Bimetallic Nickel-Iridium and Nickel-Osmium Alloy Nanoparticles and Their Catalytic Performance in Hydrogenation Reactions

Article abstract of DOI:10.1002/cctc.201700168

Bimetallic NiIr₄ and NiOs₄ alloy nanoparticles are prepared and studied with regard to their performance in catalytic hydrogenation reactions. NiIr₄ and NiOs₄ nanoparticles are obtained by oleylamine-driven reduction and exhibit mean diameters of (8.9±1.3) and (6.8±1.4) nm at low agglomeration. The phase composition was determined in detail by using different methods, which include high-resolution TEM, scanning transmission electron microscopy, selected-area electron diffraction, X-ray diffraction, and energy-dispersive X-ray spectroscopy. This and results in a uniform distribution of both metals Ni-Ir and Ni-Os with a ratio of 1:4. The catalytic performance of the NiIr₄ and NiOs₄ nanoparticles for hydrogenation reactions is evaluated using three selected model substrates: 1-octene, cinnamaldehyde, and diphenylacetylene. Similar sized Ni, Ir, and Os nanoparticles were used as references. Most remarkable are the excellent selectivity of NiOs₄ in the hydrogenation of cinnamaldehyde and the promising formation of (Z)-stilbene in terms of conversion activity and selectivity. The alloying of Ir and Os with Ni, moreover, is highly cost efficient. In general, both bimetallic alloy nanoparticles, NiIr₄ and NiOs₄, are shown here for the first time in terms of synthesis, composition, and catalytic hydrogenation.

Full text of DOI:10.1002/cctc.201700168

Accepted Article
Title: Bimetallic NiIr4 and NiOs4 Alloy Nanoparticles and Their
Catalytic Performance in Hydrogenation Reactions
Authors: Claus Feldmann, Alexander Egeberg, Christine Dietrich
Dietrich, Christian Kind, Radian Popescu, Dagmar Gerthsen,
and Silke Behrens
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: ChemCatChem 10.1002/cctc.201700168
Link to VoR: http://dx.doi.org/10.1002/cctc.201700168
A Journal of
www.chemcatchem.org

ChemCatChem
10.1002/cctc.201700168
Bimetallic NiIr and NiOs Alloy Nanoparticles and Their
4
4
Catalytic Performance in Hydrogenation Reactions
[
a]
[b]
[a]
[c]
Alexander Egeberg , Christine Dietrich , Christian Kind ,Radian Popescu , Dagmar
[
c]
[b]
[a]
Gerthsen , Silke Behrens and Claus Feldmann *
[
9]
Abstract. Bimetallic NiIr
prepared and studied regarding their performance in catalytic
hydrogenation reactions. NiIr and NiOs nanoparticles are
4
and NiOs
4
alloy nanoparticles are
catalytic water splitting
or via catalytic hydrazine
as well as for catalytic hydrogen
[12]
[
10]
decomposition,
oxidation reactions
[
11]
4
4
and ring-opening reactions.
obtained via oleylamine-driven reduction and exhibit mean
diameters of 8.9±1.3 and 6.8±1.4 nm at low agglomeration.
The phase composition was determined in detail based on
different methods including HRTEM, STEM, SAED, XRD and
EDXS and results in a uniform distribution of both metals Ni-Ir
and Ni-Os, with a ratio of 1:4. The catalytic performance of
Catalytic hydrogenation with Ni-Ir nanoparticles was yet
reported once based on heavily agglomerated
nanoparticles that nevertheless already indicate
[13]
promising conversion rates.
Moreover, pure Ir
nanoparticles supported on graphene were employed to
effectively catalyze the hydrogenation of benzene to
4 4
the NiIr and NiOs nanoparticles for hydrogenation reactions
[
14]
cyclohexane. Data regarding the catalytic activity of the
bimetallic Ni-Os system, to the best of our knowledge, are
not available by now. This lack of knowledge motivated
us to address the synthesis and characterization of
uniform bimetallic Ni-Ir and Ni-Os nanoparticles.
is evaluated using three selected model substrates: 1-octene,
cinnamaldehyde and diphenylacetylene. Similar sized Ni, Ir,
and Os nanoparticles serve as references. Most remarkable
4
are the excellent selectivity of NiOs in the hydrogenation of
cinnamaldehyde as well as the promising formation of Z-
stilbene in terms of conversion activity and selectivity.
Alloying Ir and Os with Ni, moreover, is highly cost efficient.
Besides
chemical
synthesis
and
structural
characterization, the as-prepared bimetallic Ni-Ir and Ni-
Os nanostructures were evaluated in view of the catalytic
hydrogenation including efficiency and selectivity based
on three model substrates. Thus, 1-octene was selected
due its low sterical hindrance and simple chemical
structure. The second example, cinnamaldehyde, is a
cornerstone of catalysis in terms of chemoselectivity
since the hydrogenation of α,β-unsaturated aldehydes is
particularly challenging due to the high thermodynamic
stability of the C=O bond in comparison to the allylic C=C
bond. The selective hydrogenation of such allylic
aldehydes to unsaturated alcohols, moreover, is
commercially [1r5e] levant in view of flavors and
In general, both bimetallic alloy nanoparticles – NiIr
4
and
NiOs – are here first shown in view of synthesis, composition
4
and catalytic hydrogenation.
Introduction
Bimetallic nanoparticles already turned out as highly
[1]
promising for high efficiency and selectivity in catalysis.
Specific examples, for instance, comprise the systems
[2]
Fe-Ru for efficient Fischer-Tropsch synthesis, Al-Fe as
[
3]
Pd-free hydrogenation catalyst, Rh-Pd for selective CO
[
4]
[5]
oxidation, Pt-Co for renewable fuel generation, or the
[6]
activation of gold in bimetallic systems. Several studies
have also demonstrated that bimetallic nanoparticles can
outperform their monometallic counterparts.
pharmaceutics.
Finally, diphenylacetylene is highly
relevant for production of (Z)-/(E)-stilbene, which is an
important building block for dyes, liquid crystals,
fluorescent whitners, and OLEDs. Usually, synthesis is
performed by Wittig or Heck reactions that essentially
consume stoichiometric amounts of organic reagents,
[
2-7]
Specific
intermetallic interactions in these alloyed or core-shell
type systems were postulated to result in synergistic
effects. This can include a tuned electronic or geometric
structure as well as an improved thermal or chemical
stability. As a result, bimetallic nanocatalysts did not only
display the combined properties of the pure components
[
16]
such as base. For all three test substrates – 1-octene,
cinnamaldehyde – the realization of novel atom-efficient
and selective heterogeneous catalyst is highly relevant.
but rather exhibit
performance in terms of activity, selectivity, etc.
a
significantly higher catalytic
[2-7]
In
Results and Discussion
some cases, the catalytic performance could be improved
even if one of the constituents was less active or even
inactive for certain reaction.
Material synthesis
4 4
The novel bimetallic NiIr and NiOs nanoparticles
Most of the yet available multimetallic nanocatalysts
[1-7]
were prepared in oleylamine that served as solvent,
surface stabilizing agent for controlling particle nucleation
and particle growth as well as reducing agent for the
reduction of the starting materials to the elemental
are based on precious metals.
To this concern,
alloying precious metals with an abundant, less-precious
metal is of particular interest not only for improving the
[
8]
catalytic properties but also for effective cost reduction.
metals. Thus, NiCl
OsCl ×nH O were used the starting materials and heated
to 300 °C. During heating, the change from light green
for Ni-Ir) and reddish-brown (for Ni-Os) solution to dark
brown suspensions indicated the successful reduction
and nucleation of NiOs and NiIr nanoparticles.
2
×6H
2
O
and IrCl
3
×nH
2
O
or
In contrast to bimetallic M-Pd or M-Pt systems (M: metal),
bimetallic systems of iridium and osmium have been
barely addressed, in general. Specifically, the system Ni-
Ir was yet described for hydrogen generation via electro-
3
2
(
_
_
[
[
[
a]
b]
c]
MSci. A. Egeberg, Dr. C. Kind, Prof. Dr. C. Feldmann
4
4
Institut für Anorganische Chemie, Karlsruhe Institute of
Technology (KIT), Engesserstr. 15, D-76131 Karlsruhe
After natural cooling to room temperature, the as-
prepared bimetallic nanoparticles were purified by
repeated centrifugation/redispersion from/in a mixture of
hexane and ethyl acetate (ratio 1:3). This measure,
especially, intends to separate the removal of oleylamine.
Finally, the metal nanoparticles can be easily redispersed
in hexane. The synthesis essentially requires the absence
of air/oxygen and moisture to avoid any oxidation.
Therefore, the synthesis was performed in dried argon
(Germany)
MSci. C. Dietrich, Priv.-Doz. Dr. Silke Behrens
Institut für Katalyseforschung und -technologie (IKFT), Karlsruhe
Institute of Technology (KIT)Postfach 3640, D-76021 Eggenstein-
Leopoldshafen (Germany)
Dr. R. Popescu, Prof. Dr. D. Gerthsen
Laboratorium für Elektronenmikroskopie, Karlsruhe Institute of
Technology (KIT), Engesserstr. 7, D-76131 Karlsruhe.
Supporting
information
(characterization
methods
and
synthesis/characterization of reference materials) for this article is
available on the WWW under http://dx.doi.org/xxxxx/anie.xxxxxx.
4 4
atmosphere. It is to be noted that NiOs and NiIr
This article is protected by copyright. All rights reserved.

ChemCatChem
10.1002/cctc.201700168
nanoparticles turned out as stable in air at room
the lattice as compared to bulk-Ir. It is to be noticed that
diffraction peaks of elemental Ir and/or Ni were not
observed in XRD and SAED patterns, suggesting the
presence of a pure binary Ni-Ir alloy phase.
temperature subsequent to synthesis.
Interestingly, the compositions NiIr
4
4
and NiOs were
obtained even if the ratio of the starting materials was
different from 1:4, which points to a specific stability of the
1
:4 phases at the conditions of synthesis. Thus, NiIr
NiOs are obviously most insoluble upon reducing
NiCl ×6H O, IrCl ×nH O and OsCl ×nH O in oleylamine.
4
and
4
2
2
3
2
3
2
As alloys, their formation can hardly be attributed to a
certain stability of the 1:4 compositions. In contrast, a
complex equilibrium between the stability of the
coordination complexes in solution (i.e. coordination of
2
+
3+
3+
Ni , Ir , Os by oleylamine) and the reduction potential
2
+
3+
3+
of the metals (i.e. reduction of Ni , Ir , Os
oleylamine) is involved. To this concern, it is to be noted
that neither IrCl ×nH O nor OsCl ×nH O can be reduced
by oleylamine in the absence of NiCl ×6H O. Thus, the
by
3
2
3
2
2
2
decisive equilibria – including the stability of the dissolved
coordination complexes and the redox potential for the
formation of elemental metals – have opposing trends
resulting in NiIr
with the here applied conditions of synthesis.
The reference materials pure Ni, Ir and Os
nanoparticles – were intended to exhibit almost identical
particle diameters as the as-prepared bimetallic NiOs
and NiIr . To this regard, pure Ni was prepared via a
4 4
and NiOs as the most stable phases
–
4
4
similar synthesis route. Pure Ir and Os were not available
from oleylamine-based synthesis due to the formation of
soluble coordination complexes. Thus, the Ir and Os
nanoparticles were obtained via a modified synthesis
protocol (see experimental section) with similar size and
colloidal stability as NiOs and NiIr (see Table 1; SI:
4 4
Figures S1-S4), and – subsequent to washing – similar
surface conditioning (see experimental section).
NiIr
4
nanoparticles
Subsequent to synthesis, the particle size and size
distribution of the as-prepared NiIr nanoparticles were
4
characterized by dynamic light scattering (DLS) and
electron microscopy. According to DLS, the as-prepared
NiIr
an average hydrodynamic diameter of 10.2±1.3 nm
Figure 1a,b). Low-energy scanning transmission electron
4
nanoparticles show a lognormal size distribution with
(
microscopy (STEM) overview images support this finding
based on a statistical evaluation of 100 nanoparticles with
a mean diameter of 8.9±1.3 nm (Figure 1c).
4
Figure 1. NiIr nanoparticles: a) Size distribution according to DLS; b)
photo of suspension in hexane; c) low-energy STEM overview image;
d) indexed XRD pattern (symbols) with whole-pattern-diffraction fit
Information regarding structure and composition of
the as-prepared NiIr
diffraction (XRD), selective area electron diffraction
SAED) and high-resolution transmission electron
4
nanoparticles was obtained by X-ray
(solid line) and difference plot; e) indexed SAED pattern of
nanoparticle ensemble; f) indexed radial scan (symbols) with whole-
pattern fit (solid lines) and difference plot, calculated from the SAED
pattern in (e); g) HRTEM image of typical Ni-Ir nanoparticle with
multiply twinned structure; h) HRTEM image of monocrystalline Ni-Ir
nanoparticle; i) diffractogram of the nanoparticle part marked by
dashed frame in (h) and calculated diffraction pattern with Miller
indices for the fcc structure (blue circles).
(
microscopy (HRTEM). Thus, the XRD pattern, together
with the corresponding fit and difference plot only show
two Bragg peaks that could be detected due to the limited
angular aperture of the applied detector (Figure 1d).
These peaks are attributed to
a single-phase Ni-Ir
Whereas the average structure of a quasi-infinite
number of particles and of particle aggregates were
derived via XRD and SAED, HRTEM allows studying the
structure of individual Ni-Ir nanoparticles. Accordingly,
lattice fringes extend through the whole nanoparticle and
indicate most often monocrystalline structures (Figure 1h)
accompanied by few multiply twinned structures
intermetallic alloy with face-centered-cubic (fcc)
a
structure (space group Fm-3m). This assessment is
supported by the fcc structure of both bulk-Ni and bulk-Ir
as well as by the formation of Ni-Ir intermetallic alloys with
fcc structure over the whole compositional range. The
here calculated lattice parameter (a = 0.374±0.004 nm) is
[
17]
3% smaller than for bulk-Ir (a = 0.384 nm) and for the Ir-
(
Figure 1g). Monocrystallinity is demonstrated by the
reference nanoparticles [ (a = 0.384±0.001). Moreover,
18]
good agreement between its 2-dimensional Fourier
transformation (denoted in the following as diffractogram)
and the calculated fcc-type diffraction pattern
XRD line-profile analysis
results in a mean crystallite
diameter of 9 nm, which is in good agreement with DLS
and STEM. All observed Debye-Scherrer rings on SAED
patterns of the nanoparticles can again be attributed to a
single-phase Ni-Ir alloy with fcc structure (Figure 1e).
From the corresponding azimuthally averaged intensity of
the SAED pattern (Figure 1f), a lattice parameter of
a = 0.373±0.003 nm was obtained. This finding is in good
agreement with XRD and supports a 3% contraction of
(
a = 0.371 nm, [111] zone-axis orientation) (Figure 1i). A
multiply twinned nanoparticle with several, rather small
facets and slightly different orientation is shown in
1
Figure 1g. Here, lattice-fringe distances of d = 0.22±0.01,
d
2
= 0.13±0.01, = 0.13±0.01 and = 0.19±0.01 nm
d
3
d
4
were measured on different facets of the Ni-Ir
nanoparticle that correspond to the (111), (220) and (200)
This article is protected by copyright. All rights reserved.

ChemCatChem
10.1002/cctc.201700168
[18]
lattice-plane distances (d(111) = 0.214,
d
(220) = 0.131,
was calculated by single XRD line-profile analysis,
which is well in agreement with DLS and STEM.
d(200) = 0.186 nm). Again, for both – monocrystalline and
twinned nanoparticles
–
the lattice parameters
from the nanoparticle
diffractogram are 3% smaller than the corresponding
SAED patterns confirm the XRD results (Figure 3f).
All observed Debye-Scherrer rings are in accordance with
the sole presence of a Ni-Os alloy with hcp structure. The
azimuthally averaged SAED pattern as well as the
corresponding whole-pattern fit and the difference plot
(
a = 0.371 nm)
derived
[
17]
value of bulk-Ir.
EDXS area scans were used to determine the
average chemical composition of the Ni-Ir nanoparticles
(Figure 3f,g)
result
in
lattice
parameters
of
(
Figure 2a,b) and show the characteristic lines of Ni-K
a = 0.261±0.003 and c = 0.423±0.004 nm that confirm the
hcp structure and the contracted lattice parameters (5%
in a and 2% in c). We also note that Bragg reflections of
elemental Ni and/or Os are not observed in the XRD and
SAED patterns.
and Ir-L series (lines of Cu-K series stem from the grid).
The quantification of the Ni and Ir content within the Ni-Ir
nanoparticle in Figure 2a yielded 20±2 at-% Ni and
8
0±1 at-% Ir. Furthermore, an average chemical
composition of Ni21±2Ir79±3 was obtained from EDXS area
scans of 60 Ni-Ir nanoparticles located in different regions
on the sample. Moreover, EDXS line-profiles indicate a
uniform Ni and Ir distribution and again an average
composition of 19±2 at-% Ni and 81±2 at-% Ir
(
Figure 2c,d). Finally, powder samples were pressed to
pellets and studied via EDXS (see SI). Again, a 1:4 ratio
of Ni and Ir was detected (SI: Table S1) and, in sum,
confirms the composition and homogeneity of NiIr
individual nanoparticles as well as for powder samples.
In conclusion, single-phase Ni-Ir alloy nanoparticles
with fcc structure and uniform chemical composition NiIr
4
for
4
were obtained as indicated by the above independent
analytical tools (XRD, SAED, HRTEM, EDXS). The
formation of
a single-phase Ni-Ir intermetallic alloy
rationalizes the contraction of the fcc lattice parameter of
the nanoparticles. A decrease of the lattice parameter
value is indeed expected after dissolving Ni
[19]
(rNi = 0.124 nm) in the structure of Ir (rIr = 0.136 nm).
Figure 2. NiIr
4
nanoparticles: a) HAADF-STEM image
with b) area-EDX spectrum (dashed box area in (a)); c)
HAADF STEM image with d) Ni and Ir composition
profiles (along orange line in (c)).
4
Figure 3. NiOs nanoparticles: a) Size distribution according to DLS;
b) photo of suspension in hexane; c,d) low-energy STEM and TEM
overview images; e) indexed XRD pattern (symbols) with whole-
pattern-diffraction fit (solid line) and difference plot; f) indexed SAED
pattern of nanoparticle ensemble; g) indexed radial scan (symbols)
with whole-pattern fit (solid lines) and difference plot, calculated from
SAED pattern in (f); h) typical HRTEM image; i) experimental
diffractogram of nanoparticle in (h) with calculated diffraction pattern
and Miller indices for hcp structure (blue circles). For legibility reasons,
not every reflection is marked and explicitly indexed in the
diffractogram. The indices of all other reflections can be calculated
from the low-indexed reflections. The white circle indicates the zero-
order beam (ZB).
Ni-Os nanoparticles
According to DLS, the as-prepared NiOs
nanoparticles exhibit narrow log-normal particle
distribution with an average hydrodynamic diameter of
.2±1.2 nm (Figure 3a,b). Low-energy STEM and TEM
overview images indicate a mean particle diameter of
.8±1.4 nm (based on a statistical evaluation of 100
nanoparticles, Figure 3c,d). According to XRD, the Ni-Os
nanoparticles adopt hexagonal-close-packed (hcp)
structure (space group P6 /mmc) with lattice parameters
4
a
8
6
Size, shape and structure of the as-prepared Ni-Os
nanoparticles were further studied in detail by HRTEM
analysis (Figure 3h). Lattice fringes extend through the
whole nanoparticle and indicate its crystallinity.
Diffractogram and calculated diffraction pattern are in
a
3
of a = 0.260±0.003 and c = 0.427±0.004 nm (Figure 3e,f).
Thus, a contraction of 5% (for a) and 2% (for c) was
observed in comparison to bulk-Os (a = 0.274,
c = 0.432 nm). An average crystallite diameter of 7 nm
very good agreement with a hcp structure (P6
a = 0.259, c = 0.419 nm, along the [211] zone axis, Figure
i). Again the lattice parameters a and c are contracted
3
/mmc,
3
This article is protected by copyright. All rights reserved.

ChemCatChem
10.1002/cctc.201700168
by 5 and 3%, respectively, in comparison to bulk-Os,
supporting the XRD and SAED results.
EDXS area scans reveal the characteristic X-ray lines
of the Ni-K and Os-L series (lines of Cu-K series stem
from the grid) (Figure 4a,b). Quantification of the Ni and
Os content of the nanoparticle in Figure 4a resulted in
Table 1. Mean diameter of the as-prepared NiIr
nanoparticles as well as of the Ni, Ir, and Os reference nanoparticles
according to DLS and TEM analysis).
4
and NiOs
4
(
Nanoparticles
Mean diameter (DLS)
[nm]
Mean diameter (TEM)
[nm]
NiIr
NiOs
Ni
Ir
Os
4
10.2±1.3
8.2±1.2
10.4±1.4
5.1±0.6
5.2±0.5
8.9±1.3
6.8±1.4
8.7±0.9
3.7±0.9
3.9±1.4
4
20±2 at-% Ni and 80±2 at-% Os. An average chemical
composition of Ni19±2Os81±3 was derived from EDXS area
scans of 110 Ni-Os nanoparticles from different regions of
the sample. Moreover, Ni- and Os-concentration profiles
from EDXS line scans show a uniform distribution of both
metals (Figure 4c,d) across the selected Ni-Os
nanoparticle as well as a similar composition (21±2 at-%
Ni, 79±2 at-% Os) as obtained from the area scans.
Finally, powder samples were pressed to pellets and
studied via EDXS (see SI), again resulting in a 1:4 ratio of
Ni and Os (SI: Table S1). Accordingly, any segregation of
elemental Ni and/or Os can be excluded.
Catalytic hydrogenation with NiIr
4 4
and NiOs particles
For further evaluation of the alloyed bimetallic NiIr
4
and NiOs nanoparticles, we tested the catalytic activity
4
and selectivity in hydrogenation reactions for three
unsaturated substrates (i.e., 1-octene, cinnamaldehyde
and diphenylacetylene). For all catalytic experiments, the
as-prepared
nanoparticles
were
employed
as
suspensions in hexane (1.5-3.0 mL). Although the partial
formation of agglomerates cannot be completely
excluded, the atoms located at the particle surface should
be, in principle, accessible to interact with the substrates.
Hence, turnover frequencies based on surface atoms
Similar to the Ni-Ir alloy nanoparticles, the Ni-Os
nanoparticles can be considered as single-phase alloy
nanoparticles with a uniform chemical composition of
4
NiOs . Structure and composition are reliably determined
based on independent analytical tools (XRD, SAED,
HRTEM, EDXS). The Ni-Os alloy formation explains well
the 5% and 2% contraction of the a and c lattice
parameters for alloyed Ni-Os nanoparticles as compared
to the corresponding bulk-Os as well as the Os-reference
nanoparticles (a = 0.274±0.001, c = 0.433±0.001 nm). A
decrease of the a and c lattice parameter values is indeed
expected after dissolving Ni (rNi = 0.124 nm) in the
(
s
TOF ) were estimated by calculating the ratio of the
number of surface atoms to the total number of atoms
based on the mean diameters (i.e., as obtained from TEM
images, Table 1) and used to evaluate the catalytic
properties of the NiIr
4
and NiOs
4
nanoparticles.
Nanoparticles of Ni, Ir, and Os were used as references.
These reference nanoparticles show very comparable
particle sizes, colloidal stability and surface conditioning
[
20]
structure of Os (rOs = 0.135 nm).
obtained NiOs composition is surprising since the
maximum Ni content in Ni-Os phases reaches only 13 at-
In fact, the here
(
Table 1; SI: Figures S1-S4; see Experimental Section).
4
These are crucial aspects in view of direct comparison of
the catalytic performance.
%
(at 1500 °C) according to the peritectic equilibrium
[20]
4 4
NiIr and NiOs nanoparticles were first tested for their
phase diagram.
Moreover, the maximum Ni content
catalytic activity in hydrogenation reactions using 1-
octene as a linear, terminal olefin with a sterically non-
hindered C=C bond (Figure 5a). The reaction was carried
was reported to decrease even further at lower
temperature reaching 11.2 at-% at 1400 °C and 9.2 at-%
[
20]
at 1200 °C, respectively.
With 20 at-% Ni the here
out at room temperature and 10 bar H
consumption was continuously recorded. Both bimetallic
nanoparticles, NiIr and NiOs , turned out as active
catalysts, resulting in TOF (after 3 h of reaction) of 5025
) (Table 2). Thus, NiIr turned
out as much more active as compared to NiOs
Figure 5b displays the H
hydrogenation of 1-octene with NiIr
2 2
pressure. The H
prepared NiOs nanoparticles, altogether, represent a
4
new alloy, whose formation can be ascribed to the low-
temperature synthesis with kinetic reaction control.
4
4
s
Altogether, the nanoparticles – NiIr
4
, NiOs
4
as well as
–1
(
NiIr
4
) and 313 h (NiOs
4
4
the Ni, Ir and Os references – exhibit comparable mean
diameters (5-10 nm) and very narrow size distributions.
Hereof, the NiIr , NiOs and Ni nanoparticles are slightly
4 4
larger (8-9 nm) as compared to the Ir and Os
nanoparticles (3-4 nm). An overview of diameters and the
relevant discussion is given in Table 1 and the Supporting
Information (SI: Figures S1-S4).
4
.
2
uptake over time for the
nanoparticles.
4
Table 2. Hydrogenation of 1-octene using NiIr
nanoparticles (at room temperature, 10 bar H ).
4
and NiOs
4
2
Substrate
mol]
Conversion
[%]
Time
[h]
TOF
[h ]
s
Nanoparticles
-1
[
NiIr
NiOs
Ni (10 mg)
4
(30 mg)
0.13
0.09
0.06
100
89
14
5025
313
4
(20 mg)
24
14
100
1131
We further employed cinnamaldehyde (CAL) as a
model compound to study the selective hydrogenation of

-unsaturated carbonyls. The selective hydrogenation
of unsaturated carbonyl compounds is a critical step in
the synthesis of various fine chemicals, in particular, in
[15]
the flavor, fragrance or pharmaceutical chemistry.
Instead of the desired, unsaturated alcohols, however,
the saturated aldehydes are the thermodynamically
favored products due to the higher free reaction enthalpy
of C=O (40 kJ/mol) compared to C=C (35 kJ/mol).
Therefore, efforts have been directed to enhance the
selectivity for the unsaturated alcohol, e.g., by additives,
alloys,
interactions.
stabilizers,
ligands,
or
metal-support
[14]
The hydrogenation of CAL proceeds via
different reaction pathways and stepwise hydrogenation
of the C=C or C=O bond to the intermediate saturated
aldehyde (i.e., hydrocinnamic aldehyde, HCAL) or the
unsaturated alcohol (i.e., cinnamic alcohol, CAOL),
4
Figure 4. NiOs nanoparticles: a) HAADF-STEM image with b) area-
EDX spectrum (dashed box area in (a)); c) HAADF-STEM image with
EDX line-scan with d) Ni and Ir composition profiles (along orange line
in (c)).
This article is protected by copyright. All rights reserved.

ChemCatChem
10.1002/cctc.201700168
accordingly, to the saturated alcohol (i.e., hydrocinnamic
medium (Figure 6b). In methanol, however, the formation
of acetals as by-products was favored, even in the
absence of the catalyst (Figure 7). Significant
acetalization (i.e., the formation of hemiacetal and acetal
products) was previously reported by others, e.g., in the
hydrogenation of furfural due to the reaction of the solvent
(i.e., alcohols such as methanol, ethanol or isopropanol)
alcohol, HCAOL) (Figure 6a). In general, the unpromoted
pure metals Os and Ir were previously reported to exhibit
high selectivities to the unsaturated alcohol CAOL, while
[
15]
pure Ni is known as rather unselective.
Recently,
intermetallic Ni-In or alloyed Ni-Sn catalysts were
described for the selective hydrogenation of unsaturated
[
21]
[22]
carbonyls.
and the aldehyde, even in absence of the Ni catalyst. It
was also reported that alcohol can serve as a hydrogen
[
23]
source
in
hydrogen
transfer
reactions.
Gaschromatographic (GC) analysis, on the other hand,
showed that the formation of acetals is reversible. Hence,
the acetals were here completely converted into reaction
products (i.e., HCAOL, CAOL, CAL) after a sufficiently
long reaction time. Lower amounts of acetals were
formed, if 2-propanol was used instead of methanol
(
Table 3). After 22 h of reaction, only the reaction
products and no acetals were determined by GC analysis.
However, the use of 2-propanol instead of methanol
considerably reduced both the catalytic activity and the
CAOL yield in the case of the NiIr
4
and NiOs
4
nanoparticles (Figure 7). In THF, where obviously no
acetals could be formed, the hydrogenation of the C=C
bond was favored over the hydrogenation of the C=O
bond, and HCAL was formed as the main product
(
Table 3).
Table 3. Hydrogenation of cinnamaldehyde (CAL) using NiIr
NiOs nanoparticles (Ni, Os and Ir nanoparticles as references; at
0°C, 10 bar H ; reaction time 3 h; unless specified otherwise).
4
and
4
Figure 5. Hydrogenation of 1-octene: a) Scheme of reaction
sequence; b) Time-dependent H gas uptake with NiIr nanoparticles
at room temperature, 10 bar H ).
8
2
2
4
(
2
CAOL yield
%]
Product selectivity [%]
TOF
[h ]
S
Cat.
e
-1
[
CAOL
HCAOL
HCAL
Other
72
a
NiIr
4
19
11
2
23
2
3
419
158
150
675
952
a
NiOs
4
28
3
1
19
3
5
19
2
66
59
73
a
Ni
a
Ir
14
48
22
52
b
Os
22
0
12
0
14
73
c
2
9
1
6
27f
35f
NiIr
4
f
f
f
f
60
7
33
0
10
c
4
50f
0
0
0
39
50f
5
3
NiOs
f
f
f
f
61
0
d
NiIr
4
1
28
12
60
0
25
a,c
b
d
20
mg; 24 mg; or 10 mg of the nanoparticle powder was
suspended in 1.5-3.0 mL hexane and used as catalyst. Substrate and
a,b
c
solvent: CAL (16 mmol) in 30 mL methanol; CAL (16 mmol) in 30
d
e
mL 2-propanol; CAL (8 mmol) in 15 mL THF; Other: Acetals
hemiacetal, unsaturated/saturated acetals); Reaction time 22 h.
f
(
Figure 6. Hydrogenation of cinnamaldehyde (CAL): a) Scheme of
reaction sequence; b) Time-dependent CAOL yield in the
hydrogenation of CAL with NiIr
media (methanol, 2-propanol, THF; at 80 °C, 10 bar H
4
nanoparticles using different reaction
).
2
The catalytic hydrogenation of CAL with the NiIr
NiOs nanoparticles as well as with the Ni, Ir and Os
references was investigated at a pressure of 10 bar H
4
and
4
2
and 80 °C using various reaction media (i.e., methanol, 2-
propanol, THF). The results of the catalytic experiments
are summarized in Table 3. The choice of the solvent was
shown to affect both the catalytic behavior of the
nanoparticles and the formation of by-products. An effect
of the solvent on the catalytic activity was also observed
by others. Thus, low activities were described for
hydrocarbons, whereas high activities were reported for
Figure 7. Product selectivity in the hydrogenation of CAL with
bimetallic NiIr and NiOs nanoparticles and their monometallic Ir, Os
and Ni counterparts (at 80 °C, 10 bar H ; reaction time: 3h; solvent:
methanol). Acetals (i.e., unsaturated/saturated hemiacetals or acetals)
were formed as byproducts (i.e., others).
[
14,18]
light alcohols (e.g., methanol, ethanol, 2-propanol).
In
4
4
2
our experiments, the highest activity and yield in CAOL
were obtained, if methanol was employed as reaction
This article is protected by copyright. All rights reserved.

ChemCatChem
10.1002/cctc.201700168
has been recently shown to selectively hydrogenate DPA
[
25]
to (E)-stilbene. Several, non-precious alloyed catalysts
have been also identified for the selective gas phase
[
3,26]
hydrogenation
of
acetylene.
Recently,
Ni
nanoparticles in ionic liquids have been reported as
selective nanocatalysts for the semihydrogenation of
[
27]
alkynes to (Z)-alkenes.
Figure 8. Time-depending selectivity in the hydrogenation of CAL with
a) NiIr and b) NiOs nanoparticles (at 80 °C, 10 bar H , solvent
methanol).
4
4
2
The highest yield in CAOL (i.e., 48% after 3 h) was
obtained for the Os-based nanocatalysts. In general,
alloying Ir and Os with Ni in the bimetallic NiIr
4
and NiOs
4
Figure 9. Hydrogenation of diphenylacetylene (DPA): a) Scheme of
reaction sequence; b) Time-depending conversion and selectivity in
particles, respectively, resulted in a decrease of the TOF
s
-
1
-1
the hydrogenation of DPA using the NiOs nanoparticles (at 80 °C, 10
4
from 675 (Ir) and 952 h (Os) to 419 (NiIr
4
) and 158 h
4
nanoparticles
2
bar H , solvent: THF).
(
NiOs ). Alloying Os with Ni in the NiOs
4
reduced the CAOL yield considerably to 11%. However,
almost no HCAOL (1%) was formed in the case of the
Here, the catalytic tests with NiIr4 and NiOs4 were
carried out at 80 °C and 10 bar H2[ using THF as a
20]
NiOs
4
nanoparticles as compared to the pure Os
reaction medium (Table 4, Figure 9b). After a reaction
nanoparticles (22%). In the case of the Ir-based
nanoparticles, a different behavior was observed. Alloying
of Ir with Ni lead to an increase in the CAOL yield ranging
from 14% for the pure Ir nanoparticles (3 h) to 16% for the
time of 1 h, the conversion was 7 and 45% for the NiIr4
and NiOs4 nanoparticles, respectively, in comparison to
9% for the Ni reference (Table 4). The resulting, TOF
s
-1
were 35 (NiIr ), 110 (NiOs ) and 21 h (Ni). Thus, the
4
4
bimetallic NiIr
4
nanoparticles (3 h) (Table 2). This is even
values are decreasing from NiOs4 over NiIr4 to the
monometallic Ni nanoparticles. (Z)-stilbene was the main
product for all nanocatalysts; the yield in (Z)-stilbene after
more remarkable since the pure Ni nanoparticles  as
expected  were rather selective for the formation of
HCAOL with a low yield in CAOL (2%). Figure 8 shows
1 h was 38% for NiOs
4
, but remained low for NiIr
4
(5%)
the time course of the selectivity for the alloyed NiIr
4
- and
and Ni (6%). As a conclusion, NiOs
4
is promising for
NiOs -based catalysts. In terms of direct comparison,
4
obtaining Z-stilbene in terms of conversion, selectivity and
TOF.
moreover, it is to be noted that – although synthesis was
adapted on as far as possible similar particle sizes – the
reference Ir and Os reference nanoparticles are smaller
Table 4. Hydrogenation of DPA with bimetallic NiOs
4
and NiIr
, 30
4
nanoparticles (Ni nanoparticles as a reference; at 80°C, 10 bar H
mL THF, 20 mg nanoparticle powder).
2
(
4 4
3-4 nm) than the bimetallic NiIr (9 nm) and NiOs (7 nm)
nanoparticles (Table 1). In terms of size and active
surface area, thus, the reference nanoparticles have the
Product selectivity [%]
Conversion
Time
[h]
TOF
[h ]
s
edge over the novel NiIr
Finally, the selective hydrogenation of alkynes with
the alloyed NiIr and NiOs nanoparticles was studied
4
and NiOs
4
nanoparticles.
Cat.
-1
[
%]
(Z)-
(E)-
DPE
10
stilbene
stilbene
4
4
NiIr
4
7
1
1
1
67
85
71
23
5
35
110
21
using diphenylacetylene (DPA) as a probe substrate.
DPA can be hydrogenated over (Z)- or (E)-stilbene to 1,2-
diphenylethane (DPE) (Figure 9a). (Z)-/(E)-stilbene are
interesting building blocks for [ dyes, liquid crystals,
NiOs
Ni
4
45
9
10
19
10
19]
fluorescent whitener and OLEDs. In general, Pd-based
bimetallic catalysts (e.g., Lindlar catalyst) were employed
[
24]
for the semihydrogenation of alkynes to alkenes.
Moreover, a variety of Rh-based intermetallic compounds
This article is protected by copyright. All rights reserved.

ChemCatChem
10.1002/cctc.201700168
and ethyl acetate. The product can be easily redispersed in
hexane.
Conclusion
NiOs
4
nanoparticles. 60 mg NiCl
O were dissolved in 20 mL of oleylamine. The solution
2
×6H
2
O
and 74 mg
Bimetallic NiIr
4
and NiOs
4
nanoparticles were
OsCl ×nH
3
2
prepared via oleylamine-driven reduction and exhibit
mean diameters of 8.9±1.3 and 6.8±1.4 nm at low degree
of agglomeration. Particle size and phase composition
were determined in detail by different analytical methods
including HRTEM, STEM, SAED, XRD and EDXS.
Accordingly, both nanoparticles exhibit a homogeneous
distribution of Ni-Ir and Ni-Os with a ratio of 1:4. The
bimetallic alloy nanoparticles NiIr
presented for the first time, which is especially
remarkable for NiOs since the bulk system Ni-Os exhibits
a miscibility gap for such high Ni contents.
To evaluate the catalytic properties of the novel NiIr
and NiOs nanoparticles, we have studied their catalytic
4
activity and selectivity in hydrogenation reactions using
three selected model substrates (i.e, 1-octene,
cinnamaldehyde and diphenylacetylene). Nanoparticles of
pure Ni, Ir, and Os with similar particle size and colloidal
stability were used as references. Both types of alloyed
was heated to 100 °C and stirred for 60 minutes in order to
remove moisture and oxygen. The color of the solution changed
from dark reddish-brown to dark blue. Thereafter, the reaction
mixture was heated to 300 °C with a heating rate of 26 K/min and
kept at this temperature for 30 minutes. Thereby, the color of the
mixture changed to dark brown. After natural cooling to room
temperature about 30 mL of ethyl acetate were added to the
product suspension followed by centrifugation. The black
precipitate was washed two times with a 1:3 mixture of hexane
and ethyl acetate. The product can be easily redispersed in
hexane.
4
and NiOs
4
are
4
2 2
Ni nanoparticles (reference). 140 mg NiCl ×6H O were
4
dissolved in 20 mL of oleylamine. The solution was heated to
100 °C and stirred for 60 minutes in order to remove moisture
and oxygen. Thereafter, the reaction mixture was heated to
3
00 °C with a heating rate of 26 K/min and kept at this
temperature for 10 minutes. Thereby, the color of the mixture
changed from green to dark brown. After natural cooling to room
temperature about 30 mL of ethyl acetate were added to the
product suspension followed by centrifugation. The black
precipitate was washed two times with a 1:3 mixture of hexane
and ethyl acetate. The product can be easily redispersed in
hexane.
Ir nanoparticles (reference). 80 mg IrCl
dissolved in 20 mL of ethylene glycol. The solution was heated to
50 °C with heating rate of 20 K/min and kept at this
temperature for 60 minutes. The color of the solution changed
from yellowish to dark brown. After natural cooling to room
temperature about 30 mL of ethanol were added to the product
suspension followed by centrifugation. The black precipitate was
washed two times with ethanol. The product can be redispersed
in Hexan.
Os nanoparticles (reference). 80 mg OsCl
dissolved in 20 mL of ethylene glycol. The solution was heated to
50 °C with heating rate of 20 K/min and kept at this
particles – NiIr
catalytic hydrogenation. Typically, the NiIr
nanoparticles show a higher activity and selectivity than
the pure Ni reference. Whereas the NiIr nanoparticles –
except for optional cost reduction – do not exhibit a
specific advantage in comparison to pure Ir, the NiOs
4
and NiOs
4
– are first shown in view of
4
and NiOs
4
3 2
×nH O and were
4
1
a
4
nanoparticles show promising features for the
hydrogenation of cinnamaldehyde and diphenylacetylene.
Although alloying Os with Ni in NiOs nanoparticles lead
4
to a decrease in both the yield of cinnamic alcohol and
the activity, a significantly increased selectivity for the
hydrogenation of the C=O bond to cinnamic alcohol was
achieved. Moreover, almost no hydrocinnamic alcohol
3 2
×nH O and were
1
a
4
was formed in the presence of NiOs . Interestingly,
temperature for 60 minutes. The color of the solution changed
from yellowish to dark brown. After natural cooling to room
temperature about 30 mL of ethanol were added to the product
suspension followed by centrifugation. The black precipitate was
washed two times with ethanol. The product can be redispersed
in Hexan.
intermediate acetals were completely converted into
useful products after sufficiently long reaction time.
Besides the selective hydrogenation of cinnamaldehyde,
NiOs turned out as promising for obtaining Z-stilbene in
4
terms of conversion, selectivity and TOF.
Besides the promising selectivity of NiOs
4
, alloying
a common,
Analytical methods
the precious metals (i.e., Ir, Os) with
Dynamic light scattering (DLS) was performed with
a
inexpensive base metal (i.e., Ni) at identical activity is
beneficial in terms of cost reduction. As the choice of the
solvent was shown to affect both the catalytic activity as
well as the selectivity, further improvement has to
address not only the catalyst itself but also the specific
experimental conditions (e.g., pressure, reactant
concentrations). In sum, the selectivities remained overall
high after alloying, which may open up interesting
possibilities in view of the development of cost effective
bimetallic catalytic systems.
Nanosizer ZS from Malvern Instruments (equipped with a He-Ne
laser (633 nm)), detection via non-invasive back-scattering at an
angle of 173 °, 256 detector channels, polystyrene cuvettes). For
analysis, the as-prepared nanoparticles were redispersed in
hexane. The obtained size distributions can be well fitted with
[
28]
lognormal distribution functions.
Scanning electron microscopy (SEM) was performed on a
Zeiss Supra 40 VP at an acceleration voltage of 20 kV and a
working distance of 3 mm, while for low-energy scanning
transmission electron microscopy (STEM) an acceleration voltage
of up to 30 kV and a working distance of 4 mm was used. The
samples were prepared on holey carbon-film copper-grids by
evaporating
a single drop of a dispersion of as-prepared
Experimental section
nanoparticles in hexane at room temperature in air. Energy-
dispersive X-ray (EDX) analysis was performed with an Ametek
EDAX device mounted on the above described Zeiss SEM Supra
Material synthesis
General aspects. All reactions were performed under
dynamic nitrogen purging. Purification and analysis were
performed under ambient atmosphere. Nickel(II)chloride
hexahydrate (97 %, Riedel de Haën); iridium(III)chloride hydrate
40 VP scanning electron microscope. For this purpose, powder
samples (300 mg) were pressed (50 tons) to dense pellets in
order to guarantee for a smooth surface and a quasi-infinite layer
thickness. These pellets were fixed with conductive carbon pads
on aluminum sample holders.
(99.9 %, ABCR); osmium(III)chloride hydrate (black xtl., ABCR);
oleylamine (80-90 %, Acros); ethylene glycol (extra pure, Riedel-
de Haёn). For better handling osmium(III)chlorid hydrate was
pestled and thereafter dried in vacuum for two hours.
High-resolution (HR) transmission electron microscopy
(TEM) and high-angle annular dark-field (HAADF) STEM are
3
conducted with an aberration-corrected FEI Titan 80-300
microscope at 300 kV. The experiments were performed with the
same samples that were used for overview STEM images.
Alternatively, HRTEM images were evaluated by calculating the
NiIr
4
nanoparticles. 60 mg NiCl
2 2
×6H O
and 149 mg
IrCl
3 2
×nH O were dissolved in 20 mL of oleylamine. The solution
was heated to 100 °C and stirred for 60 minutes in order to
remove moisture and oxygen. Thereafter, the reaction mixture
was heated to 300 °C with a heating rate of 26 K/min and kept at
this temperature for 10 minutes. Thereby, the color of the mixture
changed from light green to dark brown. After natural cooling to
room temperature about 30 mL of ethyl acetate were added to
the product suspension followed by centrifugation. The black
precipitate was washed two times with a 1:3 mixture of hexane
2-dimensional Fourier transformation – denoted as diffractogram
–
which yielded information on the crystal structure (lattice
parameters and crystal symmetry) of single nanoparticles.
Selected-area electron diffraction (SAED) patterns of nanoparticle
ensembles were taken with
microscope at 200 kV to investigate their crystal structure.
a Philips CM 200 FEG/ST
This article is protected by copyright. All rights reserved.

ChemCatChem
10.1002/cctc.201700168
Further information can be obtained from the Supporting
Information.
The chemical composition of single nanoparticles was
Keywords: NiIr
4
• NiOs
4
• Nanoparticle • Hydrogenation •
Cinnamaldehyde • Diphenylacetylene
investigated by energy-dispersive X-ray spectroscopy (EDXS)
3
performed with the FEI Titan 80-300 microscope at 300 keV
_
electron energy by using an EDAX Si(Li) detector. EDX spectra
are quantified with the FEI software package “TEM imaging and
analysis” (TIA) version 3.2. Using TIA, element concentrations
were calculated on the basis of a refined Kramers’ law model,
which includes corrections for detector absorption and
background subtraction. Further information can be obtained from
the Supporting Information.
[
1] Recent reviews: a) K. An, G. A. Somorjai, Catal. Lett. 2015, 145,
2
33-248. b) A. K. Singh, Q. Xu, ChemCatChem 2013, 5, 652-676.
c) M. Sankar, N. Dimitratos, P. J. Miedziak, P. P. Wells, C. J.
Kiely, G. J. Hutchings, Chem. Soc. Rev. 2012, 41, 8099-8139.
[2] A. Meffre, V. Iablokov, Y. Xiang, R. Barbosa, P. F. Fazzini, V.
Kelsen, N. Kruse, B. Chaudret, Catal. Lett. 2015, 145, 373-379.
[3] M. Armbrüster, K. Kovnir, M. Friedrich, D. Teschner, G.Wowsnick,
M. Hahne, P. Gille, L. Szentmiklósi, M. Feuerbacher, M. Heggen,
F. Girgsdies, D. Rosenthal, R. Schlögl, Y. Grin, Nature Mater.
X-ray powder diffraction (XRD) analysis was carried out on a
Stoe
Stadi-P
diffractometer
using
Cu-Kα1
radiation
2012, 11, 690-693.
( = 0.1540598 nm) monochromated by a focusing Ge crystal. A
[
4] J. R. Renzas, W. Huang, Y. Zhang, M. E. Grass, G. A. Somorjai,
Catal. Lett. 2011, 141, 235-241.
5] G. H. Wang, J. Hilgert, F. H. Richter, F. Wang, H. J. Bongard, B.
Spliethoff, C. Weidenthaler, F. Schueth, Nature Mater. 2014, 13,
position sensitive detector [Stoe IP-PSD, 70 °(2) angular
aperture] was used to record the XRD patterns with a step size of
[
0.03 °(2). The detector channels were calibrated with the line-
positions of a Si standard. Further information can be obtained
from the Supporting Information.
293-300.
[
6] G. J. Hutchings, Catal. Today 2014, 238, 69-73.
Thermogravimetry (TG) measurements were performed with
[7] a) H.-L. Jiang, Q. Xu, J. Mater. Chem. 2011, 21, 13705-13725. b)
S. K. Singh, M. Yadav, S. Behrens, P. W. Roesky, Dalton Trans.
2013, 42, 10404-10408.
[8] R. Kumar Rai, K. Gupta, S. Behrens, J. Li, Q. Xu, S. K. Singh,
ChemCatChem 2015, 7, 1806-1812.
a NETZSCH STA 449 F3 applying α-Al
O
2 3
as crucible material.
The samples were heated under N
heating rate of 5 °C/min.
2
flow to 1400 °C with a
Catalytic experiments
[9] a) H. N. Nong, H. S. Oh, T. Reier, E. Willinger, M. G. Willinger, V.
Petkov, D. Teschner, P. Strasser, Angew. Chem. Int. Ed. 2015,
Hydrogenation reactions were carried out in a stainless steel
autoclave (200 mL). The autoclave was equipped with a telfon
inlay, a mechanical blowing stirrer (teflon) and baffles (stainless
steel) to achieve intimate mixing between the gas and the liquid
phase, a thermocouple and a heating bath. The catalyst and the
organic substrate were loaded in the autoclave under argon
atmosphere. Dry solvents were used in all catalytic experiments.
In a typical experiment, the nanoparticles were dispersed in
hexane (3-5 mL) using an ultrasonic bath, mixed with the organic
substrate and added to the autoclave reactor. After heating the
mixture to the reaction temperature, the stirrer was started
5
4, 2975-2979. b) H. N. Nong, L. Gan, E. Willinger, D. Teschner,
P. Strasser, Chem. Sci. 2014, 5, 2955-2963.
[10] a) P. Zhao, N. Cao, J. Su, W. Luo, G. Sheng, ACS Sustainable
Chem. Eng. 2015, 3, 1086-1093. b) C. Cakanyildirim, U. B.
Demirci, T. Sener, Q. Xu, P. Miele, Int. J. Hydrogen Energy 2012,
37, 9722-9729. c) S. K. Singh, Q. Xu, Chem. Commun. 2010, 46,
6545-6547.
[
11] a) K. Sasaki, K. A. Kuttiyiel, L. Barrio, D. Su, A. I. Frenkel, N.
Marinkovic, D. Mahajan, R. R. Adzic, J. Phys. Chem. 2011, 115,
9894-9902. b) J. Liao, W. Ding, S. Tao, Y. Nie, W. Li, G. Wu, S.
Chen, L. Li, Z. Wei, Chin. J. Catal. 2016, 37, 1142-1148. c) W.
Zhang, L. Li, W. Ding, S. Chen, H. Wang, Z. Wei, J. Mater. Chem.
A 2014, 2, 10098-10103.
(
1200 rpm). The reaction was initiated by introducing hydrogen
into the reactor. During catalytic experiments, the hydrogen
pressure was kept constant at 10 bar and hydrogen was
continuously supplied to the reactor by a gas burette (500 mL,
Parr). The consumption of hydrogen was recorded automatically
based on the pressure drop in the gas burette. The selectivity and
conversion in the hydrogenation of cinnamaldehyde and
[
[
12] H. Ziaei-Azad, N. Semagina, ChemCatChem 2014, 6, 885-894.
13] W. Lin, H. Cheng, L. He, Y. Yu, F. Zhao, J. Catal. 2013, 303, 110-
116.
[
14] R. Marcos Esteban, K. Schütte, P. Brandt, D. Marquardt, H.
Meyer, F. Beckert, R. Mülhaupt, H. Kölling, C. Janiak, Nano-
Structures & Nano-Objects 2015, 2, 11-18.
diphenylacetylene were determined by
detection gas chromatograph (GC-FID, Agilent) equipped with a
J&W SCIENTIFIC DB5 column (Agilent Technology,
a
flame ionization
[15] L. J. Durndell, C. M. A. Parlett, N. S. Hondow, M. A. Isaacs, K.
Wilson, A. F. Lee, Sci. Rep. 2015, 5, 1-9.
[16] P. Gallezot, D. Richard, Catal. Rev. Sci. Eng. 1998, 40, 81-126.
[17] S. C. Yang, N. Chen, P. Nash, Phase Diagrams of Binary Nickel
Alloys, ASM, Materials Park, OH, 1991, 181-182.
30 m×0.25 mm, 0.25 µm film thickness) and a Stabilwax-Da
column (30 m×0.25 mm, 0.25 µm film thickness), respectively.
The determination of the turn over frequency (TOF) requires
the quantitative determination of the number of active centers of
[
18] a) J. I. Langford, R. Delhez, T. H. de Keijser, E. J. Mittemeijer,
Aust. J. Phys. 1998, 41, 173-178. b) R. Delhez, T. H. de Keijser,
E. J. Mittemeijer, Fresenius Z. Anal. Chem. 1988, 312, 1-16.
the catalyst, which is typically not [
a
simple task for
29]
[19] E. Bucher, W. F. Brinkman, J. P. Maita, A. S. Cooper, Phys. Rev.
B 1970, 1, 274-277.
heterogeneous catalysts or nanoparticles. Therefore, the TOF
of heterogeneous catalysts or nanoparticles have been often
related to the total amount of the active phase (moles of metal
used) or its surface area. Typically, only the atoms exposed on
the nanoparticle surface (or a fraction of them) are catalytically
active. In our experiments, the TOF based on surface atoms
[
20] a) T. Y. Velikanova, T. G. Mazhuga, O. L. Semenova, P. S.
Martsenyuk, V. M. Vereshchaka, Powder Metallurgy and Metal
Ceramics 2002, 41, 288-295. b) A. A. Samadi, M. Fedoroff, Scri.
Metall. 1977, 11, 509-512.
[21] a) C. Li, Y. Chen, S. Zhang, S. Xu, J. Zhou, F. Wang, M. Wei, D.
Evans, X. Duan, Chem. Mater. 2013, 25, 3888-3896. b) K.
Rodiansono, S. Khairi, T. Hara, N. Ichikunia, S. Shimazu, Catal.
Sci. Technol. 2012, 2, 2139-2145.
(
TOF
compare the catalytic performance of the nanoparticle catalysts.
The total average atom number (N ) and the number of surface
atoms (N were calculated using the average nanoparticle
s
) were calculated according to equation (1) and used to
T
[22] H. Jeong, C. Kim, S. Yang, H. Lee, J. Catal. 2016, 344, 609-615.
s
)
[30]
[23] G.-H. Wang, X. Deng, D. Gu, K. Chen, H. Tüysüz, B. Spliethoff,
H.-J. Bongard, C. Weidenthaler, W. Schmidt, F. Schüth, Angew.
Chem. Int. Ed. 2016, 55, 11101-11105.
diameter obtained by TEM analysis.
ꢄꢅꢆꢇꢈꢉꢊꢋꢅꢆꢌꢍꢎꢏꢐꢆꢑꢒꢓꢔꢕꢍꢖꢅꢗꢏꢌ
ꢀꢁꢂ ꢃ
ꢡ
ꢦꢧꢨꢩ
(1)
ꢢ
ꢆꢘꢙꢚꢛꢜꢝꢞꢛꢚꢛꢜꢟꢠꢚꢍꢖꢅꢗꢏꢐ ꢐꢤꢋꢖꢈꢍꢥꢏ
ꢡꢣ
[24] T. Komatsua, K. Takagib, K. Ozawa, Catal. Today 2011, 164,
1
43-147.
25] S. Furukawa, A. Yokoyama, T. Komatsu, ACS Catal. 2014, 4,
581-3585.
[
[
3
Acknowledgments
26] F. Studt, F. Abild-Pedersen, T. Bligaard, R. Sørensen, C.
Christensen, J. Nørskov, Science 2008, 320, 1320-1322.
27] H. Konnerth, M. Precht, Chem. Commun. 2016, 52, 9129-9132.
28] L. B. Kiss, J. Söderlund, G. A. Niklasson, C. G. Granqvist,
Nanotechnol. 1999, 10, 25-28.
The
authors
thank
the
Deutsche
[
[
Forschungsgemeinschaft (DFG) for funding in the Priority
Program SPP1708 “Synthesis near room temperature”.
[29] P. E. Strizhak, Theoret. Exp. Chem. 2013, 49, 2-21.
[30] H. Hosseini-Monfared, H. Meyer, C. Janniak, J. Mol. Catal. A
2013, 372, 72-78.
This article is protected by copyright. All rights reserved.

ChemCatChem
10.1002/cctc.201700168
Entry for the Table of Contents
FULL PAPER
Bimetallic is more selective than
monometallic – The bimetallic NiIr
and NiOs alloy nanoparticles are first
4
studied and show promising catalytic
performance in hydrogenation
reactions.
Alexander Egeberg, Christine Dietrich,
Christian Kind, Radian Popescu,
Dagmar Gerthsen, Silke Behrens and
Claus Feldmann*
4
Page No. – Page No.
Bimetallic NiIr
4
and NiOs
4
Alloy
Nanoparticles and their Catalytic
Performance
Reactions
in
Hydrogenation
This article is protected by copyright. All rights reserved.