A simple and effective route for preparation of platinum nanoparticle and its application for electrocatalytic oxidation of methanol and formaldehyde

Article abstract of DOI:10.1016/j.molliq.2015.10.031

In this work, a new and facile method for preparation of platinum nanoparticles (Pt-NPs) at the surface of glassy carbon electrode (GCE) is reported. Firstly, nickel nanoparticles (Ni-NPs) as sacrificial templates are uniformly electrodeposited onto the GCE by using potentiostatic method at a fixed potential (- 1.0 V vs. Ag|AgCl|KCl (3 M)) in 0.5 M H₂SO₄ solution. Then, Pt-NPs are prepared through a spontaneous and irreversible process via galvanic replacement reaction (GRR) between PtCl₆^{2 -} and Ni-NPs. The obtained results indicate that the Ni-NPs are completely replaced with Pt-NPs in acid solution. The obtained results from cyclic voltammetry and chronoamperometry reveal that the Pt-NPs demonstrate an enhanced electrocatalytic activity for methanol and formaldehyde oxidation. The effect of several parameters such as electrodepositing potential, NiSO₄ concentration, electrodeposition and GRR time for methanol oxidation as well as stability of the modified electrode has been investigated.

Full text of DOI:10.1016/j.molliq.2015.10.031

Journal of Molecular Liquids 212 (2015) 767–774
Contents lists available at ScienceDirect
Journal of Molecular Liquids
journal homepage: www.elsevier.com/locate/molliq
A simple and effective route for preparation of platinum nanoparticle and
its application for electrocatalytic oxidation of methanol
and formaldehyde
a,
b
a
Jahan-Bakhsh Raoof ⁎, Sayed Reza Hosseini , Sharifeh Rezaee
a
Electroanalytical Research Laboratory, Department of Analytical Chemistry, Faculty of Chemistry, University of Mazandaran, 47416-95447 Babolsar, Iran
Nanochemistry Research Laboratory, Faculty of Chemistry, University of Mazandaran, 47416-95447 Babolsar, Iran
b
a r t i c l e i n f o
a b s t r a c t
Article history:
In this work, a new and facile method for preparation of platinum nanoparticles (Pt-NPs) at the surface of glassy
carbon electrode (GCE) is reported. Firstly, nickel nanoparticles (Ni-NPs) as sacrificial templates are uniformly
electrodeposited onto the GCE by using potentiostatic method at a fixed potential (−1.0 V vs. Ag│AgCl│KCl
Received 28 March 2015
Received in revised form 29 September 2015
Accepted 16 October 2015
Available online xxxx
(
3 M)) in 0.5 M H
2 4
SO solution. Then, Pt-NPs are prepared through a spontaneous and irreversible process via
2
−
galvanic replacement reaction (GRR) between PtCl
6
and Ni-NPs. The obtained results indicate that the
Ni-NPs are completely replaced with Pt-NPs in acid solution. The obtained results from cyclic voltammetry and
chronoamperometry reveal that the Pt-NPs demonstrate an enhanced electrocatalytic activity for methanol
and formaldehyde oxidation. The effect of several parameters such as electrodepositing potential, NiSO concen-
4
Keywords:
Galvanic replacement reaction
Nickel nanoparticle
Platinum nanoparticle
Electrocatalytic oxidation
tration, electrodeposition and GRR time for methanol oxidation as well as stability of the modified electrode has
been investigated.
©
2015 Elsevier B.V. All rights reserved.
1
. Introduction
convenient route was widely used for the synthesis of metal NPs by
applying particles of various transition metals such as Ni, Cu, Fe, and
Co [10,11]. This method has attracted much attention due to its simplic-
ity of operation, cost effectiveness and simple equipment. The GRR is a
single step and irreversible reaction which is reliant on the difference
in standard electrode potentials of the various elements [12]. The spon-
taneous reaction occurs between the solid metal (i.e., template) and
ions of a second metal having higher electrode potential which leads
to the deposition of more noble elements and dissolution of the less
noble components.
To date, among the different transition metal particles, platinum (Pt)
due to its unique physical and chemical characteristics, including high
durability and specific activity is quite noticeable from others as
electrocatalyst [1,2]. However, the high cost and limited supply of Pt
are limiting factors. So, the use of Pt particles at nano-scale by control-
ling the morphology and surface structure is an effective way to reduce
the amount of the required Pt and enhance the electrochemical activity
[3,4]. Since, catalysis is a surface phenomenon; Pt particles with small
sizes demonstrate high activity and display excellent resistance against
poisoning effect by COads species, which are formed during the metha-
nol oxidation. Formation of multiple Pt-carbon bonds is less at Pt parti-
cles with small sizes, in comparison with bulk Pt [5,6]. So, researches
have been focused on the exploration of novel synthetic routes to pre-
pare ultrafine nanostructured Pt catalysts.
So far, most studies have been focused on the diverse physical and
chemical methods for fabrication of fine noble metal nanoparticles [7].
By considering the potential preparation methods for production of
the metal NPs, one of the most plausible ways is metal exchange reac-
tion [8,9]. Galvanic replacement reaction (GRR) as one of typical and
Until now, many works have been made towards the synthesis of Pt
nanoparticles (Pt-NPs) or designing of Pt-based bimetallic catalysts and
Pt nano-materials with different shapes such as nano-cages, nano-tubes
and nano-porous films by GRR with different active metals. For exam-
ple, Qiu et al. [13] fabricated bimetallic Pt–Au thin films with different
Pt/Au ratios by GRR with hierarchical Co thin film. Kuang et al. [14]
synthesized hollow Pt nano-spheres/carbon nanotube nano-hybrids
by using silver NPs. Also, Tegou et al. [15] prepared mixed Pt/Au
by GRR with Ni layers. Mohl et al. [16] prepared CuPd and CuPt bi-
metallic nanotubes by using Cu, Pt and Pd. Xie et al. [17] synthesized
Pd@M
x
Cu1 − x (M = Au, Pd and Pt) nano-cages with porous walls
and a yolk–shell structure through the GRR. Bansal et al. [18] pre-
pared Ni–Cu nano-porous surface for catalysis by the GRR.
Recently, we have made Cu–Pt bimetallic NPs at the surface of poly
(8-hydroxyquinoline) film by using Cu as sacrificial and Pt as second
⁎
Corresponding author.
E-mail address: j.raoof@umz.ac.ir (J.-B. Raoof).
http://dx.doi.org/10.1016/j.molliq.2015.10.031
167-7322/© 2015 Elsevier B.V. All rights reserved.
0

768
J.-B. Raoof et al. / Journal of Molecular Liquids 212 (2015) 767–774
metal [19]. Our literature survey indicates that the fabrication of the Pt-
NP modified GCE (Pt-NP/MGCE) by using Ni nanoparticles (Ni-NPs) as
sacrificial templates has not been reported. Hence, in the present in-
vestigation, at first the Ni-NP electrodepositing was performed onto
the GCE surface and Pt-NPs were then prepared by GRR and their ef-
ficiency towards the electrocatalytic oxidation of methanol was in-
vestigated. The experimental data reveal that the Pt-NP/MGCE
showed excellent performance in the methanol oxidation and formal-
dehyde oxidation.
the surface into the electrolyte solution. Also, in the meantime, PtIV is re-
duced and deposited on the electrode surface. It should be noted that
during the GRR, Ni-NPs are dissolved into the solution via a reaction be-
+
tween Ni-NPs with H as a competitive reaction (4):
2−
0
2þ
−
2
NiðsÞ þ PtCl6 ðaqÞ→Pt þ 2Ni
þ 6Cl
ð3Þ
ð4Þ
ðsÞ
ðaqÞ
ðaqÞ
þ
2þ
Ni þ 2H →Ni
ðsÞ
þ H ðgÞ:
2
ðaqÞ
ðaqÞ
It is obvious that the displacing metal in comparison with sacrificial
metal manifests oxidation state (4:2). So, according to stoichiometry of
the redox reaction, during the reaction by deposition of a Pt atom at the
electrode surface, two Ni atoms leach in the surrounding aqueous envi-
ronment. Hence, on the basis of both reactions (3 and 4), all deposited
Ni-NPs release from the electrode surface. Afterwards, when the
2
. Experimental
2
.1. Reagents and materials
NiSO
4
·6H
2
O (99%, Fluka) was used in the preparation of Ni depo-
PtCl ·6H O (Merck) and NaOH (99%, Merck) were
sition solution. H
2
6
2
Pt-NP/MGCE was prepared, it was removed and rinsed with distilled
used as received. Methanol and formaldehyde from Merck were of
analytical grade. Sulfuric acid (98%, Fluka) was used for the prepara-
tion of the supporting electrolyte. K Fe(CN) , K Fe(CN) (99%, Fluka)
3 6 4 6
and KCl (99%, Merck) were used for impedance studies. The solvent
used in this work for preparation of the samples was double distilled
water.
2
water. The geometric surface area (A
g
= 0.018 cm ) was used to calcu-
late the current density, except for the comparison of the methanol ox-
idation and formaldehyde oxidation. All experiments were performed
at ambient temperature.
3. Results and discussion
2
.2. Electrochemical measurements
3.1. Electrochemical properties of the modified electrodes
The electrochemical experiments were carried out by using a
In order to ascertain the electrochemical response of the prepared
potentiostat/galvanostat (SAMA 500-C Electrochemical analysis
system, Sama, Iran) coupled with a personal computer (PC). Elec-
trochemical impedance spectroscopy (EIS) was performed by an
Autolab model PGSTAT 30 with FRA software version 4.9 (Eco
Chemie, The Netherlands). The three-electrode system consists of
the GCE (1.5 mm in diameter) as working electrode substrate,
Ag│AgCl│KCl (3 M) as reference electrode and a Pt wire as an auxiliary
electrode. The surface morphology and elemental analysis of the de-
posits were evaluated by scanning electron microscopy (SEM, model
VEGA-Tescan, Razi Metallurgical Research Center, Tehran, Iran)
equipped with an energy dispersive spectrometer (EDS).
modified electrode, after accomplishing Ni-NP electrodeposition, the
Ni-NP/MGCE was thoroughly rinsed with distilled water and 15 poten-
tial cycles were conducted between 0.2 and 0.8 V in 0.1 M NaOH
solution until stable cyclic voltammogram was obtained (Fig. 1A
2
.3. Preparation of the Ni nanoparticles
Prior to surface modification, the GCE was carefully polished with
polishing cloth and alumina slurry until a mirror finish was obtained.
To remove the alumina residues that might be trapped at the surface,
the polished electrode was placed in ethanol and sonicated for 5 min.
Then, the electrode was rinsed thoroughly with distilled water. After
that, Ni-NPs were electrodeposited potentiostatically at −1.0 V vs.
Ag│AgCl│KCl (3 M) for 500 s in 0.5 M H
2 4
SO solution containing
0
.5 M NiSO according to reaction (1). Also, associated with deposition
4
of Ni-NPs, hydrogen bubbles were released via hydrogen evolution re-
action as a competitive reaction according to reaction (2).
2
þ
þ 2e−→NiðsÞ
þ 2e−→H2ðgÞ:
Ni
ð1Þ
ð2Þ
ðaqÞ
þ
2
H
ðaqÞ
2
.4. Preparation of the Pt-NP/MGCE
After Ni-NP electrodeposition, the electrode was immediately im-
mersed in 0.5 M H SO solution containing 5.0 mM H PtCl for 20 min
to let GRR between Ni and Pt ions proceeds. Since, the standard re-
2
4
0
2
6
IV
IV
0
duction potential of the Pt /Pt pair (+0.73 V vs. SHE) is higher than
Fig. 1. (A) 15th CV signal of the Ni-NP/MGCE in 0.1 M NaOH (solid line) and 0.5 M H
2
SO
SO
4
the Ni2+/Ni pair (−0.25 V vs. SHE), Ni-NPs can be oxidized by PtCl
0
2−
−1
6
solution (dotted line) at υ = 50 mV s . (B) CV signal of the Pt-NP/MGCE in 0.5 M H
2
4
solution at υ = 50 mV s−
1
.
according to following replacement reaction (3) and removed from

J.-B. Raoof et al. / Journal of Molecular Liquids 212 (2015) 767–774
769
(
solid line)). Consecutive cyclic voltammetry (CV) leads to the pro-
there is a reasonable explanation. The interpretation says that since
the appearance of the H3rd is closely related to the start of hydrogen
evolution, it can be concluded that the third anodic peak is attributed
to oxidation of adsorbed molecular hydrogen which may be the in-
termediate in hydrogen evolution. This reaction is a slow process
and one reasonable cause for this observation can be due to that the mo-
lecular hydrogen is sub-surface adsorbed and forms possibly on Pt
(110) sites with surface structure, produced by oxidation–reduction
cycles. So, forming partial amount of Pt (110) sites with surface struc-
ture on a platinized Pt surface presented insignificant and poor current
of the H3rd [22].
gressive growth of anodic and cathodic peak current density. As
can be seen in this figure, the electrochemical response of the
Ni-NP/MGCE exhibited well-defined anodic and cathodic peaks
(
Ni(III)/Ni(II) redox couple). The redox peak is ascribable to the ox-
idation of Ni(OH) to NiOOH (0.42 V) and reduction of the NiOOH
to Ni(OH) (0.38 V). The redox process is expressed by the following
reaction [20].
2
2
−
−
NiðOHÞ þ OH →NiOOH þ H2O þ e :
ð5Þ
2
It should be noted that the Ni-NP/MGCE was not stable in acidic me-
dium and when it was placed in 0.5 M H SO solution Ni-NPs were re-
moved/dissolved from the electrode surface into the solution. According
to this reason, the Ni-NP/MGCE has no electrochemical response/
The peak current of Pt oxide reduction in 0.5 M H SO solution was
2
4
2
4
;
used for evaluation of the Pt loading at the Pt-NP/MGCE by faradaic
−
2
law and was estimated at about 1.85 μg cm . Furthermore, real surface
area (A ) of the Pt catalyst can be measured according to the following
r
activity in H
ous, the electrochemical response of the Pt-NPs was studied in a
potential window of −0.3 to 1.0 V in 0.5 M H SO solution and
the typical CV signal was presented in Fig. 1B. The whole of CV signal
can be readily separated in five potential regions. These typical peaks
can be explained as following as: in the lower potential range (I) HER,
2
SO
4
solution (Fig. 1A (dotted line)). Also, in continu-
equation:
2
4
Ar ¼ Q =QO
ð6Þ
H
H
where Q is the charge consumed for hydrogen adsorption and can be
(
(
II) weakly bonded hydrogen (H
w
), (III) strongly bonded hydrogen
obtained by integrating in the hydrogen adsorption/desorption region.
2
H
s
) and furthermore in positive potential range (IV) corresponding
Also, Q
O r
has been commonly taken as 210 μC/real cm . The A was ob-
2
to the formation and reduction of Pt oxide and potential region (V) is
attributed to double layer [21]. Moreover, there is a negligible peak
similar to bump between the peaks (I) and (II). According to literature,
tained at about 0.71 cm . Also, the roughness factor can be obtained
r g
by dividing of A to A . Hence, the value of the calculated RF is equal to
39.7.
Fig. 2. SEM images of the prepared Ni-NP/MGCE (a, b) and Pt-NP/MGCE (c, d).

770
J.-B. Raoof et al. / Journal of Molecular Liquids 212 (2015) 767–774
3
.2. Surface morphology and elemental analysis
In order to characterize the prepared electrodes, micrographs of the
Ni-NP/MGCE (a, b) and Pt-NP/MGCE (c,d) were investigated by SEM
Fig. 2). Traces (a, b) show that the Ni-NPs with spherical shapes were
(
distributed in the form of extended coverage over a large area on the
GCE surface. As shown in trace (c, d), the Pt-NPs can be generated by
using complete GRR of the Ni-NPs by Pt-NPs. The Pt-NPs with granular
structure and spherical shapes and average sizes at about 80 nm were
uniformly spread on the GCE.
Fig. 3 presented a typical EDS spectrum for determination of the
electrode composition. The EDS gives evidences for the presence of
the Ni and Pt in the modified electrode. As can be seen in this figure,
Pt and Ni in the modified electrodes are the major elements and C is de-
rived from the GCE. Also, by comparison with (A) and (B), it can be seen
that the EDS data are in accordance with obtained results from the SEM.
The results reveal that the Ni-NPs are completely replaced with Pt-NPs
and no Ni-NPs remain at the final modified electrode. It should be
noted that the reason of Au existence is that the specimens are usually
coated with an ultra-thin coating of Au before measurements.
Fig. 4. Nyquist plots of impedance measurements of 1.0 mM K
3 6 4 6
[Fe(CN) ] / K [Fe(CN) ] +
0.1 M KCl on bare GCE (a) and Pt-NP/MGCE (b).
3
.3. EIS investigation
Nyquist diagrams of the bare GCE (a) and Pt-NP/MGCE (b) in the pres-
ence of 1.0 mM K [Fe(CN) ] / K [Fe(CN) ] (1:1) + 0.1 M KCl solution. As
EIS is an effective and simple way for evaluating the interface prop-
3
6
4
6
erties of the modified electrodes [23]. All impedance spectra are almost
similar in form, composed of a high-frequency semicircle and a low-
frequency straight line. The diameter of the semicircle is assigned to
the interfacial charge transfer resistance (Rct) and a straight line is
attributed to the diffusion-limited process [24]. Fig. 4 presented the
can be seen in this figure, there is an obvious difference between the di-
ameters of two semicircles. The Pt-NP/MGCE has a very small semicircle
domain, implying a much lower Rct than the bare GCE. There are more
active sites for easier charge transfer and faradaic reactions at the inter-
face owing to the presence of Pt-NPs.
3.4. Electrocatalytic oxidation of methanol
Fig. 5 depicted the CV signals of the methanol oxidation onto the Ni-
NP/MGCE (a) and Pt-NP/MGCE (b) in 0.5 M H SO + 1.36 M CH OH so-
2 4 3
lution. As can be seen in this figure, the inactivity of the Ni-NP/MGCE for
methanol oxidation is in accordance with the observation that Ni-NPs
2 4
are not stable in H SO medium. Methanol electrooxidation at the Pt
surface exhibited the characteristic double CV peaks which appear in
the forward and reverse scans [6]. It can be seen from methanol oxida-
tion on the Pt-NP/MGCE that the onset potential is at around 0.15 V and
an enormous anodic peak appears approximately at 0.73 V in forward
2
scan which is generated by oxidation of the COads to CO (I). The current
density was defined as current normalized per A and obtained about
r
Fig. 5. Electrochemical responses of the Ni-NP/MGCE (a) and Pt-NP/MGCE (b) in 1.36 M
3 2 4
CH OH + 0.5 M H SO .
solution at υ = 50 mV s−
1
Fig. 3. Energy dispersive spectra of the Ni-NP/MGCE (A) and Pt-NP/MGCE (B).

J.-B. Raoof et al. / Journal of Molecular Liquids 212 (2015) 767–774
771
Scheme 1. A schematic representation of methanol oxidation at the Pt-NP/MGCE.
1
.83 mA cm−2. After that, the oxidation peak current density decreases
4
−1.0 V, NiSO concentration up to 0.5 M, electrodeposition time up to
at more positive potential due to the formation of Pt oxides which pas-
sives the Pt surface. When the potential scan is reversed, the reduction
of the Pt oxide to Pt takes place and clean Pt is available at the surface.
Since, the methanol oxidation occurs more easily at the clean Pt surface,
therefore the peak current II appears at about 0.53 V in the backward
500 s and GRR time up to 20 min and drop afterwards.
3.6. Electrocatalytic oxidation of formaldehyde
Formaldehyde has become more interesting with the possibility of
its application in liquid fuel cells. The reasons are related to its facility
of handling, storage and generally high energy density. The electro-
chemical oxidation of formaldehyde is important for full under-
standing of methanol oxidation as a product of partial oxidation of
methanol [35,36]. Fig. 6 illustrates the CV signals of the Ni-NP/
MGCE (a) and Pt-NP/MGCE (b) in 0.5 M H SO + 0.32 M formalde-
scan which is attributed to the complete oxidation of CH
II) [25].
The electrochemical oxidation of methanol was schematically
3 2
OH to CO
(
shown in Scheme 1. The important advantage of the Pt particles
with nanoscale sizes is high activity and excellent resistance against
poisoning effect by COads species, which are formed during the meth-
anol oxidation. This phenomenon is the most important difference of
Pt-NPs in comparison with bulk Pt in acid medium. For evaluation of
the electrocatalytic activity in methanol oxidation, the onset poten-
tial was listed in Table 1 and compared with the some previous
works.
2
4
hyde. The observation indicates that the Ni-NPs are not stable in
0.5 M H SO solution. Hence, Ni-NP/MGCE gave no signal for formal-
2
4
dehyde oxidation and this indicates that the electrode has no elec-
trocatalytic activity and acts similar to the bare GCE (Fig. 6a). As
can be seen from trace (b), formaldehyde oxidation at the Pt-NP/
MGCE starts at about 0.25 V with low current and by sweeping to
more positive potentials, the peak current reaches to a maximum
3
.5. Parameters affecting the electrode modification
at about 0.65 V which is assigned to the oxidation of COads to CO
2
In order to evaluate the effect of various parameters such as electro-
(peak I) [37]. After that, the oxidation peak current decreases at
more positive potentials due to the formation of the Pt oxide which
causes passivity of the Pt surface. When the potential scan is re-
versed, the reduction of Pt oxides to Pt take place and clean Pt is
available. So, a large anodic peak is observed at about 0.4 V (peak II).
This peak is attributed to the complete oxidation of formaldehyde to
depositing potential, Ni2 concentration, electrodeposition and GRR
times on the methanol oxidation, the amount of peak current density
was monitored as an index for finding the optimum conditions and
the obtained results were summarized in Table 2. The results indicate
that the peak current increases for electrodepositing potential up to
+
CO
2
[38].
It was well accepted that the electrooxidation of formaldehyde on
Table 1
Comparison of methanol oxidation in H
modified electrodes.
2
SO
4
solution at the Pt/-NPs/MGCE with some
traditional Pt catalyst follows a dual parallel pathways. In the direct
Electrocatalyst
Pt nanorod/Tia
C
H SO4/M
C
CH OH/M
E
op/V
E
p
/V
Ref.
2
3
Table 2
0.5
1.0
0.5
0.5
0.1
1.0
0.1
0.2
1.0
0.5
2.0
2.0
1.4
0.5
0.05
2.0
0.5
0.15
2.0
1.36
0.36
0.22
0.20
0.20
0.15
0.26
0.15
0.15
0.45
0.15
0.61
0.89
0.7
0.62
0.53
0.75
0.88
0.89
0.64
0.73
[26]
[27]
[28]
[29]
[30]
[31]
[32]
[33]
Effect of several parameters on the peak current density of methanol oxidation in 0.5 M
a
Pt-NP/SWCNT
Nano-Pt/MGCE
H SO
2 4
+ 0.82 M CH
3
OH.
a
a
Pt/MGCE
E
d
/V
−0.9
2.83
0.1
6.74
100
7.86
10
15.50
−1.0
6.74
0.3
12.88
300
20.44
15
35.38
−1.1
5.33
0.5
20.44
500
35.38
20
47.22
−1.2
3.65
0.8
14.55
700
28.55
25
38.5
−1.3
1.35
1.0
10.26
900
16.11
30
24.33
a
−2
−2
−2
Pt/SBA-15/MGCE
j/mA cm
b
PtRu/MWCNT
C
NiSO4/M
a
PtNi/CCE
j/mA cm
/s
j/mA cm
/min
j/mA cm
b
Pt/CCE
t
d
a
Pt/SWCNT
[34]
This work
b
Pt-NP/MGCE
t
r
−
2
All potentials were referred to the (a) SCE and (b) Ag│AgCl│KCl (3 M).

772
J.-B. Raoof et al. / Journal of Molecular Liquids 212 (2015) 767–774
surface (dehydration pathway, Scheme 2). The poisonous COads are
removed via a reaction involving OHads species originated from
water dissociation. Indeed, this process is very intricate, as higher
potentials are required for water activation on the Pt surface [41].
Therefore, the electrode surface will be blocked by large amounts of
COads and inhibit further adsorption of the other formaldehyde mole-
cules. The important advantage of the Pt particles with nanoscale sizes
is higher activity and superior resistance against poisoning effect by
COads species.
For evaluation the electrocatalytic activity, the onset oxida-
tion potential and peak potential were listed in Table 3 and
electrooxidation herein has been compared with some previous
works.
3.7. Stability study
For further evaluation of the catalytic activity and catalyst stabil-
ity, chronoamperometric response of the Pt-NP/MGCE was recorded
at peak potential values in continuous operation for methanol and
formaldehyde (Fig. 7). As can be seen in this figure, current density
has slightly changed and decreases gradually with time passing.
The observed data reveal that the Pt-NP/MGCE has good poisoning
tolerance against generated intermediates due to the Pt NPs and
their fine dispersions. The Pt-NPs with small diameters provide
more active sites and accessible surface area for methanol oxidation
and formaldehyde oxidation.
Fig. 6. CV signals of the Ni-NP/MGCE (a) and Pt-NP/MGCE (b) in 0.32 M HCHO + 0.5 M
−
1
H SO
2 4
solution at υ = 50 mV s
.
route, formaldehyde is converted to CO
dehydrogenation pathway, Scheme 2) [39,40]. In the indirect path,
formaldehyde is oxidized to COads which is adsorbed on the Pt
2
via short-lived intermediate
(
Scheme 2. Schematic representation of formaldehyde oxidation on the Pt-NP/MGCE.
Table 3
Comparison of electrocatalytic oxidation of formaldehyde at the Pt-NP/MGCE with some modified electrodes at υ = 50 mV s−1.
Modified electrode
Electrolyte
0.5 M H
C
Formaldehyde (M)
E
op/V
E
p
/V
Ref.
Pt–Pd/CNT
Single crystal disk of Pt (111)
Pt–Pd/PPy-CNT
Pt/carbon–ceramic
Pt–Pd/Nf/MGCE
Pt/SWCNT/PANI
Pt/nano-PDAN/MGCE
Pt/PAANI/MWCNTs/MGCE
Pt-NP/MGCE
2
SO
4
0.50
0.50
0.50
0.75
0.001
0.26
0.26
0.50
0.32
0.30
0.20
0.20
0.20
0.30
0.30
0.20
0.20
0.29
0.62
0.70
0.64
0.85
0.58
0.66
0.75
0.72
0.69
[39]
[40]
[42]
[43]
[44]
[45]
[46]
[47]
0.1 M HClO
4
0.5 M H
0.1 M H
0.1 M H
0.5 M H
0.5 M H
0.5 M H
0.5 M H
2
2
2
2
2
2
2
SO
4
4
4
4
4
4
4
SO
SO
SO
SO
SO
SO
This work
All potentials were referred to SCE.

J.-B. Raoof et al. / Journal of Molecular Liquids 212 (2015) 767–774
773
[
[
8] C.L. Lee, C.M. Tseng, R.B. Wu, C.C. Wu, S.C. Syu, Catalytic characterization of hollow
silver/palladium nanoparticles synthesized by a displacement reaction, Electrochim.
Acta 54 (2009) 5544–5547.
9] C. Li, Y. Su, X. Lv, H. Shi, X. Yang, Y. Wang, Enhanced ethanol electrooxidation of
hollow Pd nanospheres prepared by galvanic exchange reactions, Mater. Lett. 69
(2012) 92–95.
[
10] S. Papadimitriou, A. Tegou, E. Pavlidou, S. Armyanov, E. Valova, G. Kokkinidis, S.
Sotiropoulos, Preparation and characterisation of platinum-and gold-coated copper,
iron, cobalt and nickel deposits on glassy carbon substrates, Electrochim. Acta 53
(2008) 6559–6567.
[
[
[
[
[
11] A. Tegou, S. Papadimitriou, S. Armyanov, E. Valova, G. Kokkinidis, S. Sotiropoulos,
Oxygen reduction at platinum-and gold-coated iron, cobalt, nickel and lead deposits
on glassy carbon substrates, J. Electroanal. Chem. 623 (2008) 187–196.
12] D. Gokcen, S.E. Bae, S.R. Brankovic, Reaction kinetics of metal deposition via surface
limited redox replacement of underpotentially deposited metal monolayers,
Electrochim. Acta 56 (2011) 5545–5553.
13] C. Qiu, Y. Guo, J. Zhang, H. Ma, Y. Cai, Bimetallic Pt–Au thin film electrocatalysts with
hierarchical structures for the oxidation of formic acid, Mater. Chem. Phys. 127
(2011) 484–488.
14] Y. Kuang, B. Wu, Y. Cui, Y. Yu, X. Zhang, J. Chen, Preparation of hollow platinum
nanospheres/carbon nanotubes nanohybrids and their improved stability for
electro-oxidation of methanol, Electrochim. Acta 56 (2011) 8645–8650.
15] A. Tegou, S. Armyanov, E. Valova, O. Steenhaut, A. Hubin, G. Kokkinidis, S.
Sotiropoulos, Mixed platinum–gold electrocatalysts for borohydride oxidation pre-
pared by the galvanic replacement of nickel deposits, J. Electroanal. Chem. 634
(2009) 104–110.
[
16] M. Mohl, D. Dobo, A. Kukovecz, Z. Konya, K. Kordas, J. Wei, P.M. Ajayan, Formation of
CuPd and CuPt bimetallic nanotubes by galvanic replacement reaction, Phys. Chem.
C 115 (2011) 9403–9409.
[
17] S. Xie, M. Jin, J. Tao, Y. Wang, Z. Xie, Y. Zhu, Y. Xia, Synthesis and characterization of
Pd@MxCu1 − X (M = Au, Pd, and Pt) nanocages with porous walls and a yolk–shell
structure through galvanic replacement reactions, Chem. Eur. J. 18 (2012) (14877-
14877).
[
[
[
[
18] V. Bansal, H. Jani, J.D. Plessis, P.J. Coloe, S.K. Bhargava, Galvanic replacement reaction
on metal films: a one-step approach to create nanoporous surfaces for catalysis, Adv.
Mater. 20 (2008) 717–723.
19] J.B. Raoof, R. Ojani, S.A. Esfeden, S.R. Nadimi, Fabrication of bimetallic Cu/Pt nanopar-
ticles modified glassy carbon electrode and its catalytic activity toward hydrogen
evolution reaction, Int. J. Hydrog. Energy 35 (2010) 3937–3944.
20] J.B. Raoof, R. Ojani, S. Abdi, S.R. Hosseini, Highly improved electrooxidation of form-
aldehyde on nickel/poly (o-toluidine)/Triton X-100 film modified carbon nanotube
paste electrode, Int. J. Hydrog. Energy 37 (2012) 2137–2146.
21] B. Habibi, M. Pournaghi-Azar, H. Razmi, H. Abdolmohammad-Zadeh, Electrochemi-
cal preparation of a novel, effective and low cast catalytic surface for hydrogen evo-
lution reaction, Int. J. Hydrog. Energy 33 (2008) 2668–2678.
Fig. 7. Chronoamperogram of the Pt-NP/MGCE at 0.5 M H
2
SO
4
solution in the presence of
= 0.65 V.
[
[
22] T. Frelink, W. Visscher, J. Van Veen, The third anodic hydrogen peak on platinum;
(
A) 1.36 M CH OH at E = 0.73 V and (B) 0.32 M formaldehyde at E
3
p
p
2
subsurface H adsorption, Electrochim. Acta 40 (1995) 545–549.
23] E. Katz, I. Willner, Probing biomolecular interactions at conductive and semiconductive
surfaces by impedance spectroscopy: routes to impedimetric immunosensors, DNA-
sensors, and enzyme biosensors, Electroanalysis 15 (2003) 913–947.
4
. Conclusion
In this work, we have proposed a simple and quick method for prep-
[
[
24] A. Tarola, D. Dini, E. Salatelli, F. Andreani, F. Decker, Electrochemical impedance
spectroscopy of poly alkyl terthiophenes, Electrochim. Acta 44 (1999) 4189–4193.
25] K. Nagashree, N. Raviraj, M. Ahmed, Carbon paste electrodes modified by Pt and Pt–
Ni microparticles dispersed in polyindole film for electrocatalytic oxidation of meth-
anol, Electrochim. Acta 55 (2010) 2629–2635.
aration of the nano-scale Pt particles via GRR with Ni-NPs. The obtained
results from SEM and EDS revealed the complete replacement between
sacrificial metal (Ni) and noble metal (Pt). The Pt-NP/MGCE was used
[
26] Y.B. He, G.R. Li, Z.L. Wang, Y.N. Ou, Y.X. Tong, Pt nanorods aggregates with enhanced
electrocatalytic activity toward methanol oxidation, J. Phys. Chem. C 114 (2010)
19175–19181.
2 4
for electrocatalytic oxidation of methanol and formaldehyde in H SO
solution. It was observed that the Pt-NP/MGCE was capable to catalyze
effectively these small organic molecules. The satisfactory activity is ex-
actly connected to the Pt nanostructures, which provides more active
sites and high accessible surface areas. The electrocatalysis is affected
by various parameters in the modification steps.
[27] D.J. Guo, H.L. Li, High dispersion and electrocatalytic properties of Pt nanoparticles
on SWNT bundles, J. Electroanal. Chem. 573 (2004) 197–202.
[
[
[
28] J.B. Raoof, R. Ojani, S.R. Hosseini, Electrochemical synthesis of a novel platinum nano-
structure on a glassy carbon electrode, and its application to the electrooxidation of
methanol, Microchim. Acta 180 (2013) 879–886.
29] T. Huang, R. Jiang, D. Zhang, J. Zhuang, W. Cai, A. Yu, AC impedance investigation of
plating potentials on the catalytic activities of Pt nanocatalysts for methanol
electrooxidation, J. Solid State Electrochem. 14 (2010) 101–107.
30] Z.F. Chen, Y.X. Jiang, Y. Wang, J.M. Xu, L.Y. Jin, S.G. Sun, Electrocatalytic oxidation of
carbon monoxide and methanol at Pt nanoparticles confined in SBA-15:
voltammetric and in situ infrared spectroscopic studies, J. Solid State Electrochem.
9 (2005) 363–370.
References
[
1] A. Kiani, S. Hatami, Fabrication of platinum coated nanoporous gold film electrode: a
nanostructured ultra low-platinum loading electrocatalyst for hydrogen evolution
reaction, Int. J. Hydrog. Energy 35 (2010) 5202–5209.
[31] L. Li, Y. Xing, Pt–Ru nanoparticles supported on carbon nanotubes as methanol fuel
cell catalysts, J. Phys. Chem. C 111 (2007) 2803–2808.
[
[
[
[
[
2] I.A. Pašti, N.M. Gavrilov, S.V. Mentus, Hydrogen adsorption on palladium and plati-
[32] B. Habibi, E. Dadashpour, Carbon-ceramic supported bimetallic Pt–Ni nanoparticles
as an electrocatalyst for electrooxidation of methanol and ethanol in acidic media,
Int. J. Hydrog. Energy 38 (2012) 5425–5434.
[33] H. Razmi, E. Habibi, H. Heidari, Electrocatalytic oxidation of methanol and ethanol at
carbon ceramic electrode modified with platinum nanoparticles, Electrochim. Acta
53 (2008) 8178–8185.
num overlayers, Adv. Phys. Chem. 2011 (2011) 1–8.
3] X. Ren, P. Zelenay, S. Thomas, J. Davey, S. Gottesfeld, Recent advances in direct
methanol fuel cells, J. Power Sources 86 (2000) 111–116.
4] Z. Wei, H. Guo, Z. Tang, Methanol electro-oxidation on platinum and platinum–tin
alloy catalysts dispersed on active carbon, J. Power Sources 58 (1996) 239–242.
5] E. Antolini, Composite materials: an emerging class of fuel cell catalyst supports,
Appl. Catal. B Environ. 100 (2010) 413–426.
6] J.B. Raoof, R. Ojani, S.R. Hosseini, Electrochemical fabrication of novel Pt/poly (m-to-
luidine)/Triton X-100 composite catalyst at the surface of carbon nanotube paste
electrode and its application for methanol oxidation, Int. J. Hydrog. Energy 36
[34] D.J. Guo, H.L. Li, Electrocatalytic oxidation of methanol on Pt modified single-walled
carbon nanotubes, J. Power Sources 160 (2006) 44–49.
[35] Z. Jing, X. Lin, Electrocatalytic oxidation of formaldehyde on copper oxide nano-
crystalline modified glassy carbon electrode, Chin. J. Chem. 28 (2010) 2359–2363.
[36] G. Samjeské, A. Miki, M. Osawa, Electrocatalytic oxidation of formaldehyde on plat-
inum under galvanostatic and potential sweep conditions studied by time-
resolved surface-enhanced infrared spectroscopy, J. Phys. Chem. C 111 (2007)
15074–15083.
(2011) 52–63.
[7] A. Chen, P. Holt-Hindle, Platinum-based nanostructured materials: synthesis, prop-
erties, and applications, Chem. Rev. 110 (2010) 3767–3804.

774
J.-B. Raoof et al. / Journal of Molecular Liquids 212 (2015) 767–774
[
[
[
37] P.J. Kulesza, M. Matczak, A. Wolkiewicz, B. Grzybowska, M. Galkowski, M.A. Malik, A.
Wieckowski, Electrocatalytic properties of conducting polymer based composite
film containing dispersed platinum microparticles towards oxidation of methanol,
Electrochim. Acta 44 (1999) 2131–2137.
38] L.H. Mascaro, D. Gonçalves, L.O.S. Bulhões, Electrocatalytic properties and
electrochemical stability of polyaniline and polyaniline modified with plati-
num nanoparticles in formaldehyde medium, Thin Solid Films 461 (2004)
of formic acid and formaldehyde for fuel cell applications, Appl. Catal. B Environ.
75 (2007) 129–138.
[43] B. Habibi, N. Delnavaz, Electrocatalytic oxidation of formic acid and formaldehyde
on platinum nanoparticles decorated carbon–ceramic substrate, Int. J. Hydrog.
Energy 35 (2010) 8831–8840.
[44] Z.L. Zhou, T.F. Kang, Y. Zhang, S.Y. Cheng, Electrochemical sensor for formaldehyde
based on Pt–Pd nanoparticles and a Nafion-modified glassy carbon electrode,
Microchim. Acta 164 (2009) 133–138.
[45] Z. Wang, Z.Z. Zhu, J. Shi, H.L. Li, Electrocatalytic oxidation of formaldehyde on plati-
num well-dispersed into single-wall carbon nanotube/polyaniline composite film,
Appl. Surf. Sci. 253 (2007) 8811–8817.
2
43–249.
39] V. Selvaraj, A.N. Grace, M. Alagar, Electrocatalytic oxidation of formic acid and form-
aldehyde on nanoparticle decorated single walled carbon nanotubes, J. Colloid Inter-
face Sci. 333 (2009) 254–262.
[
[
[
40] E. Batista, T. Iwasita, Adsorbed intermediates of formaldehyde oxidation and their
role in the reaction mechanism, Langmuir 22 (2006) 7912–7916.
4
41] T. Iwasita, X. Xia, Adsorption of water at Pt (111) electrode in HClO solutions, the
potential of zero charge, J. Electroanal. Chem. 411 (1996) 95–102.
42] V. Selvaraj, M. Alagar, K.S. Kumar, Synthesis and characterization of metal
[46] J.B. Raoof, R. Ojani, S.R. Hosseini, Electrocatalytic oxidation of methanol onto plati-
num particles decorated nanostructured poly (1,5-diaminonaphthalene) film, J.
Solid State Electrochem. 16 (2012) 2699–2708.
[47] C. Jiang, H. Chen, C. Yu, S. Zhang, B. Liu, J. Kong, Preparation of the Pt nanoparticles
decorated poly (N-acetylaniline)/MWNTs nanocomposite and its electrocatalytic
oxidation toward formaldehyde, Electrochim. Acta 54 (2009) 1134–1140.
nanoparticles-decorated PPY–CNT composite and their electrocatalytic oxidation