a prolonged time, the isolated small
particles will disappear gradually, leaving a porous
nanoparticle. The growth process of this unique
porous structure is accord with the oriented
attachment mechanism [19]. As shown in Figure 1b
and Figure S2 in the Electronic Supplementary
Material (ESM), the HRTEM image indicates the
porous Pt-Fe NCs are obviously polycrystalline
nature with high dense cores, which is not perfectly
followed the oriented attachment that the adjacent
particles prior to share the same crystallographic
orientation. This imperfect oriented attachment can
be ascribed to explosive generation of a high
concentration of small particles in the initial stage,
leading to some small misorientation at the interface
which didn’t adopt the thermodynamic mode. The
structural evolution from small particles to porous
nanodendrites is illustrated in Figure S1e in the ESM.
Figure 2 XRD patterns of as-prepared Pt and Pt-Fe NCs.
Figure 2 shows the XRD patterns of all the
as-prepared Pt and Pt-Fe NCs. In the case of Pt NCs,
the characteristic reflections could be indexed to {111},
{200}, and {220} planes in the fcc Pt phase (JCPDS
4-802). Comparing with those of pure Pt sample
observed, the reflections of Pt-Fe NCs slightly shifted
to high angles when the content of Fe increases,
which could be arise from the decreased lattice
spacing caused by the alloying Fe and Pt. Addition of
more Fe(acac)3 promoted the separate nucleation of
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4 Nano Res.
80 75 70 65
Pt4f Pt04f5/2 Pt
04f7/2
cba
Inte
nsit
y (
a.u
.)
Binding Energy (eV)740 730 720 710 700
c
d
b
Fe2p Fe2+
or Fe3+
Fe0
Inte
nsit
y (
a.u
.)
Binding Energy (eV)
Fe components. Their composition could be
effectively adjusted via controlling the molar ratios of
the two precursors. If the metal precursor contained
excess of Fe(acac)3, a physical mixture of Pt-Fe and
phase-separated Fe3O4 NCs were observed,
confirmed by TEM image and the following XRD
pattern (marked by *), which was in agreement with
our previous study [20]. The Pt : Fe atomic ratios
were further determined by the energy dispersive
X-ray spectroscopy (EDS) (Figure 1d) and ICP-AES
(Table 1), which indicate that the composition of the
final products can be easily controlled by the ratios of
metal precursors.
The X-ray photoelectron spectroscopy (XPS) was
used to investigate the chemical states of Pt and Fe in
the Pt, PtFe and PtFe2 and PtFe3 NCs samples (Figure
3). The high-resolution XPS spectra show that the
binding energies of Pt 4f7/2 and Pt 4f5/2, peaks are
located at 71.3 and 74.6 eV, respectively, which are
characteristic of Pt (0). Surprisingly, the signal
attributed to Fe 2p3/2 of Pt-Fe sample were
dominated by Fe (II) or Fe (Ⅲ), revealing most of the
Fe content on the surface were oxidized to form some
small oxide particles or clusters, in good agreement
with the published lirerature [21], probably due to
the treatment of drying at 80 oC in air overnight.
Figure 3 XPS spectra of Pt 4f and Fe 2p peaks of (a) Pt, (b) PtFe,
(c) PtFe2 and (d) PtFe3 NCs .
Taking high surface area of the porous nanoalloy
(45.5 m2/g) as an advantage, we employed these Pt-Fe
catalysts to effect acetone hydrogenation reaction. To
perform the catalytic tests, we first deposited the
Pt-Fe NPs on a high-surface-area activated carbon
support (800 m2/g) via sonication of the two
constituents (5 wt% Pt) in 10 mL of hexane, then
further being purified by centrifugation and dried.
Inspiringly, the main products of this reaction were
2-propanol (Scheme S1 in the ESM). The capping
surfactant on each NP was removed by annealing the
sample at 300 °C under mixed gases atmosphere of
nitrogen (30 mL min-1) and hydrogen (30 mL min-1)
for 2 h. As evidenced by IR spectra (Figure S3 in the
ESM), where the peaks of 2924 and 2853 cm-1
attributed to the anti-symmetric methyl stretch and
the symmetric methylene stretches became weakened
obviously. However, no significant change in particle
size and morphology was found after heat treatment,
as confirmed by the TEM images (as shown in Figure
1a). After effective removal of surfactant, more
surface atoms on the Pt-Fe NCs can emerge and serve
as chemically active sites.
Table 1 Catalytic activity and 2-propanol selectivity in the
gas-phase acetone hydrogenation on Pt and Pt-Fe NCs catalysts[a]
Catalyst Pt Pt : Fe[b] Temp. Acetone conv. 2-propanol
(wt %) (atomic ratio) (oC) (%) sel. (%)
Pt/C 5.0 - 100 6.6 100
PtFe/C 5.0 0.99 : 1 100 79.7 100
PtFe2/C 5.0 0.48 : 1 100 78 100
PtFe3/C 5.0 0.32 : 1 100 74.2 100
[a]Reaction conditions: cat., 0.2 g; pressure, 0.1 MPa; acetone
feed rate, 1.8 mL h-1; H2, 30 mL min-1; N2, 30 mL min-1; TOS = 1
h. The all catalysts were activated at 300 oC in hydrogen (30 mL
min-1) and nitrogen flow (30 mL min-1) for 2 h before the
reaction. [b]Obtained by ICP-AES.
The initial study was carried out at 100 oC. Table
1 summarizes the conversion of acetone and
selectivity of 2-proponal. As shown in Table 1,
2-propanol was the sole product in such catalytic
conditions, and there was no by-products such as
methyl isobutyl ketone (from the reaction of acetone
condensation, dehydration, and subsequent
hydrogenation), or diisopropyl ether from
condensation of two isopropyl alcohol molecules
detected. However, the previously reported less
active catalytic systems typically lead to the mixture
of these chemicals under the comparable
experimental conditions [22, 23]. Reaction catalyzed
by the Pt/C catalyst (5 wt%) which was prepared by
using the same method but without addition of
Fe(acac)3 are included as comparison (Figure S4 in the
ESM). Only 6.6% acetone conversion was achieved
within 1 h time on stream (TOS), which is consistent
with the previous report [12]. However, the catalytic
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5 Nano Res.
40 80 120 160 2000
20
40
60
80
A
b
a
Aceto
ne c
on
v. (%
)
Temperature (oC)
0 10 20 30 40 50
0
20
40
60
80
B
b
a
Aceto
ne c
on
v. (%
)
Time on stream (h)
activity for the case of PtFe/C was enhanced
significantly under identical reaction conditions. A
remarkably improved acetone conversion (up to
79.7%) was achieved with 100% selectivity to
2-propanol, indicating the Pt-Fe catalyst exhibit a
pronounced ability to active hydrogenate acetone. It
was also observed the conversion of acetone
decreased with an increase of Fe content, which was
caused by experimental error (both conversion and
selectivity was ±1%).
Various experiments were performed to
investigate the influence between temperature and
activity. Figure 4A shows the dependence of acetone
conversion on various temperatures in the range of
60-200 oC for the Pt/C and PtFe/C catalyst after 1 h of
operation. In the case catalyzed by Pt/C catalyst, the
hydrogenation reaction of acetone didn’t
demonstrate obvious improved activity with
increased reaction temperature. In contrast, the
conversion of acetone catalyzed by PtFe/C promote
significantly with elevated reaction temperature and
reached 92.3% at 200 oC, proving that the Pt-Fe
catalyst was intrinsically high active to this reaction
but the Pt-only catalyst was inert, whereas the
selectivity toward 2-propanol exhibited only a
marginal drop from 100% to 98.5%. Even at
temperature as low as 60 oC, the PtFe/C even show
relative high activity for hydrogenation of acetone,
further confirming the efficience of this porous
nanoalloy catalysts.
Figure 4 Dependence of acetone conversion (A) with various
temperature and (B) with time on stream on PtFe/C (a) and Pt/C
(b) catalysts. Reaction conditions: (A) temp. 60-200 oC; time, 1 h;
(B) temp. 150 oC; time, 1-50 h; others, see Table 1.
Lifetime is another important parameter which
should be taken into consideration for iudustrial
application. Thus, the long-term catalytic stability of
PtFe/C and Pt/C catalysts at 150 oC were further
investigated. As shown in Figure 4B, the Pt/C catalyst
exhibited considerable decay of activity during the
duration test, which is in accordance with the earlier
studies [14, 24]. On the other hand, the PtFe/C
catalyst showed barely constant acetone conversion
and 100% of 2-propanol selectivity over a period of
50 h TOS test. TEM analysis shows that there is a
slight morphology change and aggregation observed
for PtFe/C catalyst after 50 h duration test (Figure S5
in the ESM). The TOF was calculated to 972 h-1, which
was measured at a 20% acetone conversion level
obtained with 0.03 g of catalyst and not affected by
the varying PtFe loading, throughout the whole
reaction process, maintaining almost no decline
under 50 h continuous 2-propanol production
condition. Therefore, the PtFe/C showed its great
potential as a stable and robust catalyst in practical
application due to its minimal sintering or structural
modification, while keeping its extraordinary
activity.
The outstanding activity and durability of these
Pt-Fe NPs stimulate us to explore the intrinsic
reaction mechanism. As evidenced by above XPS
characterization results, the metallic Pt was clearly
seen on the Pt-Fe surface while the Fe species was
present in the form of Fe2+ or Fe3+ state. Moreover,
experimental investigation has verified that Pt-Fe
alloy is very active for the acetone hydrogenation.
Previously, numerous literatures have claimed the
metal-oxide interface is usually crucial to optimize
the catalytic performance [25-27]. We speculated that
the extraordinary reactivity may result from the
existence of the interfaces consist of bimetallic Pt-Fe
alloy and the Fe2O3-x, which have positive effect on
the activation of carbonyl group. It is reasonable to
anticipate the exposed Pt atoms serve as reactive
center to activate the dissociation of H2. Meanwhile,
the adsorption of carbonyl group took place at the
interface of Pt-Fe alloy and the Fe2O3-x, making
accessibility for acetone much more easily. Thus, the
Pt-Fe/Fe2O3-x composite catalysts may perfectly show
their synergistic effect that can both cleavage the H-H
bond and promote the adsorption of carbonyl group,
which indeed facilitate the hydrogenation of acetone.
Guided by these insights, we thus further prepared
supported Pt/Fe3O4 (5 wt% Pt) nanocatalyst to
confirm the interface effect. As shown in the TEM
image, Pt NPs were well anchored over the
Fe3O4 support and had a narrow distribution in
average diameter of 2 nm (shown by circle in Figure
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6 Nano Res.
S6 in the ESM). From the HRTEM image of
Pt/Fe3O4 (Figure S7 in the ESM), the inter-fringe
distances of the Fe3O4 particles were measured to be
0.25 nm, which was close to the lattice spacing of the
(311) planes of cubic Fe3O4. Interfaces between Pt and
Fe3O4 were seen clearly. The XRD pattern of the
prepared Pt/Fe3O4 catalyst matched well with that of
Fe3O4, whilst the diffraction signals for the
Pt NCs could not be observed clearly due to the small
particle size of the Pt nanoclusters (Figure S8 in the
ESM).
Table 2 Catalytic activity and 2-propanol selectivity in the
gas-phase acetone hydrogenation over Pt/Fe3O4 supported
catalysts[a]
Entry Catalyst Pt Temp. Acetone conv. 2-propanol
(wt %) (oC) (%) sel. (%)
1 Pt/Fe3O4 5.0 60 93.5 100
2 Pt/Fe3O4 5.0 100 87.9 100
3 Pt/Fe3O4 5.0 150 81.2 100
4 Pt/Fe3O4 5.0 200 77.8 99.1
5 Pt/SiO2 5.0 150 5 100
[a]Reaction conditions: cat., 0.2 g; pressure, 0.1 MPa; acetone
feed rate, 1.8 mL h-1; H2, 30 mL min-1; N2, 30 mL min-1; TOS = 1
h.
Acetone hydrogenation reactions were also
conducted by the Pt/Fe3O4 catalyst. The
corresponding activity and selectivity were
summarized in Table 2. The Pt/Fe3O4 catalyst shows a
very high activity with 93.5 % acetone conversion
and 100% 2-propanol selectivity at 60 oC in 1 h. It was
very interesting to note that the higher the reaction
temperature, the lower the activity. However, the
reason was unclear at present but will be addressed
in our future studies. Moreover, Pt with 2 nm particle
size was supported on SiO2 to exclude the
interference of size effect of Pt (Figure S9 in the ESM).
The extremely low acetone conversion (5%) was
obtained, despite of the 100% 2-propanol selectivity
achieved (Table 2). The specific surface area of
Pt/Fe3O4 catalyst (44.6 m2/g) was found to be very
close to that of Pt-Fe nanodendrite (45.5 m2/g).
H2-TPD characterization was performed to determine
the exposed Pt atoms. The lower desorption
temperature indicated that the activation of H2 on the
Pt/Fe3O4 surface has a lower barrier, while the larger
area of the desorption peak (by a factor of 2,
compared with that of Pt-Fe sample) for the Pt/Fe3O4
sample indicated the larger population of H
adspecies (Figure S10 in the ESM). Above
characterization results and the catalytic performance
catalyzed by Pt/Fe3O4 catalyst reveal the interface
between Pt and Fe3O4 play a key role in effecting
the hydrogenation reaction of acetone. It may be
anticipated that the Pt/Fe3O4 catalyst might be also
active for other compounds containing carbonyl
group, an area of great interest because such
hydrogenations are related to industrially important
processes [28]. As an classical example shown in
Scheme S2 in the ESM, hydrogenation of
cyclohexanone to cyclohexanol is an extremely
important building block in the polymer industry. As
expected, this Pt/Fe3O4 catalyst was also very active
and efficient for this reaction under mild conditions
(at 170 oC and atmospheric pressure), also confirming
the importance of oxide-metal interface in effecting
the carbonyl group (Table S1 in the ESM) .
In summary, we successfully construct porous
Pt-Fe alloy NCs via self-assembly, which show high
activity towards hydrogenation of acetone, in which
the TON approached up to 48600 with an
outstanding TOF of 972 h-1 with more than 50 h
lifetime under continuous process. The underlying
mechanism were studied to reveal the interfaces
between Pt-Fe alloy and the Fe2O3-x play a crucial role
in assuring their high catalytic activity and selectivity.
The design of nanocomposite catalyst compose of the
hybrid perimeter is expected to pave the way in
industrial application for continuous production of
2-propanol.
Acknowledgements
This work was supported by the State Key Project of
Fundamental Research for Nanoscience and
Nanotechnology (2011CB932401, 2011CBA00500),
National key Basic Research Program of China
(2012CB224802), and the National Natural Science
Foundation of China (Grant No. 21221062, 21171105,
21322107 and 21131004).
Electronic Supplementary Material: Supplementary
material (Experimental section and catalytic reaction)
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7 Nano Res.
is available in the online version of this article at
http://dx.doi.org/10.1007/s12274-***-****-* References
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Nano Res.
Electronic Supplementary Material
Porous bimetallic Pt-Fe nanocatalysts for highly
efficient hydrogenation of acetone
Yongjun Ji,† Yuen Wu$ (), Guofeng Zhao†, Dingsheng Wang†, Lei Liu‡,§, Wei He‡,§, and Yadong Li†()
†Department of Chemistry, Tsinghua University, Beijing 100084, China
‡Tsinghua-Peking Center for Life Sciences, Tsinghua University, Beijing 100084, China
§School of Medicine, Tsinghua University, Beijing 100084, China
$Center of Advanced Nanocatalysis (CAN-USTC) and Department of Chemistry, University of Science and
Technology of China, Hefei, Anhui 230026, China
Supporting information to DOI 10.1007/s12274-****-****-*
Experimental Section
Scheme S1 Main product in the hydrogenation of acetone
Scheme S2 Main product in the hydrogenation of cyclohexanone
Table S1 Catalytic activity and cyclohexanol selectivity in the gas-phase cyclohexanone hydrogenation over
Pt/Fe3O4 supported catalysts
Figure S1 TEM images showing the morphological evolution of porous Pt-Fe nanodendrites. The sample
was collected at different reaction time: a) 3 min; b) 5 min; c) 7 min; d) 10 min. e) Scheme
illustration of morphological evolution process.
Figure S2 HRTEM images of porous Pt-Fe nanodendrites.
Figure S3 IR spectra of PtFe/C ctalyst.
Figure S4 TEM image of porous Pt nanodendrites.
Figure S5 TEM image of PtFe/C catalyst after being used in the acetone hydrogenation reaction for 50 h.
Figure S6 TEM images of as-synthesized Pt/Fe3O4 catalyst.
Figure S7 HRTEM images of as-synthesized Pt/Fe3O4 catalyst.
Figure S8 XRD patterns of as-synthesized Pt/Fe3O4 catalyst.
Figure S9 TEM images of (a) Pt, and (b) Pt/SiO2 .
Figure S10 H2-TPD spectras of (a) PtFe/C, and (b) Pt/Fe3O4 catalysts.
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Experimental Section
Chemicals
The reagents used in this work, including octadecylamine, acetone, cyclohexanone, cyclohexane, FeCl2 •
4H2O, NaOH and EtOH were of analytical grade from the Beijing Chemical Factory of China, Pt(acac)2,
Fe(acac)3, H2PtCl6 and oleylamine were purchased from Alfa Aesar. All the reagents were used without further
purification.
Preparation of Pt/Fe3O4 catalyst
Into the three-necked bottle, 200 mL of water was first introduced under N2 atmosphere (1 atm). Then
heating it to 80 oC, 1 g of FeCl2 • 4H2O was added under vigorously stirring to form a homogenous solution,
when 0.5 g NaOH was introduced. Subsequently, 660 μL of 0.1 g/mL of H2PtCl6 solution was injected rapidly.
After stirring for 1 h, the product was purified by centrifugation. Finally, the resulting sample was dried at 60
oC overnight. After that, uniform Pt/Fe3O4 with maximized interfaces was obtained.
Preparation of Pt/SiO2 catalyst
Pt colloidal solution was synthesized following previously reported procedure,[1] a glycol solution of NaOH
(50 ml, 0.26 M) was added dropwise into a glycol solution of H2PtCl6·6H2O (50mL, 20 g/L) under stirring. The
mixture was stirred vigorously for 30 minutes and then heated at 160 oC by microwave for 5 min under
nitrogen atmosphere. A dark-brown Pt colloid (Pt: 3.7 g/L) was obtained.
12.2 ml of the prepared Pt colloid solution was added dropwise into a suspension containing 0.75 g of the
SiO2 support and 30 ml of ethanol under stirring. After stirring vigorously for an hour, the precipitate was
washed with water, and dried at 80 oC for one day to get the Pt/SiO2 (5.0 wt% Pt) catalyst as a black powder.
The catalytic reactions
Acetone and cyclohexanone hydrogenation reactions were all performed using a continuous flow system in a
fixed-bed quartz reactor (i.d. 7 mm) under atmospheric pressure using nitrogen as a carrier gas. The reactant
was fed into the reactor at a rate of 1.8 mL h-1. The typical catalyst loading, flow rate of nitrogen carrier, and
flow rate of hydrogen were 0.2 g, 30 mL min-1, and 30 mL min-1, respectively. The effluent products were
analyzed by an online gas chromatograph (SP-6890, flame ionization detector, FFAP capillary column). It
should be noted that the Pt and Pt-Fe alloy catalysts were activated at 300 oC in mixed gases of nitrogen flow
(30 mL min-1) and hydrogen flow (30 mL min-1) for 2 h before the reactions.
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Characterization
Before submitted to any characterizations, all the samples were dried at 80 oC in air overnight. X-ray
diffraction (XRD) patterns were recorded on a Rigaku RU-200b X-ray diffractometer with Cu Kα radiation (λ=
1.5418 Å ). The size and morphology of catalysts were analyzed on a Hitachi H-800 transmission electron
microscope (TEM) and a FEI Tecnai G2 F20 S-Twin high-resolution transmission electron microscope (HRTEM)
operating at an accelerating voltage of 200 kV. The samples were ground, dispersed in ethanol and deposited
on the copper grids prior to observation. The composition of the product was quantified by inductively
coupled plasma atomic emission spectroscopy (ICP-AES) and energy dispersive spectrometer (EDS). The EDS
was performed using SEM mode. X-ray photoelectron spectroscopy (XPS) experiments were performed on a
ULVAC PHI Quantera microprobe. Binding energies (BE) were calibrated by setting the measured BE of C 1s to
284.8 eV. N2 adsorption was carried out at 77 K on a BELSORP-MAX instrument after outgassing the samples
for 2 h under vacuum at 300 oC. Temperature-programmed desorption of hydrogen (H2-TPD) was conducted
on a Micromeritics tp-5080 equipment equipped with a thermal conductivity detector (TCD). The reduced
samples were first purged with He (50 mL min-1) for 30 min and then adsorption of H2 at room temperature.
After adsorption for 30 min, the system was purged with He for another 30 min, and the TPD test was
conducted in flowing He (50 mL/min) with a ramping rate of 15 °C/min.
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Nano Res.
OCat.
H2
OH
O
Cat.
H2
OH
Scheme S1 Main product in the hydrogenation of acetone
Scheme S2 Main product in the hydrogenation of cyclohexanone
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Table S1 Catalytic activity and cyclohexanol selectivity in the gas-phase cyclohexanone hydrogenation over
Pt/Fe3O4 supported catalysts[a]
Entry Catalyst Pt Temp. Cyclohexanone conv. Cyclohexanol sel.
(wt %) (oC) (%) (%)
1 Pt/Fe3O4 5.0 170 73.7 100
2 Pt/Fe3O4 5.0 200 72.1 100
3 Pt/Fe3O4 5 .0 220 70.5 100
4 Pt/Fe3O4 5.0 250 65.8 97.6
[a]Reaction conditions: cat., 0.2 g; pressure, 0.1 MPa; cyclohexanone feed rate, 1.8 mL h-1; H2, 30 mL min-1; N2, 30
mL min-1; TOS = 1 h.
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.
Figure S1 TEM images showing the morphological evolution of porous Pt-Fe nanodendrites. The sample was
collected at different reaction time: a) 3 min; b) 5 min; c) 7 min; d) 10 min. e) Scheme illustration of
morphological evolution process.
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Nano Res.
Figure S2 HRTEM images of porous Pt-Fe nanodendrites.
Figure S3 IR spectra of PtFe/C ctalyst.
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Nano Res.
100 nm
Figure S4 TEM image of porous Pt nanodendrites.
Figure S5 TEM image of PtFe/C catalyst after being used in the acetone hydrogenation reaction for 50 h.
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Nano Res.
Figure S6 TEM image of as-synthesized Pt/Fe3O4 catalyst.
Figure S7 HRTEM images of as-synthesized Pt/Fe3O4 catalyst.
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Nano Res.
20 30 40 50 60 70 80
Fe3O
4
(440)
Fe3O
4
(511)Fe
3O
4
(422)
Pt
(111) Fe3O
4
(400)
Fe3O
4
(311)
Fe3O
4
(220)
Inte
nsit
y (
a.u
.)
2Theta (degree)
Figure S8 XRD pattern of as-synthesized Pt/Fe3O4 catalyst.
Figure S9 TEM images of (a) Pt, and (b) Pt/SiO2 .
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Nano Res.
150 300 450 600 750 900
b
aInte
nsity (
a.u
.)
Temperature (oC)
Figure S10 H2-TPD spectras of (a) PtFe/C, and (b) Pt/Fe3O4 catalysts.
Reference:
[1] Lian, C.; Liu, H. Q.; Xiao, C.; Yang, W.; Zhang, K.; Liu, Y.; Wang, Y. Solvent-free selective hydrogenation
of chloronitrobenzene to chloroaniline over a robust Pt/Fe3O4 catalyst. Chem. Commun. 2012, 48, 3124–3126.
Address correspondence to yuenwu@ustc.edu.cn; ydli@mail.tsinghua.edu.cn
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