Synthesis and characterization of nearly monodisperse Pt nanoparticles for C1 to C3 alcohol oxidation and dehydrogenation of dimethylamine-borane (DMAB)

Article abstract of DOI:10.1166/jnn.2016.11683

Highly efficient nearly monodisperse Pt NPs catalyze C1 to C3 alcohol oxidation with very high electrochemical activities and provides one of the highest catalytic activities (TOF = 21.50 h^-1) in the dehydrogenation of DMAB at room temperature.

Full text of DOI:10.1166/jnn.2016.11683

Article
Journal of
Nanoscience and Nanotechnology
Vol. 16, 5944–5950, 2016
Copyright © 2016 American Scientific Publishers
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Printed in the United States of America
Synthesis and Characterization of Nearly Monodisperse
Pt Nanoparticles for C1 to C3 Alcohol Oxidation and
Dehydrogenation of Dimethylamine-borane (DMAB)
Esma Erken1, Yunus Yıldız1, Benan Kilbas¸2, and Fatih S¸en1ꢀ∗
1Biochemistry Department, Dumlupinar University, 43100 Kütahya, Turkey
2Chemistry Department, Duzce University, 81620 Duzce, Turkey
Highly efficient nearly monodisperse Pt NPs catalyze C1 to C3 alcohol oxidation with very high
electrochemical activities and provides one of the highest catalytic activities (TOF = 21.50 h−1) in
the dehydrogenation of DMAB at room temperature. The exceptional stability towards agglomer-
ation, leaching and CO poisoning for the prepared catalyst allow these particles to be recycled
and reused in the catalysis of both DMAB dehydrogenation and C1 to C3 alcohol oxidation. After
four subsequent reaction and recovery cycles, catalyst retained ≥80% activity towards the com-
plete dehydrogenation of DMAB. The prepared catalyst structures were determined by the X-ray
photoelectron spectroscopy (XPS), X-ray diffraction (XRD), atomic force microscopy (AFM) and
transmission electron microscopy (TEM) respectively.
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Keywords: Direct Alcohol Fuel Cells (DAFCs), Atomic Force Microscopy (AFM), Transmission
Copyright: American Scientific Publishers
Electron Microscopy (TEM), Platinum NPs, X-ray Photoelectron Spectroscopy.
1. INTRODUCTION
8.00 kWh kg−1) provides the fuel cells with a potential
candidate for this type of fuel.20ꢀ21 2-propanol might also
be a convenient fuel, not only the high energy content
and availability, but also fewer oxidation products, faster
oxidation kinetics, and lower tendency for cross over.22ꢀ23
Although these alcohols show promise as alternative fuels,
their slow reaction kinetics in acidic environments empha-
size the need for a catalyst.24 Recently, Pt nanocatalyst
has been mostly used to activate these alcohols. These
nanoparticles can also be used as catalyst for the dehydro-
genation of amine borane derivatives which have consider-
able attention in hydrogen storage. For this purpose, nearly
monodisperse Pt NPs have been synthesized and were
also well characterized by using some surface characteri-
zation techniques such as X-ray diffraction (XRD), X-ray
photoelectron spectroscopy (XPS), Transmission electron
microscopy (TEM), Atomic force microscopy (AFM) and
reported their catalytic activities for both alcohol oxidation
and the dehydrogenation of ammine borane adducts.
Even fossil fuels are still primary energy consumption
in the world; sustainable renewable energy sources are
becoming more popular due to the environmental problems
and more energy demands.1–5 Nowadays, direct type fuel
cell has attracted interest for an electrical power source
of the next generation, especially for the compact system.
Fuel cells convert chemical energy directly into electrical
energy with high efficiency and low emission of pollutants
and can be used for stationary energy generation as well
as for vehicles and portable devices.6–10 Direct methanol
fuel cells (DMFCs) have been the subject of great inter-
est in recent years due to their potential application in
electric vehicles and portable power sources.11–14 The elec-
trocatalytic oxidation of methanol has been thoroughly
investigated, since methanol is an essential and consider-
able reagent for direct methanol fuel cells (DMFC).15–17
Alternatively, ethanol is another important fuel due to
its non-toxic property and it can easily be produced in
large quantity by the fermentation of sugar-containing
raw materials, agricultural products and biomass.18ꢀ19 In
addition, the high theoretical mass energy density (about
2. EXPERIMENTAL DETAILS
2.1. Materials
PtCl4 (99%) was purchased from Alfa; tetrahydrofu-
ran (THF, 99.5%), methanol (≥99.5), ethanol (99.9%),
∗Author to whom correspondence should be addressed.
5944
J. Nanosci. Nanotechnol. 2016, Vol. 16, No. 6
1533-4880/2016/16/5944/007
doi:10.1166/jnn.2016.11683

Erken et al.
Synthesis and Characterization of Nearly Monodisperse Pt Nanoparticles
2-propanol (%99.8) and HClO4 (60%) were obtained
from Merck; lithium triethylborohydride (superhydride,
1.0 M) and N ,N -dioctyl-1-octanamine were obtained from
Aldrich and activated carbon was purchased from Cabot
Europe Ltd.
nanoparticles. Then, the solid was dried under vacuum at
room temperature.
2.2.2. Catalytic Activity of Pt NPs in the
Dehydrogenation of DMAB
Transmission electron microscopy (TEM) images were
obtained on a JEOL 200 kV TEM instrument. Samples
catalyst onto 400-mesh copper grids, ∼0.5 mg/ml CCl4
may be prepared by placing a drop of the solution and
analysis prior to solvent was allowed to evaporate.
Thermo Scientific spectrometer was used for X-ray pho-
toelectron spectroscopy (XPS) analysis and Kꢁ lines of
Mg (1253.6 eV, 10 mA) was utilized as a X-ray source.
XPS peak has been fitted by using Gaussian function.
For this purpose, the Pt 4f region of the spectrum was
analyzed and the fitting of XPS peak was performed by
Gaussian-Lorentzian method. The relative intensity of the
species was estimated by calculating the integration of
each peak, after smoothing, subtraction of the Shirley-
shaped background. In the XPS spectrum, accurate binding
energies ( 0.3 eV) were determined by referencing to the
C 1s peak at 284.6 eV.
The dehydrogenation of DMAB reaction was typically
occurred in a three-necked reaction flask connected to a
dry nitrogen tank. Catalytic activites of Pt NPs were deter-
mined by measuring the amount of hydrogen generated
by dehydrogenation of DMAB. Typically, 31.0 mg DMAB
(1.0 mmol) was dissolved in 4.0 ml THF solution in a
reaction flask and then 1.0 ml THF solution of Pt NPs was
transferred into the reaction flask thermostated in 25ꢃ0
ꢀ
0ꢃ1 C. Thereafter, about 0.5 mL aliquots of the reaction
solution in the reactor is removed with a glass Pasteur
pipette and 1.0 g of CDCl3 was added in a quartz NMR
tubes.
2.2.3. Reusability Performance of Pt NPs in the
Dehydrogenation of DMAB
After the first run of the dehydrogenation of 1 mmol
DMAB with Pt NPs, three-necked reaction flask detached
from the line and the connected to a vacuum line. After
evaporation of volatiles, the solid residue was weighed and
re-used in the dehydrogenation of 1 mmol DMAB reaction
under the same conditions. (25ꢃ0 0ꢃ1 ꢀC). This procedure
A Panalytical Emperian diffractometer with Ultima
theta–theta high resolution goniometer, having an X-ray
generator (Cu K radiation, k = 1.54056 Å) and operating
condition of 45 kV and 40 mA, was employed in XRD
analysis.
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was followed up to four catalytic runs.
AFM measurements were performed with the sample at
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Copyright: American Scientific Publishers
ambient temperature using Park Systems AFM XE-100E
2.2.4. Mercury (Hg(0)) Poisoning of Pt NPs in the
Dehydrogenation of DMAB
operated in the intermittent contact (“tapping”) mode to
see the surface topographies of the prepared catalyst. For
this measurements, firstly, we prepare a sample for AFM
by first diluting the product solutions by 300-fold or more
with DI water and place 2.5 ꢂL of the final solution
directly onto the freshly cleaved mica disk (supporting
material) and a solvent was dried in a vacuum at room
temperature for at least 12 h.
Experimental Hg (300 eq.) containing 5.0 mL THF solu-
tion containing Pt NPs were added into a reaction flask
and the mixture was stirred for 4 hours. Then, this solu-
tion was used in the dehydrogenation of 1.0 mmol DMAB
under the same conditions given above.
3. RESULTS AND DISCUSSION
3.1. Characterization of Pt NPs
Pt NPs were readily and reproducibly obtained by super-
hydride reduction of PtCl4 in an anhydrous THF solution
of N ,N -dioctyl-1-octanamine ligand at room temperature.
Cyclic voltammetry measurements have been performed
by a microcomputer-controlled potentiostat/galvanostat,
(Gamry Reference 3000), at room temperature. At least
ten cyclic voltammogram measurements were recorded for
the prepared catalyst.
The amount of platinum in prepared catalyst was deter-
mined by Leeman Lab ICP.
11B NMR spectra were taken on a Bruker Avance DPX
400 MHz spectrometer (128.2 MHz for 11B NMR).
2.2. Methods
2.2.1. The Preparation of Pt NPs
Pt NPs were formed by superhydride reduction method
in an ultrasonic sonicator. Shortly, PtCl4 0.25 mmol
(8.1 mg of anhydrous tetrahydrofuran) and 0.25 mmol
of N ,N -dioctyl-1-octanamine was dissolved and reduced
with 0.25 mmol superhydride in an ultrasonic conditions.
A brown-black solid has proved the formation of platinum
Figure 1. XRD of catalyst Pt NPs.
J. Nanosci. Nanotechnol. 16, 5944–5950, 2016
5945

Synthesis and Characterization of Nearly Monodisperse Pt Nanoparticles
where
Erken et al.
k = a coefficient (0.9)
ꢇ = the wavelength of X-ray used (1.54056 Å)
ꢈ = the full width half-maximum of respective diffraction
peak (rad)
ꢄ = the angle at the position of peak maximum (rad).
X-ray photoelectron spectroscopy (XPS) was used to
determine the surface composition and the oxidation state
of Pt. The doublet consists of two double Pt 4f photo-
electron spectrums for the prepared catalyst as shown in
Figure 2. The ratio of the 4f7/2/4f5/2 signals for Pt NPs
was found to be 4/3, which agree with the literature.25–27
The line at 71.0–74.1 eV is undoubtedly due to Pt(0),
while the higher binding energy component, 74.3–77.6 eV,
is most probably due to the presence of Pt(IV) species
such as PtO2 or Pt(OH)4. This result indicate that Pt is
mostly in zero oxidation state (%70.6) in our catalyst.
Atomic force microscopy (AFM) was used to see
the height and lateral diameter distribution. AFM results
showed that the height value of Pt NPs is ∼3.76 nm that
exhibit similar value with the XRD and TEM results as
shown in Figure 3. It should be noted, however, that AFM
lateral diameter of the prepared catalyst is found as ∼54.3
and much larger than the size of those obtained by the
XRD and TEM results due to likely tip contamination
and/or the tip convolution.27–29
Figure 2. Pt 4f electron spectra of Pt NPs.
Absence of capping ligand caused to both agglomeration
of the initially formed Pt NPs and precipitation out of the
THF solution. In contrast, the presence of ligand provided
stable Pt NPs for a long time. Afterwards, Pt NPs were
cleaned up dry ethanol to remove excess ligand and was
obtained as solid by evaporation of solvent under vacuum
atmosphere.
The preliminary characterization of Pt NPs were per-
formed by ICP-OES, XRD, TEM, HRTEM, AFM and
XPS. XRD data indicates that Pt NPs exhibit diffraction
patterns as illustrated in Figure 1. The diffraction peaks
The high resolution electron micrograph (HRTEM) and
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at 2ꢄ = 39ꢃ85, 46.27, 67.68, 81.56 and 85.98 are mainly
particle size histogram of the prepared catalyst are shown
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due to Pt (111), (200), (220), (311), and (320) respec-
tively, planes of the face-centered cubic (fcc) crystal lat-
tice of platinum. (JCPDS-ICDD, Card No. 04-802) The Pt
(220) diffraction peak of the prepared catalyst was used
to calculate the lattice parameter (ꢁPt) values and average
crystallite dimensions of the metal particles. The lattice
parameter was found to be 3.930 Å using the equation in
literature25 which is in good agreement with 3.923 Å for
pure Pt. The average crystallite size of the platinum par-
ticles was calculated approximately 3ꢃ93 0ꢃ42 nm using
the following equation.26
Copyright: American Scientific Publishers
in Figure 4 which is representative of the morphology
of the prepared catalyst as well. Uniform distribution of
the catalyst particles with a relatively narrow range on
activated carbon support was observed. HRTEM results
also indicated that most of the particles are in a spher-
ical shape, and no agglomerations are observed in our
catalyst. Figure 4 also displays the representative atomic
lattice fringes obtained by high resolution transmission
electron microscopy for Pt NPs. As a result of these
fringes, Pt (1 1 1) plane was observed with spacing of
0.225 nm on the prepared catalyst, respectively, which is
very close to nominal Pt (1 1 1) spacing of 0.227 nm,
respectively.30
kꢇ
d ꢅÅꢆ =
ꢈcosꢄ
(a)
(b)
(c)
35
30
25
20
15
10
5
40
35
30
25
20
15
10
5
0
0
Particle height (nm)
Particle size (nm)
Figure 3. AFM images of Pt NPs (a). Histogram of height of particles obtained from AFM data (b). Histogram of lateral diameter of particles
obtained from AFM data (c).
5946
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Erken et al.
Synthesis and Characterization of Nearly Monodisperse Pt Nanoparticles
Figure 4. High resolution transition electron micrograph and particle
size histogram of Pt NPs.
Figure 5. Anodic part of the cyclic voltammogram of Pt NPs in 0.1 M
HClO4 + 0ꢃ5 M methanol, ethanol and 2-propanol at room temperature.
Scan rate is 50 mV/s.
3.2. Electrochemical Measurements
The prepared catalyst has a much defined typical oxygen
and hydrogen adsorption/desorption regions which reflects
the electrochemical surface area (ECSA) of the Pt NPs cat-
alyst. In general, ECSA of the catalyst is one of the most
important parameters to determine the catalytic properties
of electrocatalyst for alcohol electro-oxidation since this
reaction is surface-sensitive and could be determined from
the integrated charge in the hydrogen adsorption region of
the cyclic voltammogram using the following formula;31ꢀ32
Moreover, roughness factor, Rf (m2 g−1 Pt cm−2) can be
used to describe the enhancement of the real ECSA in
comparison with the geometric area, Ag (cm2)35
ECSA
Rf =
Ag
CSA, ECSA, Rf and % Pt utility for the prepared catalyst
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were summarized in Table I. It can be seen that Pt NPs
has higher active surface area, Rf, and % Pt utility com-
Q ꢅmCꢆ
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ECSA =
2
Copyright: American Scientific Publishers
Pt loading on electrode×0ꢃ21 mC/cm
pared to the commercial Pt (ETEK) catalyst which could
be attributed to the higher catalytic activity.
where Q is the amount of charge exchanged during
the electro adsorption of hydrogen atoms on Pt and
0.21 mC/cm2 represents the charge required to oxidize
a monolayer of H2 on platinum. The Chemical Surface
Areas (CSA) of the catalyst were calculated using the fol-
lowing equation, assuming homogenously distributed and
spherical particles,33
When methanol, ethanol and 2-propanol were added to
the 0.1 M HClO4 electrolyte solution the classical alco-
hol oxidation response was observed for the prepared cat-
alyst. Figure 5 indicates the anodic parts of the cyclic
voltammogram for the prepared catalyst against oxidation
of methanol, ethanol and 2-propanol, respectively. Consid-
ering the electrochemical oxidation results, it is possible
6 ×103
CSA =
ꢉ×d
where d is the mean Pt crystalline size in Å (from the XRD
results) and ꢉ is the density of Pt metal (21.4 g/cm2ꢆ.34
Comparing these two areas (ECSA and CSA), it is possible
to estimate the Pt utilization efficiency (%) using
ECSA
Utilization ꢅ%ꢆ =
∗100
CSA
Table I. The comparisons of particle size, ECSA, CSA and % Pt utility
for the Pt NPs with commercial Pt catalysts.
Particle
size (nm)
ECSA
(m2/g)
Roughness
factor (Rf)
CSA
(m2/g)
Pt utility
(%)
Figure 6. % conversion versus time graph for the catalytic dehydro-
genation of DMAB in THF at room temperature starting with 7.5% mol
of Pt NPs and PtCl4 .
Pt NPs
Pt (ETEK)
3.73
2.70
59.40
50.60
121.2
103.3
71.34
103.0
83.26
49.10
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5947

Synthesis and Characterization of Nearly Monodisperse Pt Nanoparticles
3.3. Catalytic Activity of Pt NPs in the
Erken et al.
Dehydrogenation of Dimethylamine-borane
(DMAB)
Pt NPs were also examined in the dehydrogenation of
DMAB at 25 0ꢃ1 ꢀC. Hydrogen progression starts
immediately with a first initial turnover frequency of
21.50 h−1 and continues until 1 equivalent H2 per mol
DMAB released. It is observed only ∼8% conversion
after an induction time period (∼10 min.) when PtCl4
is used as pre-catalyst under the same conditions in
the dehydrogenation of DMAB (Fig. 6), at the end
of the reaction, the Pt particles starts to agglomerate
within 10 min. Since weakly coordinating chloride anion
without stabilizer does not provide adequate stabiliza-
tion for Pt(0) nanoparticles.38 After the dehydrogenation
reaction of DMAB (at 1.0 equiv. H2 generation), NMR
shows the complete conversion of (CH3ꢆ2NHBH3 (ꢊ =
∼12ꢃ4 ppm) to [(CH3ꢆ2NBH2]2 (ꢊ = ∼5 ppm) even at
room temperature.27 Besides, the DMAB dehydrogenation
of Pt NPs queried by performing experiments heteroge-
neous nature of mercury poisoning, and the reaction was
found to be completely stopped by addition of 300 Eq. Pt
NPs as a heterogeneous catalyst is moving forward Hg (0)
per Pt.
Figure 7. % conversion versus time plot for Pt NPs (7.5% mol) cat-
alyzed dehydrogenation of DMAB in THF at various temperatures.
to conclude that Pt NPs has very high catalytic activity
(∼0.65 A/mg Pt at 0.72 V for methanol, ∼0.30 A/mg
Pt at 0.66 V for ethanol and 0.76 A/mg Pt at 0.56 V
for 2-propanol) towards C1 to C3 alcohol oxidation reac-
tions. Moreover, the activity of this catalyst is about 8.64,
12.0 and 10.1 times higher than commercially available
E-TEK Pt ones for methanol, ethanol and 2-propanol oxi-
dation reactions, respectively36ꢀ37 due to the higher ECSA,
roughness factor and Pt(0) to Pt(IV) ratio of the prepared
3.4. Detection of Activation Parameters (Ea,
ꢋH#, and ꢋS#) for Pt NPs Catalyzed
Dehydrogenation of DMAB
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catalyst. Furthermore, it is clear that the current densi-
ties of 2-propanol oxidation at corresponding potentials are
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The stoichiometric ratio of produced H to (CH ꢆ NHBH
Copyright: American Scientific Publishers
2
3
2
3
higher than that of methanol and ethanol oxidation on our
catalyst due to the lower reaction rate of the intermediate
formation for 2-propanol than that of other alcohols. This
can be explained by a direct reaction path from 2-propanol
to acetone, which does not go through an intermediate.
Therefore, the performance of our catalyst for 2-propanol
oxidation is higher than that of other alcohols in this
study. Besides, the similar trend was observed for the onset
potentials of C1 to C3 alcohols oxidations. Namely, the
overall oxidation rate of 2-propanol was higher than the
other alcohols.
was expressed for the catalytic dehydrogenation of DMAB
starting with Pt NPs and the rate constants (kobsꢆ of hydro-
gen generation were measured from the linear portions of
the plots given in Figure 7 at four different temperatures in
the range ꢀof 20–35 ꢀC. It is found that even at low temper-
ature (20 C), Pt NPs is able to catalyze the dehydrogena-
tion of DMAB at 1.0 equiv. of H2 generation. The acti-
vation energy (Ea = 48.36 kJ mol−1), activation enthalpy
(ꢋH# = 45ꢃ82 kJ mol−1), and activation entropy (ꢋS# =
−112ꢃ99 J mol−1
K
−1) have been calculated by using from
the Arrhenius39 and Eyring40 plots (Fig. 8). The activation
–
–
–
–
–
–
Figure 8. (a) Arrhenius and (b) Eyring plots for Pt NPs catalyzed dehydrogenation of DMAB at various temperature.
J. Nanosci. Nanotechnol. 16, 5944–5950, 2016
5948

Erken et al.
Synthesis and Characterization of Nearly Monodisperse Pt Nanoparticles
energy value (48.36 kJ mol−1ꢆ provided by Pt NPs is not
only higher than Rh(0) nanoparticles (34 kJ mol−1), but
still smaller than the activation energies reported in the lit-
erature for the same reaction (Table II). Moreover, there is
an associative mechanism in the transition issues for the
catalytic dehydrogenation of DMAB between the higher
negative value of the activation entropy and the small value
of the activation enthalpy.
3.5. Reusability Performance of Pt NPs in the
Catalytic Dehydrogenation of DMAB
Pt NPs were also tested for the isolability and recycling
in the dehydrogenation of DMAB at room temperature.
After the complete dehydrogenation of DMAB, Pt NPs
were isolated as black solid by drying in a vacuum and
then bottled under N2 atmosphere. Interestingly, the iso-
lated Pt NPs were still active in the dehydrogenation of
DMAB. Even if at the fourth catalytic period, they retain
≥80% of their initial activity (Fig. 9). This indicates that
the prepared platinum nanoparticles can be isolable, bot-
tleable, and redispersible for a long time. In other words,
they can be repeatedly used as active catalyst in the dehy-
drogenation of DMAB. The slight decrease in catalytic
activity may be attributed to the formation of a precipi-
tate of bulk Pt(0) metal. This becomes visible at the end
of the 4th catalytic run, finally yielding a clear, colorless
Figure 9. % conversion versus time graph for Pt NPs (7.5% mol) cat-
alyzed dehydrogenation of DMAB in THF at room temperature for 1st
and 4th catalytic runs.
(i.e., Pt(0) nanoparticle free) by increasing boron products,
which decreases reach of active sites.27 The apparent ini-
tial TOF value of Pt NPs (21.50 h−1ꢆ is higher than the
majority of those of other heterogeneous and homogeneous
catalysts as shown in Table II, apart from the prior best
heterogeneous27 (60 h−1) and homogeneous33 (420 h−1
)
catalysts. As far as we know, our catalyst is the one of
the few examples of an isolable and reusable nanocatalysts
used for DMAB dehydrogenation reaction in literature.27
Most importantly, the reusability performance of Pt NPs is
better than the one of Rh(0) nanocatalyst previously known
as the most active catalyst.27
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Table II. Catalysts tested in the dehydrogenation of DMAB under mild
Copyright: American Scientific Publishers
conditions (≤25 ꢀC).
Entry
(Pre) catalysts
Conv. (%)
TOF
Ref
4. CONCLUSIONS
1
2
3
4
5
6
7
8
Pt NPs
100
77
97
70
100
20
100
100
100
95
100
97
21ꢃ5 This study
RuCl3 ·3H2O
2ꢃ7
13ꢃ4
2ꢃ5
[41]
[40]
[41]
[27]
[34]
[34]
[39]
[27]
[34]
[34]
[40]
[27]
[34]
[34]
[36]
[38]
[34]
[33]
[34]
[34]
[34]
[34]
[34]
[34]
[42]
[34]
[41]
In the current work, highly efficient and active nearly
monodisperse Pt NPs have been prepared, characterized
and used as a heterogeneous catalyst for both C1 to C3
alcohol oxidation and DMAB dehydrogenation reaction.
Some of the fundamental findings of this study are sum-
marized below:
[Cr(CO)5(thf)]
[Ru(1,5-cod)Cl2 ]n
Rh(0)NPs
60ꢃ0
0ꢃ2
2ꢃ6
trans-PdCl2 (P(o-tolyl)3 ꢆ2
[RhCl(PHCy2 ꢆ3]
(Idipp)CuCl
Ru(0)/APTS
Pd/C
[Cp*Rh(m-Cl)Cl]2
[Cr(CO)5(h1-BH3NMe3ꢆ]
Ru(cod)(cot)
HRh(CO)(PPh3ꢆ3
[Rh(1,5-cod)m-Cl]2
Cp2Ti
[RuH(PMe3ꢆ(NC2H4PPr2ꢆ2]
IrCl3
[(C5H3-1,3(SiMe3ꢆ2ꢆ2Ti]2
Rh(0)/[Noct4 ]Cl
RhCl(PPh3 ꢆ3
0ꢃ3
55ꢃ0
2ꢃ8
9
•
Nearly monodisperse Pt NPs have been prepared by
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
using a simple and reproducible superhydride reduction
method in an ultrasonic sonicator. The ICP-OES, XRD,
XPS, TEM, AFM characterizations of these nanoparticles
confirmed the formation of well-dispersed Pt(0) nanopar-
ticles supported on activated carbon.
0ꢃ9
19ꢃ9
1ꢃ6
40
5
0ꢃ1
100
100
100
25
100
90
100
95
95
12ꢃ5
12ꢃ3
1ꢃ5
•
Pt NPs provide one of the highest catalytic activities
(TOF = 21.50 h−1) found in the literature in the dehy-
drogenation of DMAB at room temperature. The catalyst
developed in this study was also recoverable and reusable,
retaining ≥80% of the initial activity after four runs. The
used capping ligand provided exceptional stability against
clumping and leaching throughout the catalytic dehydro-
genation of DMAB.
0ꢃ3
420ꢃ0
8ꢃ2
4ꢃ3
1ꢃ7
0ꢃ7
[Rh(1,5-cod)(dmpe)]PF6
[Ir(1,5-cod)m-Cl]2
[Rh(1,5-cod)2 ]Otf
trans-RuMe2 (PMe3ꢆ4
Ni(skeletal)
95
12ꢃ0
12ꢃ4
3ꢃ2
100
100
90
•
The dehydrogenation of DMAB using Pt NPs was car-
ried out at different temperatures to examine the acti-
RhCl3
Pt(0)/AA
7ꢃ9
15ꢃ0
100
vation parameters (Ea, ꢋH=, ꢋS=). We found that Pt
J. Nanosci. Nanotechnol. 16, 5944–5950, 2016
5949

Synthesis and Characterization of Nearly Monodisperse Pt Nanoparticles
Erken et al.
NPs provide one of the lowest activation energies (Ea =
48.36 kJ/mol) reported among the heterogeneous cata-
lysts tested in the same reaction. The activation enthalpy
16. R. Parsons and T. Vander Noot, J. Electroanal Chem. 9, 257 (1988).
17. T. Iwasita, Electrochim. Acta 47, 3663 (2002).
18. G. Andreadis, S. Song, and P. Tsiakaras, J. Power Sources 157, 657
(2006).
19. J. Wang, S. Wasmus, and R. F. Savinell, J. Electrochem. Soc.
142, 4218 (1995).
20. V. Galvita, G. Semin, V. Belyaev, V. Semikolenov, P. Tsiakaras, and
V. Sobyanin, Appl. Catal. A. 220, 123 (2001).
21. S. Song, W. Zhou, Z. Liang, R. Cai, G. Sun, Q. Xin,
V. Stergiopoulos, and P. Tsiakaras, Appl. Catal. B: Environ. 55, 65
(2005).
22. Z. Qi and A. Kaufman, J. Power Sources 118, 54 (2003).
23. F. Sen, G. Gökag˘aç, and S. Sen, J. Nanopart. Res. 15, 1979 (2013).
24. F. Vigier, S. Rousseau, C. Coutanceau, J. M. Leger, and C. Lamy,
Top Catal. 40, 1 (2006).
(ꢋH= = 45ꢃ82 kJ/mol) and activation entropy (ꢋS=
=
−112ꢃ99 J/mol K) values calculated from the Eyring plots
suggest an associative mechanism for the Pt NPs dehydro-
genation of DMAB.
With the advantages in the ease of synthesis, rela-
tively high activities, catalytic versatility, efficient recov-
ery, and prolonged stability and reusability, Pt NPs offer
a promising approach towards realizing a commercially
viable technology using DMAB as a CO-free, H2 storage
and generation system for fuel cell applications.
25. S. P. Jiang, Z. Liu, H. L. Tang, and M. Pan, Electrochim. Acta
51, 5721 (2006).
26. Z. B. Wang, G. P. Yin, and P. F. Shi, J. Electrochem. Soc. 152, A2406
(2005).
27. V. S. Bogotzky and Y. B. Vassilyev, Electrochim. Acta 12, 1323
(1967).
Acknowledgments: The authors would like to thank
Dumlupinar University (DPU-2014-5) and Duzce Univer-
sity (DUBAP-2014.05.03.243) for the financial support.
28. F. Kadirgan, S. Beyhan, and T. Atilan, Int. J. Hyd. Ener. 34, 4312
(2009).
29. S. Özkar and R. G. Finke, J. Am. Chem. Soc. 124, 5796 (2002).
30. K. J. Laidler, Chemical Kinetics, 3rd edn., Benjamin-Cummings, UK
(1997).
31. H. Eyring, J. Chem. Phys. 3, 107 (1935).
32. Y. Sun, L. Zhuang, J. Lu, X. Hong, and P. Liu, J. Am. Chem. Soc.
129, 15465 (2007).
33. D. Pun, E. Lobkovsky, and P. Chirik, J. Chem. Commun. 44, 3297
(2007).
References and Notes
1. C. Lamy, J.-M. Leꢂger, and S. Srinivasan, Kluwer Academic/Plenum
Publishers, New York (2001), Vol. 34, pp. 53–118.
2. F. Sen, S. Ertan, S. Sen, and G. Gokagac, J. Nanopart. Res. 14, 922
(2012).
3. F. Sen, Z. Ozturk, S. Sen, and G. Gokagac, J. Mater. Sci. 47, 8134
(2012).
4. S. Sen, F. Sen, and G. Gökag˘aç, Phys. Chem. Chem. Phys. 13, 1676
(2011).
34. C. A. Jaska, K. Temple, A. J. Lough, and I. Manners, J. Am.Chem.
5. S. Sen, F. Sen, and G. Gökag˘aç, Phys. DCheelmiv. eCrheemd.bPyhyIsn. 1g3e, n67ta84to: University of Auckland
IP: 5.101.217.13 On: Sun,3055. SPJ.ouTcn.. 1A22.50S,u19m64o20d4j1o(2,:02E0.43J:).4.S9ilva, and T. Rabochai, J. Electroanal. Chem.
(2011).
Copyright: American Scientific Publishers
6. L. Carrette, K. A. Fiedrich, and U. Stimming, Fuel Cells 1, 5 (2001).
7. F. Sen and G. Gökag˘aç, J. Phys. Chem. C 111, 1467 (2007).
8. F. Sen and G. Gökag˘aç, Energy and Fuels 22, 1858 (2008).
9. F. Sen and G. Gökag˘aç, J. Phys. Chem. C 111, 5715 (2007).
10. F. Sen and G. Gökag˘aç, J. Appl. Electrochem. 44, 199 (2014).
11. X. Ren, M.S. Wilson, and S. Gottesfeld, J. Electrochem. Soc. 143, 12
(1996).
12. L. Liu, C. Pu, R. Viswanathan, Q. Fan, R. Liu, E. S. Smotkin, Elec-
trochim Acta 43, 3657 (1998).
13. M. P. Hogarth and G. A. Hards, Platinum Met. Rev. 40, 150 (1996).
14. B. D. McNicol, D. A. J. Rand, and K. R. Williams, J. Power Sources
83, 15 (1999).
271, 305 (1989).
36. T. J. Clark, C. A. Russell, and I. Manners, J. Am. Chem. Soc.
128, 9582 (2006).
37. M. Sloan, T. J. Clark, and I. Manners, Inorg. Chem. 48, 2429 (2009).
38. A. Friendrich, M. Drees, and S. Schneider, J. Chem.-Eur. 15, 10339
(2009).
39. R. J. Keaton, J. M. Blacquiere, and R. T. Baker, J. Am. Chem. Soc.
129, 11936 (2007).
40. Y. Kawano, M. Uruichi, M. Shiomi, S. Taki, T. Kawaguchi,
T. Kakizawa, and H. Ogino, J. Am. Chem. Soc. 131, 14946 (2009).
41. F. Sen, Y. Karatas, M. Gulcan, and M. Zahmakiran, RSC Adv. 4, 1526
(2014).
15. C. Korzeniewski and C. L. Childers, J. Phys. Chem. 102, L489
(1998).
42. A. P. M. Robertson, R. Suter, L. Chabanne, G. R. Whittel,
I. Manners, Inorg. Chem. 50, 12680 (2011).
Received: 30 March 2014. Accepted: 22 April 2015.
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