Electrochemical polymerization of pyrrole containing TEMPO side chain on pt electrode and its electrochemical activity

Article abstract of DOI:10.1016/j.electacta.2014.03.028

Poly(4-(3-(pyrrol-1-yl)propionyloxy)-2,2,6,6-tetramethylpiperidin-1-yloxy) (PPy-TEMPO) electrode is prepared by electrochemical polymerization on Pt electrode in NaClO₄-CH₃CN solution. The electrocatalytic activity of PPy-TEMPO for benzyl alcohol in NaClO₄-CH₃CN solution is investigated by cyclic voltammetry and in situ FTIR. Results show that PPy-TEMPO electrode exhibits high electrocatalytic activity for benzyl alcohol oxidation in the presence of 2,6-lutidine as the base, as compared with the bare Pt electrode under the similar conditions. On the basis of in situ FTIR data, it shows that TEMPO is oxidized to its cation at the potential about 0.4 V, and benzyl alcohol is oxidized to benzaldehyde instead of benzoic acid. Further studies of preparative electrolysis experiments by constant current electrolysis are carried out to confirm the high conversion to benzaldehyde, and the results are in good agreement with those from in situ FTIR investigations.

Full text of DOI:10.1016/j.electacta.2014.03.028

Electrochimica Acta 130 (2014) 412–417
Contents lists available at ScienceDirect
Electrochimica Acta
journal homepage: www.elsevier.com/locate/electacta
Electrochemical Polymerization of Pyrrole Containing TEMPO Side
Chain on Pt Electrode and Its Electrochemical Activity
Jin-jin Lua,b, Jia-qi Mab, Jing-miao Yia,b, Zhen-lu Shenb, Yi-jun Zhongc,∗∗, Chun-an Mab,
Mei-chao Lia,b,∗
a Research Center of Analysis and Measurement, Zhejiang University of Technology, Hangzhou 310032, Zhejiang, P. R. China
b College of Chemical Engineering and Materials Science, Zhejiang University of Technology, Hangzhou, 310032, Zhejiang, P. R. China
c Institute of Physical Chemistry, Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Zhejiang Normal University, Jinhua, 321004,
Zhejiang, P. R. China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 8 January 2014
Received in revised form 12 February 2014
Accepted 1 March 2014
Available online 16 March 2014
Poly(4-(3-(pyrrol-1-yl)propionyloxy)-2,2,6,6-tetramethylpiperidin-1-yloxy) (PPy-TEMPO) electrode is
prepared by electrochemical polymerization on Pt electrode in NaClO4-CH3CN solution. The electro-
catalytic activity of PPy-TEMPO for benzyl alcohol in NaClO4-CH3CN solution is investigated by cyclic
voltammetry and in situ FTIR. Results show that PPy-TEMPO electrode exhibits high electrocatalytic
activity for benzyl alcohol oxidation in the presence of 2,6-lutidine as the base, as compared with the
bare Pt electrode under the similar conditions. On the basis of in situ FTIR data, it shows that TEMPO is
oxidized to its cation at the potential about 0.4 V, and benzyl alcohol is oxidized to benzaldehyde instead
of benzoic acid. Further studies of preparative electrolysis experiments by constant current electrolysis
are carried out to confirm the high conversion to benzaldehyde, and the results are in good agreement
with those from in situ FTIR investigations.
Keywords:
TEMPO
Pyrrole
In situ FTIR
Benzyl alcohol
Benzaldehyde
© 2014 Elsevier Ltd. All rights reserved.
1. Introduction
immobilize TEMPO onto the electrode surfaces, such as organosilica
[10], poly(acrylic acid) [11] and poly(phenylene oxide) [12].
The selective oxidation of alcohols to the corresponding alde-
hydes or ketones is one of the important reactions in drugs, dyes
and fine chemicals [1]. Traditionally, such oxidation transforma-
tions have been performed with transition metals, e.g. Cr and Mn
salts, as stoichiometric inorganic oxidants [2,3]. From both eco-
nomic and environmental viewpoints, there is an urgent demand
to design clean, efficient and simple synthetic routes that employ
new types of catalytic materials instead of toxic oxidants.
With good ambient stability and electrochemical activity,
polypyrrole (PPy) is an important conducting polymer and has
been widely used in electrochemical area [13]. It is simple and
controllable for the electrode surface to be modified with PPy by
electrochemical polymerization [14]. Taking into consideration of
its easy preparation, the electrochemical polymerization is chosen
as a useful tool to prepare PPy containing TEMPO side chain on Pt
electrode. To have better insights of the process of alcohol oxida-
tion on the PPy-TEMPO electrode, voltammetry has been widely
used because of its high sensitivity, rapid response and simplicity.
However, without any additional information from other charac-
terization techniques, voltammetry are usually insufficient for a
full investigation of the reaction mechanism of the catalytic oxida-
tion of alcohol. In situ FTIR spectroscopy technique provides direct
spectroscopic information from very small amounts of material.
It is believed that it can serve as a powerful method to identify
the intermediates (such as cations or radicals) and products in the
electrochemical processes at a molecular level[15–17].
With low environmental contamination and high selectiv-
ity,
a stable nitroxyl radical such as 2,2,6,6-tetramethyl-1-
piperidinyloxyl (TEMPO) has attracted considerable attentions in
chemical industry [4–8]. Its active species (oxoammonium ions)
can be easily generated electrochemically by the one-electron oxi-
dation of TEMPO radical at a small electric potential, and they
are known to be employed as selective oxidizing agents of alco-
hols to form the corresponding aldehydes or ketones [9]. However,
TEMPO is rather expensive, which means separation and recycling
are important. Several groups have designed some materials to
Poly(4-(3-(pyrrol-1-yl)propionyloxy)-2,2,6,6-
tetramethylpiperidin-1-yloxy) (PPy-TEMPO) electrode is prepared
and benzyl alcohol is chosen as a model molecule of the alcohols in
this paper. The aims of our work are to: (i) prepare and characterize
the PPy-TEMPO film, (ii) investigate the electrocatalytic activity
∗
Corresponding author. Tel.: +86 571 88320568; fax: +86 571 88320961.
Corresponding author.
E-mail addresses: yjzhong@zjnu.cn (Y.-j. Zhong), limc@zjut.edu.cn (M.-c. Li).
∗∗
http://dx.doi.org/10.1016/j.electacta.2014.03.028
0013-4686/© 2014 Elsevier Ltd. All rights reserved.

J.-j. Lu et al. / Electrochimica Acta 130 (2014) 412–417
413
of the PPy-TEMPO electrode for oxidation of benzyl alcohol with
0.6
0.4
electrochemical methods, (iii) examine the reaction mechanism of
oxidation of benzyl alcohol on PPy-TEMPO electrode using in situ
FTIR technique.
0.2
2. Experimental
0.0
2.1. Synthesis of the monomer Py-TEMPO
-0.2
-0.4
-0.6
The
4-(3-(pyrrol-1-yl)propionyloxy)-2,2,6,6-tetramethylpi-
peridin-1-yloxy (Py-TEMPO) was synthesized according to the
procedures shown in Scheme 1. 3-(Pyrrol-1-yl)propanoic acid was
obtained as described in the literatures [18].
4-Hydroxy-TEMPO
propionic acid (7.0 g, 50.0 mmol) and
of 4-dimethylaminopyridine (DMAP) were stirred in 200 mL
of dichloromethane at 0 ◦C. Then
solution of N,N’-
dicyclohexylcarbodiimide (DCC, 10.3 g, 50.0 mmol) in
(8.6 g,
50.0 mmol),
3-(pyrrol-1-yl)
small quantity
0.0
0.2
0.4
0.6
0.8
1.0
1.2
a
E / V (vs. Ag/Ag+ )
a
Fig. 1. Cyclic voltammogram curve during electropolymerization of 0.01 M Py-
TEMPO in 0.1 M NaClO4-CH3CN solution.
dichloromethane (100 mL) was added slowly to the above mixture.
After addition, the mixture was warmed to room temperature
and stirred overnight. The reaction mixture was filtered and the
filtrate was concentrated under reduced pressure. The residue
was purified by column chromatography on silica gel to afford
Py-TEMPO in 86% yield.
In order to characterize the structure of Py-TEMPO by using NMR
spectroscopy, the nitroxyl radical was reduced using isoascorbic
acid according to the literature as shown in Scheme 2 [19]. 1H NMR
(500 M, MeOD) 6.68 (t, J = 1.8 Hz, 2H), 6.03 (t, J = 1.9 Hz, 2H), 5.03-
5.07 (m, 1H), 4.19 (t, J = 6.6 Hz, 2H), 2.74 (t, J = 6.6 Hz, 2H), 1.83-1.86
(m, 2H), 1.51 (t, J = 11.9 Hz, 2H), 1.18 (s, 12H). MS (ESI), m/z, 295.2
(MH+).
2.4. In situ FTIR spectroscopic study
In situ FTIR spectroscopic experiments were performed on a
Nicolet 670 FTIR spectrometer equipped with a MCT-A detector
cooled with liquid nitrogen. The disk electrode of Pt (5 mm in diam-
eter) was used as the working electrode. The resulting spectra were
defined as [20]:
ꢀR
R
R(Es) − R(ER)
R(ER)
=
(1)
In the formula, R(ES) represents single-beam spectra collected
at the sample potential (ES) and R(ER) at the reference potential
(ER). Accordingly, the negative-going bands in the resulting spectra
represented the formation of intermediates and products, while the
positive-going bands denoted the consumption of reactants. Two
hundred interferograms were collected and co-added into a single-
beam spectrum. The spectral resolution was set at 8 cm−1 and E R
was fixed at 0 mV.
2.2. Electrochemical measurement of the PPy-TEMPO electrode
CHI620B electrochemical workstation (CH Instrument Inc., USA)
was used for voltammetric study. The electrochemical polymer-
ization of the PPy-TEMPO electrode was performed on the small
Pt sheet (0.08 cm2) in 0.1 M NaClO4-CH3CN solution containing
0.01 M Py-TEMPO by cyclic voltammetry between 0 and 1.1 V at
a scan rate of 100 mV s−1. A big Pt sheet (3.0 cm2) was used as the
counter electrode and a silver/silver ion electrode (0.1 M AgNO3) as
the reference one.
3. Results and discussion
3.1. Electrochemical preparation of PPy-TEMPO
The electrocatalytic activity of the PPy-TEMPO electrode was
measured for the oxidation of benzyl alcohol in 0.1 M NaClO4-
CH3CN solution containing 10 mM benzyl alcohol and 20 mM
2,6-lutidine by cyclic voltammetry between 0 and 0.8 V at a scan
Fig. 1 shows the cyclic voltammogram for electropolymerization
of Py-TEMPO in CH3CN solution containing 0.1 M NaClO4 as the sup-
porting electrolyte. As can be seen from Fig. 1, the voltammogram
shows a pair of well-defined reversible waves at about 0.3-0.4 V
corresponding to nitroxyl radical/oxoammonium ion redox couple
(Eq.2) [21].
rate of 50 mV s−1
.
Preparative electrolysis experiments were performed on EG & G
Model 263A potentiostat/galvanostat in 0.1 M NaClO4-CH3CN solu-
tion containing 4 mmol benzyl alcohol and 20 mM 2,6-lutidine. The
anode was the PPy-TEMPO electrode with the area 3 cm2, and the
cathode was the platinum sheet electrode (3 cm2). The experiments
were carried out under a constant current 20 mA/cm2 with mod-
erate stirring. The concentrations of reactants and products were
analyzed by gas chromatograph system equipped with a capillary
column by internal standard method.
-e
+e
N
O
N
O
(2)
The characteristic irreversible oxidation peak appears at around
0.9 V attributed to the oxidation of the pyrrol moiety. Thus, it
suggests that the anodic oxidation of the pyrrole moiety in Py-
TEMPO at a Pt electrode allows the formation of the polypyrrole
film containing immobilized TEMPO on the electrode surface.
While according to the literature, it is difficult for Py-TEMPO
to be polymerized electrochemically with tetrabutylammonium
tetrafluoroborate as the supporting electrolyte due to the steric
effect from the functional groups on the pyrrole side chain [22].
The reason might be that radius of NaClO4 is less than tetrabutyl-
ammonium tetrafluoroborate.
2.3. Characterization of PPy-TEMPO electrode
Polymer films were characterized by Fourier-transform infrared
spectroscopy (FT-IR) using a Nicolet 6700 spectrometer cou-
pled with a Continu␮m microscope. The surface morphology of
PPy-TEMPO electrode was characterized by scanning electron
microscopy (SEM) using a Hitachi S-4700 scanning electron micro-
scope.

414
J.-j. Lu et al. / Electrochimica Acta 130 (2014) 412–417
OH
N
O
N
O
(1) NaOH
(2) H2SO4
DBU
N
N
O
+
CN
DCC, DMAP
N
H
CN
COOH
N
O
Py-TEMPO
DBU: 1,8-diazabicyclo [5.4.0] undec-7-ene
Scheme 1. Synthesis of Py-TEMPO.
O
O
isoascorbic acid
H
N
N
N
N
O
O
O
O
Scheme 2. Reduction of Py-TEMPO.
Fig. 2 shows the FTIR spectrum of PPy-TEMPO synthesized on
for catalytic oxidation of benzyl alcohol with the addition of 2,6-
lutidine (Fig. 4c): the anodic peak current is enhanced markedly
and the cathodic wave becomes smaller to some extent.
the Pt electrode. The bands at 2958 and 2927 cm−1 are attributed to
the methyl and methylene stretching bands, and 1724 cm−1 to C = O
stretching band of the ester groups [22]. Bands at 1446, 1411 cm−1
are associated with C = C skeleton vibration of PPy-TEMPO [23].
These bands constitute a typical FTIR spectrum of PPy-TEMPO. A
As shown in Fig. 5, benzyl alcohol and 2,6-lutidine themselves
show no voltammtric responses on the bare Pt electrode over
the potential range between 0 and 1.0 V. Therefore, the observed
behaviors suggest that the immobilized TEMPO on the PPy-TEMPO
electrode exhibits good catalytic ability for oxidation of benzyl
alcohol in the presence of 2,6-lutidine as the base. In addition,
PPy-TEMPO film offers sufficient permeability for benzyl alcohol to
enter the catalytic film and the oxidation reaction mainly occurs at
the surface of PPy-TEMPO or within the PPy-TEMPO layer, instead
of the substrate Pt.
very strong peak corresp−onding to ClO4 is found at 1087 cm−1
−
[24], suggesting that ClO4 is doped into the PPy-TEMPO film.
The micrograph of PPy-TEMPO electrode is shown in Fig. 3. As
can be seen from Fig. 3, the substrate Pt is almost fully covered with
the PPy-TEMPO film, and the surface coverage of PPy-TEMPO film
is homogeneous with the presence of some granules.
3.2. Cyclic voltammetric study of oxidation of benzyl alcohol
To further investigate the high conversion and selectivity of
PPy-TEMPO electrode for the oxidation of benzyl alcohol, the
voltammetric study for the PPy-TEMPO electrode as a function
of the concentration of benzyl alcohol from 0-100 mM is carried
out independently (Fig. 6). The oxidation peak current increases
with the concentration of benzyl alcohol increasing, and is almost
Fig. 4 shows cyclic voltammograms on the PPy-TEMPO elec-
trode in 0.1 M NaClO4-CH3CN solution in the presence of benzyl
alcohol and 2,6-lutidine. Axi-symmetric wave can be seen cen-
tered at about 0.4 V in Fig. 4(a), which might correspond to the
one-electron oxidation of nitroxyl radical to oxoammonium ion.
The reversible voltammetric wave observed on the PPy-TEMPO
electrode is little affected by the addition of benzyl alcohol, as
shown in Fig. 4b. However, the electrode shows typical behavior
100
95
172
1411
1446
2 9 5
4
90
8
85
80
1087
75
3000
2500
Wavenumbers (cm
2000
1500
-1
1000
)
Fig. 2. FTIR spectrum of PPy-TEMPO film.
Fig. 3. SEM image of PPy-TEMPO film.

J.-j. Lu et al. / Electrochimica Acta 130 (2014) 412–417
415
0.09
0.20
0.15
0.10
0.05
0.00
-0.05
-0.10
0.08 benzyl alcohol/mM
100
50
25
10
5
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00
-0.01
c
b
a
1
0
0.0
0.2
0.4
0.6
0.8
E / V ( vs. Ag/Ag+)
0.0
0.2
0.4
0.6
0.8
E / V (vs. Ag/Ag+)
Fig. 6. Cyclic voltammograms recordes for PPy-TEMPO electrode in 0.1 M NaClO4-
CH3CN solution in the presence of 2,6-lutidine (20 mM) with different concentration
of benzyl alcohol (0-100 mM).
Fig. 4. Cyclic voltammograms recorded for PPy-TEMPO electrode in 0.1 M NaClO4-
CH3CN solution. a) blank solution; b) benzyl alcohol (10 mM) in the absence of 2,6-
lutidine (20 mM); c) benzyl alcohol (10 mM) in the presence of 2,6-lutidine (20 mM).
proportional to the concentration. It suggests that the present
system may be applicable to the quasi-quantitative analysis of
benzyl alcohol.
3.3. In situ FTIR spectroscopic analysis
Fig. 7 shows in situ FTIR spectra obtained during oxidation
of benzyl alcohol on the PPy-TEMPO electrode in 0.1 M NaClO4-
CH3CN solution. The reference potential ER is set at 0 mV, then
the sample potential Es is varied stepwise from 0 to 800 mV and
the sample spectra are collected. The polarization time at each
potential is about 90 s. When the potentials are more positive
than 200 mV, the corresponding infrared spectra signals of positive-
going (1366 cm−1) and negative-going bands(1700, 1646, 1627,
1590, 1311, 1280, 1203, 1172 and 1114 cm−1) can be obviously
observed.
Table 1 summarizes the assignments of the peak frequen-
cies observed for all the positive-going and negative-going bands.
At approximately 300 mV, the spectra are dominated by three
Fig. 7. In situ FTIR spectra collected during catalytic oxidation of benzyl alcohol
on the PPy-TEMPO electrode in the presence of 2,6-lutidine as the base in 0.1 M
NaClO4-CH3CN solution.
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
-0.1
c
Table 1
Assignments of FTIR bands.
Band
Frequency/cm−1
Assignments
b
positive-going
negative-going
1366
1700
N-O· stretching vibration of TEMPO
C = O stretching vibration of
benzaldehyde
a
1646, 1627, 1590
1623
ring stretching vibration of
2,6-lutidinium cation
N+ = O stretching vibration of
oxoammonium ion
1311
1280
CHO in-plane bending of benzaldehyde
the ring stretching modes of
2,6-lutidinium cation
0.0
0.5
1.0
1203
1172
1114
C-O stretching vibration of
benzaldehyde
E / V(vs. Ag/Ag )
+
C-H in-plane bending of 2,6-lutidinium
cation
Fig. 5. Cyclic voltammograms recorded for the bare Pt electrode in 0.1 M NaClO4-
CH3CN solution. a) blank solution; b) benzyl alcohol (10 mM) in the absence of 2,6-
lutidine (20 mM); c) benzyl alcohol (10 mM) in the presence of 2,6-lutidine (20 mM).
-
ClO4

416
J.-j. Lu et al. / Electrochimica Acta 130 (2014) 412–417
characteristic negative-going bands at 1700, 1311 and 1203 cm−1
,
which are attributed respectively to C = O stretching vibration, CHO
in-plane bending and C-O stretching vibration of benzaldehyde
[25–27]. In addition, another important positive-going band at
1366 cm−1 is related to N-O· stretching vibration of TEMPO, show-
ing the consumption of nitroxyl radical and the occurrence of the
one electron oxidation of TEMPO [28]. Therefore, benzyl alcohol is
oxidized to benzaldehyde under the effect of oxoammonium ion
of PPy-TEMPO with the applied potentials. With the interference
from the bands nearby, the band related to N+ = O stretching vibra-
tion of oxoammonium ion at about 1623 cm−1 is not quite clear in
Fig. 7.
Meanwhile, five negative-going bands located at 1646, 1627,
1590, 1280, 1172 cm−1 are also observed clearly in Fig. 7. Three
of them, at 1646, 1627 and 1590 cm−1, can be ascribed to ring
stretching vibration of 2,6-lutidinium cation [29–31]. The other
two peaks at 1280 and 1172 cm−1 are assigned to the ring
stretching modes and C-H in-plane bending of 2,6-lutidinium
cation [32,33]. It suggests that 2,6-lutidine has received a hydro-
gen proton to generate 2,6-lutidinium cation, and this process
is essential during the oxidation reaction of benzyl alcohol to
benzaldehyde [21]. The above results could lead to the conclu-
sion that electrogenerated oxoammonium ions serve as selective
oxidizing agents for benzyl alcohol to form benzaldehyde in
the presence of 2,6-lutidine as the base. Most of the peak
intensities increase with the potential shifting to more positive
values, and oxidation of benzyl alcohol is getting more and more
fiercely.
Fig. 8. In situ FTIR spectra collected during oxidation of benzyl alcohol on the PPy-
TEMPO electrode in the presence of NaHCO3 as the base in 0.1 M NaClO4-CH3CN
solution.
Another experiment has been carried out to confirm the final
product in the oxidation of benzyl alcohol on the PPy-TEMPO elec-
trode is benzaldehyde instead of benzoic acid. Additional Na2CO3
is added to the same solution as Fig. 7, and then the FTIR spec-
tra are collected during the oxidation of benzyl alcohol on the
bare Pt electrode and PPy-TEMPO electrode respectively (Fig. 9).
As shown in Fig. 9a, the negative-going bands at 1700, 1311 and
1203 cm−1 which are related to benzaldehyde almost disappear,
while a negative-going band at about 1608 cm−1 associated with
ꢁas(COO−) of sodium benzoate emerges [34]. The significant differ-
ences between Fig. 7 and Fig. 9a indicate that the main product for
the electrooxidation of benzyl alcohol on the bare Pt electrode is
benzoic acid, and then sodium benzoate forms with the reaction
of benzoic acid and Na2CO3. However, the characteristic negative-
going bands at 1700, 1311 and 1203 cm−1 are still present during
the oxidation of benzyl alcohol on the PPy-TEMPO electrode under
In order to observe the peak of N+ = O at 1623 cm−1 clearly,
NaHCO3 is added as the base instead of 2,6-lutidine and in situ
FTIR spectra are collected in the same solution. As shown in Fig. 8,
the oxidation reaction in NaHCO3 as the base is slower than in
2,6-lutidine. Weak as they are, the characteristic bands associated
with consumption of nitroxyl radical at 1366 cm−1 and formation of
oxoammonium ion 1623 cm−1 are still present in the FTIR spectra.
It means that nitroxyl radical of TEMPO is oxidized to oxoammo-
nium ion by electrochemical oxidation. Benzyl alcohol is oxidized
to benzaldehyde under the effect of NaHCO3 and the correspond-
ing negative bands at 1700, 1311, 1203 and 1114 cm−1 are also
observed in Fig. 8.
Fig. 9. In situ FTIR spectra collected during oxidation of benzyl alcohol in 0.1 M NaClO4-CH3CN solution with benzyl alcohol, 2,6-lutidine and Na2CO3 on (a) Pt and (b)
PPy-TEMPO electrodes.

J.-j. Lu et al. / Electrochimica Acta 130 (2014) 412–417
417
the same conditions, as shown in Fig. 9b. The band at 1608 cm−1
,
References
which is related to sodium benzoate, is not observed, suggesting
high selective activity of PPy-TEMPO can prevent the overoxida-
tion of benzyl alcohol to benzoic acid. Thus, to further demonstrate
this, preparative electrolysis experiments of benzyl alcohol are per-
formed with PPy-TEMPO electrode as the anode and platinum sheet
as the cathode. The conversion of benzyl alcohol to benzaldehyde
is more than 96%.
[1] B.Z. Zhan, A. Thompson, Tetrahedron 60 (2004) 2917.
[2] R.A. Sheldon, I.W.C.E. Arends, G.J. Brink, A. Dijksman, Acc. Chem. Res. 35 (2002)
774.
[3] S.L. Regen, C. Koteel, J. Am. Chem. Soc. 99 (1977) 3837.
[4] P.L. Anelli, C. Biffi, F. Montanari, S.J. Quici, Org. Chem. 52 (1987) 2559.
[5] W. Adam, C.R. Saha-Möller, P.A. Ganeshpure, Chem. Rev. 101 (2001) 3499.
[6] T. Vogler, A. Studer, Synthesis 13 (2008) 1979.
[7] Y. Hahn, S.K. Song, Anal. Sci. 13 (1997) 329.
[8] T. Ono, M. Tsunoda, S. Takahashi, T. Obata, T. Sone, Y. Kashiwagi, Heterocycles
81 (2010) 2771.
[9] T. Osa, Y. Kashiwagi, K. Mukai, A. Ohsawa, J.M. Bobbitt, Chem. Lett. 19 (1990)
75.
4. Conclusions
[10] G. Palmisano, R. Ciriminna, M. Pagliaro, Adv. Synth. Catal. 348 (2006) 2033.
[11] S. Kishio, S. Ohki, T. Ohsaka, K. Tokuda, J. Electroanal. Chem. 452 (1998) 179.
[12] Y. Yamauchi, H. Maeda, H. Ohmori, Chem. Pharm. Bull. 45 (1997) 2024.
[13] W. Shi, H.H. Cao, C.F. Song, H.R. Jiang, J. Wang, S.H. Jiang, J. Tu, D.T. Ge, J. Membr.
Sci. 353 (2010) 151.
[14] M.C. Li, W.Y. Wang, C.A. Ma, W.X. Zhu, J. Electroanal. Chem. 661 (2011) 317.
[15] D.S. Corrigan, L.W.H. Leung, M.J. Weaver, Anal. Chem. 59 (1987) 2252.
[16] R.R. Adzˇic´, J.X. Wang, O.M. Magnussen, B.M. Ocko, Langmuir 12 (1996) 513.
[17] F. Montilla, F. Huerta, e. Morallon, J.L. Vazquez, Electrochim. Acta 45 (2000)
4271.
PPy-TEMPO is prepared and its electrochemical activity is inves-
tigated by cyclic voltammetry and in situ FTIR technique. High
electrocatalytic activity for oxidation of benzyl alcohol in NaClO4-
CH3CN with in the presence of 2,6-lutidine as the base is measured.
Based on serial experiments of in situ FTIR experiments, the mech-
anism of benzyl alcohol oxidation on the PPy-TEMPO electrode has
been proposed. Oxoammonium ion of PPy-TEMPO is generated by
one-electron oxidation, and benzyl alcohol is oxidized to benzalde-
hyde instead of benzoic acid with the high selective activity of
PPy-TEMPO. In addition, 2,6-lutidine receives a hydrogen proton
to generate 2,6-lutidinium cation, and this process is essential dur-
ing the oxidation reaction of benzyl alcohol to benzaldehyde. The
oxidation reaction of benzyl alcohol mainly occurs at the surface
of PPy-TEMPO film or within the PPy-TEMPO layer, instead of the
substrate Pt.
[18] J.E. Murtagh, S.H. McCooey, S.J. Connon, Chem, Commun. 227 (2005).
[19] Y. Ba, E. V. Mathias, US20080318907.
[20] J.T. Li, S.R. Chen, X.Y. Fan, L. Huang, S.G. Sun, Langmuir 23 (2007) 13174.
[21] M.F. Semmelhack, D.A. Cortes, C.S. Chou, J. Am. Chem. Soc. 105 (1983) 4492.
[22] T. Siu, S. Yekta, A.K. Yudin, J. Am. Chem. Soc. 122 (2000) 11787.
[23] M.C. Li, D.D. Bao, C.A. Ma, Electrochim. Acta 56 (2011) 4100.
[24] A. Benyoucef, F., Huerta, J.L. Vázquez, E., Morallon, Eur. Polym. J. 41 (2005) 843.
[25] D.M. Meier, A. Urakawa, A. Baiker, J. Phys. Chem. C 113 (2009) 21849.
[26] U. Olgun, M. Gülfen, Dyes Pigments 99 (2013) 1004.
[27] C. Keresszegi, D. Ferri, T. Mallat, A. Baiker, J. Phys. Chem. B 109 (2005) 958.
[28] T. Kurosaki, K.W. Lee, M. Okawara, J. Polym. Sci, Part A: Pol. Chem. 10 (1972)
3295.
Acknowledgements
[29] I.S. Pieta, M. Ishaq, R.P.K. Wells, J.A. Anderson, Appl. Catal. A: Gen. 390 (2010)
127.
[30] S.N. Timmiati, A.A. Jalil, S. Triwahyono, H.D. Setiabudi, N.H.R. Annuar, Appl.
Catal. A: Gen. 459 (2013) 8.
[31] E.F. Sousa-Aguiar, V.L.D. Camorim, F.M.Z. Zotin, R.L.C. Santos, Micropor. Meso-
por. Mat. 25 (1998) 25.
[32] S. Cinta, C. Morari, E. Vogel, D. Maniu, M. Aluas, T. Iliescu, O. Cozar, W. Kiefer,
Vib. Spectrosc. 19 (1999) 329.
[33] C. Matthäus, R.A. Wheeler, Spectrochim. Acta, Part A 57 (2001) 521.
[34] X.H. Guan, G.H. Chen, C. Shang, J. Environ. Sci. 19 (2007) 438.
This work is supported by the National Natural Science Foun-
dations of China (21206147, 21376224), Open Research Fund of
Top Key Discipline of Chemistry in Zhejiang Provincial Colleges and
Key Laboratory of the Ministry of Education for Advanced Catalysis
Materials (Zhejiang Normal University, ZJHX201304). The financial
supports are gratefully acknowledged.