Porous bimetallic Pt-Fe nanocatalysts for highly efficient ... · PDF filePorous bimetallic...

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



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.



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

| www.editorialmanager.com/nare/default.asp

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

www.theNanoResearch.com∣www.Springer.com/journal/12274 | Nano Research

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


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


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


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)


7 Nano Res.

is available in the online version of this article at

http://dx.doi.org/10.1007/s12274-***-****-* References

[1] Anderson, L. C.; MacNaughton, N. W. The mechanism of

the catalytic reduction of some carbonyl compounds. J. Am.

Chem. Soc. 1942, 64, 1456–1459.

[2] Haining, G. J. Olefin hydration process and catalyst. U.S.

Patent 5,684,216 A, 1997.

[3] Niwa, S. I.; Eswaramoorthy, M.; Nair, J.; Raj, A.; Itoh, N.;

Shoji, H.; Namba, T.; Mizukami, F. One-step conversion of

benzene to phenol with a palladium membrane. Science

2002, 295, 105–107.

[4] Sheldon, R. A.; van Santen, R. A. Catalytic Oxidation,

Principles and Applications. World Scientific: Singapore,

1995.

[5] Gandia, L. M.; Montes, M. Effect of the design variables on

the energy performance and size parameters of a heat

transformer based on the system acetone/H2/2-propanol. Int.

J. Energy Res. 1992, 16, 851–864.

[6] Meng, N.; Shinoda, S.; Saito, Y. Improvements on thermal

efficiency of chemical heat pump involving the reaction

couple of 2-propanol dehydrogenation and acetone

hydrogenation. Int. J. Hydrogen Energy 1997, 22, 361–367.

[7] Pardillos-Guindet, J.; Vidal, S.; Court, J.; Fouilloux, P.

Electrode potential of a dispersed Raney nickel electrode

during acetone hydrogenation: influence of the solution and

reaction kinetics. J. Catal. 1995, 155, 12–20.

[8] Dresselhaus, M. Basic Research Needs For the Hydrogen

Economy: Report of the Basic Energy Sciences Workshop

on Hydrogen Production, Storage and Use. Office of

Science, U.S. Department of Energy: Washington, 2003.

[9] Lemcoff, N. O. Liquid phase catalytic hydrogenation of

acetone. J. Catal. 1977, 46, 356–364.

[10] Gandia, L. M.; Diaz, A.; Montes, M. Selectivity in the

high-temperature hydrogenation of acetone with

silica-supported nickel and cobalt catalysts. J. Catal. 1995,

157, 461–471.

[11] Sen, B.; Vannice, M. A. Metal-support effects on acetone

hydrogenation over platinum catalysts. J. Catal. 1988, 113,

52–71.

[12] Fuente, A. M.; Pulgar, G.; González, F.; Pesquera, C.;

Blanco,C. Activated carbon supported Pt catalysts: effect of

support texture and metal precursor on activity of acetone

hydrogenation. Appl. Catal. A 2001, 208, 35–46.

[13] Noyori, R.; Hashiguchi, S. Asymmetric transfer

hydrogenation catalyzed by chiral ruthenium complexes.

Acc. Chem. Res. 1997, 30, 97–102.

[14] Rao, R. S.; Walters, A. B.; Vannice, M. A. Influence of

crystallite size on acetone hydrogenation over copper

catalysts. J. Phys. Chem. B 2005, 109, 2086–2092.

[15] Özkar, S.; Finke, R. G. Iridium(0) nanocluster, acid-assisted

catalysis of neat acetone hydrogenation at room

temperature: exceptional activity, catalyst lifetime, and

selectivity at complete conversion. J. Am. Chem. Soc. 2005,

127, 4800–4808.

[16] (a) Niu, Z. Q.; Wang, D. S.; Yu, R.; Peng, Q.; Li, Y. D.

Highly branched Pt-Ni nanocrystals enclosed by stepped

surface for methanol oxidation. Chem. Sci. 2012, 3,

1925–1929. (b) Huang, X. Q.; Li, Y. J.; Chen, Y.; Zhou, E.

B.; Xu, Y. X.; Zhou, H. L.; Duan, X. F.; Huang, Y.

Palladium-based nanostructures with highly porous features

and perpendicular pore channels as enhanced organic

catalysts. Angew. Chem. Int. Ed. 2013, 52, 2520–2524.

[17] Wu, H. X.; Wang, P.; He, H. L.; Jin, Y. D. Controlled

synthesis of porous Ag/Au bimetallic hollow nanoshells

with tunable plasmonic and catalytic properties. Nano Res.

2012, 5, 135–144.

[18] Wang, L. J.; Zhang, K.; Hu, Z.; Duan, W. C.; Cheng, F. Y.;

Chen, J. Porous CuO nanowires as the anode of

rechargeable Na-ion batteries. Nano Res. 2014, 7, 199–208.

[19] Banfield, J. F.; Welch, S. A.; Zhang, H.; Ebert, T. T.; Penn, R.

L. Aggregation-based crystal growth and microstructure

development in natural iron oxyhydroxide

biomineralization products. Science 2000, 289, 751–754.

[20] Wang, D. S.; Peng, Q.; Li, Y. D. Nanocrystalline

intermetallics and alloys. Nano Res. 2010, 3, 574–580.

[21] Wang, H. L.; Krier, J. M.; Zhu, Z. W.; Melaet, G.; Wang, Y.

H.; Kennedy, G.; Alayoglu, S.; An, K.; Somorjai, G. A.

Promotion of hydrogenation of organic molecules by

incorporating iron into platinum nanoparticle catalysts:

displacement of inactive reaction intermediates. ACS Catal.

2013, 3, 2371–2375.

[22] Staude, E.; Patat, F. The Chemistry of the Ether Linkage.

Wiley: New York, 1967; pp 22–46.

[23] Narayanan, S.; Unnikrishnan, R. Selective hydrogenation of

acetone to methyl isobutyl ketone (MIBK) over

co-precipitated Ni/Al2O3 catalysts. Appl. Catal. A 1996,

145, 231–236.

[24] Cunningham, J.; Al-Sayyed, G. H.; Cronin, J. A.; Healy, C.;

Hirschwald, W. Surface synergisms between copper and its

oxides in catalytic isopropanol/acetone interconversions at

430-523 K. Appl. Catal. 1986, 25, 129–138.

[25] Boffa, A.; Lin, C.; Bell, A. T.; Somorjai, G. A. Promotion of

CO and CO2 hydrogenation over Rh by metal oxides: the

influence of oxide Lewis acidity and reducibility. J. Catal.

1994, 149, 149–158.

[26] Zhou, H. P.; Wu, H. S.; Shen, J.; Yin, A. X.; Sun, L. D.; Yan,

C. H. Thermally stable Pt/CeO2 hetero-nanocomposites

with high catalytic activity. J. Am. Chem. Soc. 2010, 132,

4998–4999.

[27] Bowker, M.; James, D.; Stone, P.; Bennett, R.; Perkins, N.;

Millard, L.; Greaves, J.; Dickinson, A. Catalysis at the

metal-support interface: exemplified by the photocatalytic

reforming of methanol on Pd/TiO2. J. Catal. 2003, 217,

427–433.

[28] Collman, J. P.; Hegedus, L. S.; Norton, J. R.; Finke, R. G.

Principles and Applications of Organotransition Metal

Chemistry, University Science Books, Mill Valley, CA,

1987, 619–665.

http://dx.doi.org/10.1007/s12274-***-****-*


Nano Res.

Electronic Supplementary Material



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.


Nano Res.

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.


Nano Res.

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.


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


Nano Res.

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.


Nano Res.

.

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.


Nano Res.

Figure S2 HRTEM images of porous Pt-Fe nanodendrites.

Figure S3 IR spectra of PtFe/C ctalyst.


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.


Nano Res.

Figure S6 TEM image of as-synthesized Pt/Fe3O4 catalyst.

Figure S7 HRTEM images of as-synthesized Pt/Fe3O4 catalyst.


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 .


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 [email protected]; [email protected]

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