Supercapacitors based on polyelectrolyte/ferrocenyl-surfactant complexes with high rate capability

Article abstract of DOI:10.1039/c6ra02162j

In this paper, a composite of the Polyelectrolyte/Ferrocenyl-Surfactant Complexes (PFSC) coated on carbon paper (CP) was applied as an electrode material for supercapacitors. The as-prepared composite possessed a specific capacitance as high as 214 F g^-1 calculated from discharge curve with a current density of 0.8 A g^-1 and this observation was deemed to be because of its ferrocenyl moieties. Furthermore, the specific capacitances calculated from cyclic voltammograms were 145 and 103 F g^-1 at the potential scan rates of 20 and 50 mV s^-1, which kept at 77.6% and 55.4% of the corresponding value at 10 mV s^-1 (187 F g^-1). This suggested that the composite possessed a good rate capability as a novel redox active electrode material for pseudo-capacitors. In short, for the first time the composite PFSC/CP was reported as a promising electrode material for efficient supercapacitors.

Full text of DOI:10.1039/c6ra02162j

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ARTICLE
Supercapacitors Based on Polyelectrolyte/Ferrocenyl-
surfactant Complexes with High Rate Capability
Cite this: DOI: 10.1039/x0xx00000x
a
Guiping Tan, Zhiyu Cheng, *a Yongfu Qiu, *a Weiqing Huang, a Hongbo Fan,a
Biye Ren,b
Received 00th xxxxx 2016,
Accepted 00th xxxxx 2016
Abstract: In this research, a composite of the Polyelectrolyte/Ferrocenylꢀsurfactant Complexes (PFSC)
coated on carbon paper (CP) was applied as electrode materials for supercapacitors. The asꢀprepared
composite possessed a specific capacitance as high as 214 F gꢀ1 calculated from discharge curve with
current density 0.8 A gꢀ1 and this observation was deemed to originate from its ferrocenyl moieties.
Furthermore, the specific capacitances calculated from cyclic voltammograms were 145 and 103 F gꢀ1 at
potential scan rate 20 and 50 mV sꢀ1, which kept 77.6 % and 55.4 % of the corresponding value at 10 mV
sꢀ1 (187 F gꢀ1). This suggested that the composite possessed good rate capability as a novel redox active
electrode material for pseudoꢀcapacitors. In a word, for the first time the composite PFSC/CP was
reported as a promising electrode material for efficient supercapacitors.
DOI: 10.1039/x0xx00000x
www.rsc.org/
Key words: Supercapacitor; Ferrocene; PolyelectrolyteꢀSurfactant Complexes
In order to enhance rate capability for pseudoꢀcapacitors, other
electrode materials with redox couple could be considered.
1. Introduction
Supercapacitors with high power and much longer shelf and
cycle life than batteries have attracted great attention over the past
few years.1ꢀ3 Generally, electrical double layer capacitors (EDLCs)
store energy in terms of electrical doubleꢀlayer. To enhance their
capacitances, a typical strategy is to utilize carbon electrodes with
large surface areas and appropriate poreꢀsize distributions. Carbon
materials including activated carbon, carbon nanotube, carbon
spheres, porous carbon and graphene are usually used as electrodes.1ꢀ
Ferrocene and its derivatives have been used as a family of
fascinating organometallic electron mediators because of their redox
properties. They usually serve as the electron transfer media between
redox matrix and electrode in electrochemical and biological
sensors.14ꢀ17
Therefore,
Polyelectrolyte/Ferrocenylꢀsurfactant
complexes (PFSC) are expected to be used as electrode materials in
pseudoꢀcapacitors, due to their excellent redox properties originating
from that the generated electrons on ferrocenyl groups will be
conducted and separated through selfꢀassembled and ꢀorganized 3D
structures.
9
In comparison with EDLCs, pseudoꢀcapacitors are described in
terms of faradic charge transfer originating by a very fast sequence
of reversible faradaic redox, electrosorption or intercalation
processes on the surface of suitable electrodes. They are more
In this research, The PFSC was used as an electrodes material
attractive due to their higher capacitance and energy density through for pseudoꢀcapacitors and the commercial carbon papers was used as
Faradic reactions. 1ꢀ3,10 Manganese dioxide (MnO2) is considered as substrates and current collectors. The PFSC were prepared via the
one of the most promising pseudoꢀcapacitive materials because of its ionic selfꢀassembly of sodium poly(styrenesulfonate) (PSS) and (11ꢀ
superior capacitance (> 1370 F/g), environment friendly and costꢀ ferrocenylundecyl)ꢀtrimethylammonium bromide (FTMA) in
effective characteristics.11 However, pseudoꢀcapacitors based on aqueous solution. PFSC film was anchored onto the carbon paper
MnO2 often provide poor rate capability due to its low electrical (CP) to form a composite PFSC/CP through a solution casting
conductivity (10ꢀ5 ꢀ 10ꢀ6 S cmꢀ1).12,13
technique. The asꢀprepared composite possesses a specific
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capacitance as high as 214 F gꢀ1 calculated from discharge curve
with current density 0.80
gꢀ1. Furthermore, the specific
O
Fe
SOCl2
(CH2)11Br
C(CH2)10Br
NaBH4/AlCl3
THF
Fe
Fe
Br(CH2)10COOH
Br(CH2)10COCl
A
CH2Cl2
CH2Cl2 / AlCl3
capacitances calculated from cyclic voltammograms are 145 and 103
F gꢀ1 at potential scan rate 20 and 50 mV sꢀ1, which retain 77.6 %
and 55.4 % of the corresponding value at 10 mV sꢀ1 (187 F gꢀ1). This
H3C
CH2
(CH)11Br
(CH2)11
N
C2H5OH
50 OC / 48 h
Br
Fe
Fe
N(CH3)3
H3C
FTMA
indicates that the PFSC/CP composite possesses good rate capability Fig. 1 Synthesis route of ferrocenyl surfactant FTMA.
as a novel redox active electrode material for pseudoꢀcapacitors.
Br
N
2. Experimental
Fe
2.1 Materials.
f
a
c
Sodium poly(styrenesulfonate) (PSS, Aldrich, MW = 70,000) was
b
used as received. 11ꢀBromoundecyl ferrocene was synthesized
e
18
d
according to our previous report. All the other chemicals were
analytical reagents and purified according to the standard
procedures. Water used in all experiments was deionized and
filtrated by a Millipore purification apparatus with resistivity more
than 18.0 Mꢁ⋅cm.
5
4
3
2
1
δ
(ppm)
Fig. 2 1H NMR spectrum of the FTMA measured in CDCl3.
2.2 Synthesis of (11-ferrocenylundecyl)trimethylammonium
bromide (FTMA).
2.3 Preparation of PFSC and its film
The ferrocenyl surfactant FTMA was synthesized according to
The PFSC was prepared according to the following procedure:
239 mg (0.5 mmol ) of FTMA was dissolved in 5 mL of water at
about 80 ˚C and slowly added dropwise into 5 mL of boiling water
containing 103 mg (0.5 mmol of repeat unit) of PSS under stirring.
The yellow precipitate was separated by filtration, washed several
times with hot water, and dried for 76 h under vacuum at 40 ˚C. The
chemical structure of PFSC and its electron transfer reaction
equation were illustrated in Fig. 3. For preparation of complex films,
the chloroform solution of the PFSC with 2×10ꢀ5 mol Lꢀ1 (counted
for the ferrocenyl surfactant, the following is the same) was coated
on a quartz glass at room temperature and dried for 48 h under
vacuum at 40 ˚C.
19
the literature procedure.
The target product FTMA was
synthesized through uncleophilic substitution reaction between 11ꢀ
bromoundecyl ferrocene and trimethylamine. The synthetic routes
1
and H NMR spectrum of the FTMA measured in CDCl3 are shown
in Fig. 1 and Fig. 2, respectively. The characterization data are listed
1
as follows, H NMR (CDCl3, TMS) δ (ppm) 4.11 (m, 9H, H(Cp)),
3.54(t, 2H, ꢀCH2ꢀNꢀ), 3.40(s, 9H, (CH3)3ꢀNꢀ), 2.23 (t, 2H, CpꢀCH2ꢀ),
1.69 (m, 2H, ꢀCH2ꢀCH2ꢀNꢀ), 1.44ꢀ1.23 (m, 16H, CpꢀCH2ꢀCH2ꢀ
(CH2)8ꢀ). FTꢀIR (KBr) v 3092, 1466, 1105, 1000, and 816 cmꢀ1
(Characteristics of ferrocene groups absorption peaks), 2923 cmꢀ1 (vas
CH2), 2852 cmꢀ1 (vs CH2), 1631 cmꢀ1 (vs =N+=).
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750 ˚C. The differential scanning calorimetry (DSC) was carried out
with 4ꢀ5 mg of sample in a 6 mm aluminum pan on a Netzsch DSC
204 under nitrogen atmosphere at heating or cooling rate of 10˚C
minꢀ1 following the temperature sequence as room temperature →
130 ˚C → ꢀ45 ˚C → 130 ˚C. Polarized optical microscope of Zeiss
Axiophot was used with a Linkam hot stage. 1H NMR spectrum was
n
n
SO3
N
SO3
N
- e
+ e
obtained in CDCl3 solution on
a Varian INOVA 500NB
spectrometer. UVꢀvisible absorbance was measured with a Hitachi
UVꢀ3010 spectrophotometer. Polarized optical microscope (POM)
of Zeiss Axiophot was used with a Linkam hot stage. The sample
was heated from room temperature to 110 °C to remove the heat
history and then cooled to room temperature and subsequently
heated to 110 °C again at the rate of 10 °C minꢀ1. The POM photos
of the PFSC were taken at 25 and 100 °C for smetic A phase and
isotropic state, respectively. Cyclic voltammetry (CV) and
galvanostatic charge/discharge measurements were performed in a
threeꢀelectrode system using a CHI 440a electrochemical work
station, with 0.1 M Na2SO4 as the electrolyte solution. The
composite PFSC/CP with a projection area of 0.2 cm2 were used as
the working electrode, Ag/AgCl (3.0 M KCl) and a Pt wire as the
reference and counter electrodes, respectively. The electrochemical
impedance spectroscopy (EIS) measurements were carried out by
using a potentiostat (EG&G, M2273), the frequency range analyzed
was 0.1 Hz to 100 Hz with AC amplitude of 10 mV.
+
Fig. 3 Chemical structure of PFSC and its electron transfer reaction.
2.4 Preparation of PFSC/CP
As a general procedure, carbon paper (CP) electrode was sonicated
in ethanol and doubly distilled water for 30 s, respectively. A freshly
cleaned CP electrode was soaked in a solution of 0.07 mol Lꢀ1 PFSC
in chloroform for 10s. A small bottle was sealed tightly covering the
electrode to serve as a closed chamber to make chloroform evaporate
slowly. The CP electrode modified with the PFSC film (denoted as
PFSC/CP) was then dried in N2 atmosphere at room temperature.
The loading mass of the PFSC for PFSC/CP electrode are 1.0 mg
cmꢀ2.
2.6 Calculation
2.5 Characterization
The specific capacitance for the electrode can be calculated as, C =
Wideꢀangle Xꢀray diffraction (WAXD) and smallꢀangle Xꢀray
scattering (SAXS) measurements of the complex film were
performed in transmission geometry with an X’pert PRO
diffractometer (40 KV and 40 mA) using Cu Kα radiation
(wavelength λ = 0.154 nm) at room temperature. The 2θ ranged from
10º to 30º for WAXD and the scattering vector s ranged from 0.1 to
1.5 nmꢀ1 for SAXS, where s = (2/λ) sin θ. The scan step was 0.01º in
2θ with counting time of 1 s/step. Thermogravimetry (TG) was
measured with a Netzsch TG 209 under nitrogen atmosphere at
heating rate of 10˚C minꢀ1 starting from room temperature up to
ꢀ
ꢇꢃ
ꢄ
ꢀ1
( )
I U dU, where C is the specific capacitance (F g ), m
ꢃꢆ
ꢁꢂ(ꢃꢄꢅꢃꢆ)
is the mass of PFSC (g), υ is the potential scan rate (V sꢀ1), Uꢈ −
Uꢉ is the sweep potential range during (U) discharging branch and
I(U) denotes the response current density (A gꢀ1). In addition,
gravimetric capacitance for a single electrode was calculated from
the discharge curve in the threeꢀelectrode cell by the equation,
ꢑ∆ꢒ
ꢊꢋꢌꢍꢎꢏꢐ
=
, where I is the constant current (A gꢀ1), ∆t is the
∆ꢓ
discharge time, ∆V is the voltage range during the discharge
process.20
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3. Results and Discussion
3.1 Structural Analysis.
WAXD and SAXS measurements were performed and shown in
Fig. 4 for PFSC film at room temperature. In the wide angle range
(Fig. 4A), only a broad peak appeared at 2θ ≈ 17.7º, corresponding
to the distance between the conformationally disordered alkyl chains.
This indicated the nonꢀcrystalline structure in the solid PFSC at
room temperature.
In the small angle range (Fig. 4B), there were two peaks at the
equidistant position in s scale as 1:2 (the scattering vectors s of 0.32
and 0.63 nm−1 correspond to the long period of d001 = 31.3 and d002
=15.8 Å, respectively.), indicating the typical lamella mesomorphous
structure for PFSC. The results were similar to that proposed by
Fig. 4 WAXD (A) and SAXS (B) patterns of the PFSC, where s =
(2/λ) sin θ; (C) Possible structure model of the PFSC.
Antonitti et al. for the complexes of PSS and different
21
alkyltrimethyammonium derivatives.
They suggested that the
lamella was composed of two layers as polyions (polyelectrolyte and
ionic head groups) and alkyl chains (tails) and the long period
depends on the length and orientation of alkyl chains of surfactant.
With the results of Antonitti et al. 21, the thickness of the alkyl tail
layer was estimated to be 17.3 Å for PFSC. The value was close to
the tail length (∼ 18.8 Å) calculated for the stretched corresponding
alkyl chains with the given carbon numbers and ferrocenyl groups (∼
5 Å), because the increment of one carbon is about 1.25 Å to the
long period for a completely stretched alkyl chain if the chain was
21
perpendicular to the lamella.
Hence, the surfactant tails were
interdigitately arranged in a monolayer in the complexes. The
Fig. 5 UVꢀvis spectra of the PFSC in chloroform solution (a) and
solid film (b). Inset is the Hꢀaggregate model for ferrocenyl moieties
in the PFSC.
possible structure of PFSC film is schematically illustrated in Fig.
4C.
The chromophores could stack in parallel and form an angle α
between the chromophore transition dipoles and the line passing
through the dipole centers. For the Hꢀaggregate α was greater than
54.7o and for the Jꢀaggregate α was less than 54.7o. 22 Fig. 5 showed
UVꢀvis spectra of the PFSC in film and in chloroform solution.
There were usually two peaks at ca. 240 and 440 nm in the UVꢀvis
spectrum for the ferrocene and its derivatives, but the latter was very
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weak. As seen from Fig. 5, the maximum absorbance of the PFSC in from 442 ˚C for the pure PSS to 460˚C for the complexes. In a word,
chloroform solution appeared at about λmax = 240 nm, resulting from according to the higher degradation temperature, the complexes
showed higher thermal stability compared with their components due
PFSC film presented λmax at about 203 nm, which blueꢀshifts about to the ionic interaction.
the πꢀπ* electron transition of ferrocenyl moieties. In contrast, the
37 nm from
λ
max = 240 nm for the PFSC in solution, suggesting the
Only a weak endothermic peak at 93.6 °C and no glass transition
during the second heating run were detected from the DSC trace
above −45 ˚C for PFSC (Fig. 6B). There was no glass transition in
Hꢀaggregate among ferrocenyl moieties causing an increase in the πꢀ
π* transfer energy of cyclopentadiene, similar to that reported by
23
Shen et al.
on the N,Nꢀdimethylferrocenyl methylhexadecylꢀ complexes due to the stiffening of the PSS chains resulting from
ammonium (Fc16) bromide containing LB film. According to arrangement of the bound FTMA. We considered that the complexes
22
excitonꢀcoupling theory developed by Kasha et al., noncovalent
were in the liquid crystal state below Ti (93.6 °C) corresponding to
dimerization of molecules within an aggregate lowers the the transition from liquid crystal to isotropic phase as further verified
degeneracy of its excited electronic state compared to the uncoupled with POM. Fig. 6C and D illustrated POM photographs of the
monomers. For Hꢀaggregates, the higher electronic state carries all
complexes taken at 25 and 100 °C, respectively. PFSC exhibited a
of the oscillating strength while transition to the lower electronic random birefringent polygonꢀlike texture below Ti (Fig. 6C). The
(exciton) state is forbidden. As the result, the absorption of the oriented texture was observed after sheared and disappeared when
aggregate is blueꢀshifted in accordance with Kasha’s rules. 24 The temperature was above Ti (Fig. 6D). Combining with the finding
present behavior suggests that the ferrocenyl moieties of the PFSC from WAXD and SAXS, PFSC was ionic thermotropic smetic A
film would form a close molecular packing as the Hꢀaggregate, i.e., phase below Ti.
the cyclopentadienyl rings of ferrocenyl moieties are parallel to each
other and tilted in the complex film organized by the ordered
packing structure of alkyl tails. The Hꢀaggregate among ferrocenyl
moieties of PFSC film is also schematically illustrated in Fig. 4C.
3.2 Thermal Properties and POM Analysis.
In order to understand the nature of PFSC, we determined the
thermal properties with TG and DSC. TG thermograms in Fig. 6A
demonstrate that there is no significant weightꢀloss up to 220 °C for
PFSC, indicating their high thermal stability. PFSC exhibited a twoꢀ
step weightꢀloss process over 220ꢀ750 ˚C. The degradation
temperature Td1 corresponding to the first maximum weightꢀloss rate
for the PFSC is 338 ˚C, while degradation temperature Td for the
surfactants FTMA is approximately 265 ˚C. This indicates that the Fig. 6 (A) TG thermogram of the PFSC; (B) DSC traces of PFSC
thermal stability of the complex is significantly enhanced when during the second heating run at the rate of 10 °C minꢀ1; Polarized
compared with the corresponding pure surfactant as the result of
optical micrographs for PFSC: (C) smetic A phase at 25 °C, (D)
isotropic phase at 100 °C.
ꢀ
strong electrostatic interaction between ꢀSO3 (from PSS) and >N+<
(from ferrocenyl surfactant). The second maximum weightꢀlost at
about 460 ˚C is attributed to the degradation of PSS polymer in the
complex. The corresponding degradation temperature Td2 increases
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3.3 Cyclic Voltammetry and Galvanostatic Charge/discharge
Measurements
This implies that the composite PFSC/CP has excellent rate
capability as an electrode material for supercapacitors.
In order to examine the electrochemical behaviors of our
samples, their cyclic voltammograms and galvanostatic
charge/discharge results are shown in Fig.7. In Fig. 7A, the CV
curve of CP with quasiꢀrectangular was observed exhibiting their
doubleꢀlayer capacitance behaviors, and a couple of redox peaks
were examined from CV curve of PFSC/CP, indicating this
composite with obviously redox behaviours of PFSC, which similar
with other ferrocenylꢀmodified materials.
0.6 A
B
60
0.3
10 mV/s
40
0.0
CP
20
-0.3
PFSC/CP
-0.6
0
-0.4 0.0
0.4
0.8
1.2
CP
PFSC/CP
Potential (Vvs.Ag/AgCl)
1.8
1.2
200
160
120
80
C
100
D
To investigate the electrochemical effect of PFSC on the
composite PFSC/CP, the areal capacitances for CP and PFSC/CP at
scan rate 10 mV sꢀ1 are calculated as 38 and 60 mF cmꢀ2 shown in
Fig. 7B. It should be noted that their areal capacitances calculated
50
20
10
0.6
0.0
mV/s
-0.6
-1.2
-1.8
40
ꢇꢃ
ꢀ
0
ꢄ
using the equation: C = ꢔꢂ(ꢃ ꢅꢃ )
I U dU ,20 where S is the plane
( )
0
20 40 60 80 100
Scan rate (mV/s)
-0.4 0.0 0.4 0.8 1.2
Potential (V vs.Ag / AgCl)
ꢃꢆ
ꢄ
ꢆ
area of sample. The calculated results suggest that PFSC anchored
onto CP has dramatically increased the areal capacitances.
The typical CV curves for PFSC/CP at different potential scan
Fig. 7 (A) Cyclic voltammograms collected at scan rate 10 mV sꢀ1
for CP and PFSC/CP; (B) Calculated areal capacitances for CP and
PFSC/CP at scan rate 10 mV sꢀ1; (C) CV collected at different scan
rates for PFSC/CP; (D) Calculated areal capacitances of the
PFSC/CP from CV as a function of scan rate. (All the data of CV
was measured with 0.1 M Na2SO4 as the electrolyte solution.)
rates are given in Fig. 7C and they all have a couple of redox peaks
at 10, 20 and 50 mV sꢀ1 potential scan rates. This indicates that the
composite PFSC/CP has redox properties and excellent rate
capabilities.1 While, the CV curves deviating from redox peaks
shape upon potential scan rates higher than 50 mV sꢀ1 imply that the
CV processes were controlled by the relatively slow diffusion of ions
in electrolyte such as Na+, SO42ꢀ, H+ and OHꢀ or by these ions
diffusion in the twoꢀstage structure of PFSC/CP, and accordingly
The PFSC/CP exhibiting the best supercapacitor performance
was confirmed by the galvanostatic charge/discharge measurements
in the threeꢀelectrode system. In Fig. 8A, the chargeꢀdischarge
curves for PFSC/CP at different current densities generally show
symmetrical and linear profiles upon current densities larger than 2.4
A gꢀ1, suggesting its excellent supercapacitive behaviors. However,
once current densities lower than 1.6 A gꢀ1, an obvious platform
some PFSC materials under the interface does not make
a
remarkable contribution for the capacitance performance of pseudoꢀ
capacitors.25,26 The specific capacitances of PFSC/CP calculated
from cyclic voltammograms are shown in Fig. 7D. The decrease of could be clearly observed in charge or discharge curve, which is due
to the reversibility reaction of oxidation/reduction for the ferrocenyl
the specific capacitances for PFSC/CP with the increasing potential
motifs in the composite PFSC.
scan rates can be observed. Their specific capacitances at scan rates
of 20 and 50 mV sꢀ1 are 145 and 103 F gꢀ1 respectively, which retain
The typically specific capacitances for a single electrode
77.6% and 55.4% of the corresponding value 187 F gꢀ1 at 10 mV sꢀ1.
calculated from the discharge branches are shown in Fig. 8B.
Discharging at varied specific current densities 0.8, 1.6, 2.4, and 3.2
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A gꢀ1, the corresponding specific capacitances are 214, 132, 62 and
31 F gꢀ1. This also implies the excellent supercapacitive behaviors of
the composite PFSC/CP in terms of superior reversible redox
reactions taking place within the sample. At a current density 0.80 A
gꢀ1, the calculated specific capacitance for PFSC/CP is 214 F gꢀ1.
27
This value is close to 250.0 F gꢀ1 for the flat MnO2 electrode. In
addition to high rate capability, the cycle life test over 2000 cycles
for PFSC/CP was performed at a current density of 3.2 A gꢀ1 and the
results in Fig. 9A showed that the capacitance decay over 2000
cycles is ~ 12%, indicating its long cycle life.
The power capability of supercapacitors is primarily dependent
on their resistance, according to the equation ꢕ = 9(1 −
ꢋꢖ
ꢗꢘ)ꢙꢛ/16ꢜꢋꢖ, where ꢙ is the rated voltage of the supercapacitor,
ꢚ
ꢚ
ꢜꢋꢖ is the resistance of the supercapacitor and EF is the efficiency of Fig. 8 (A) Chargeꢀdischarge curves at various current densities for
the supercapacitor. 28 Usually, the resistance response is measured in PFSC/CP; (B) Areal capacitance calculated based on chargeꢀ
the pulsed mode of operation for determining the peak useable discharge curves from plot (A) as a function of current density.
power capability. The Nyquistꢀtype impedance spectra in Fig. 9B
show that only upward sloping lines for CP and PFSC/CP electrodes,
which suggesting that both electrodes have low diffusion resistance
and exhibit high power capacitive performance. 29,30
To design high performance supercapacitors utilizing pseudoꢀ
capacitance, the electronic conductivity and redox property of
electrode materials are the two facts playing the key roles in
affecting the electrochemical behaviours. In our case, the carbon
paper has well hydrophobility leading to its strong interaction with
the deposited PFSC, thus with low resistance response for
electrodes. In addition, the redox properties of PFSC are
advantageous to improve the specific capacitance for the electrode.
In brief, the composite PFSC/CP was reported for the first time as a
promising electrode material for efficient supercapacitors.
Fig. 9 (A) Capacitance retention test over 2000 cycles at a current
density of 1.0 A gꢀ1 for PFSC/CP; (B) Nyquist electrochemical
impedance spectra of CP and PFSC/CP.
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4. Conclusion
In summary, before preparing the composite PFSC/CP, the redox
active polyelectrolyteꢀsurfactant complexes PFSC were prepared via
the ionic selfꢀassembly firstly. The PFSC complex exhibited an
ordered interdigitated monolayer mesomorphous structure with the
long period of d = 3.13 nm, and was in the ionic thermotropic liquid
crystal SmA state at room temperature. Interestingly, in the complex
film, the ferrocenyl moieties formed Hꢀaggregation. Furthermore,
the complexes showed higher thermal stability compared with their
components. The electrochemical behaviors of the composite
PFSC/CP were characterized by cyclic voltammograms and
galvanostatic charge/discharge. The composite PFSC/CP possessed a
specific capacitance as high as 214 F gꢀ1. Their specific capacitances
at scan rates of 20 and 50 mV sꢀ1 are 145 and 103 F gꢀ1 respectively,
which retain 77.6% and 55.4% of the corresponding value 187 F gꢀ1
at 10 mV sꢀ1. The high capacitance and high rate capability of our
supercacitors originated from the low resistance response and the
very fast reversible faradaic redox of the composite PFSC/CP. In a
word, the composite PFSC/CP is reported for the first time, and it is
Notes and references
a
College of Chemistry and Environmental Engineering, Guangdong
Engineering and Technology Research Center for Advanced Nanomaterials,
Dongguan University of Technology, Guangdong 523808, P. R. China.
b
Research Institute of Materials Science, South China University of
Technology, Guangzhou 510640, P. R. China.
* Author to whom any correspondence should be addressed. Tel/fax: +86
769
2286
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Eꢀmail address:
mszycheng@scut.edu.cn
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DOI: 10.1039/C6RA02162J
Supercapacitors Based on Polyelectrolyte/Ferrocenyl-surfactant
Complexes with High Rate Capability
Guiping Tan, a Zhiyu Cheng, *a Yongfu Qiu, *a Weiqing Huang, a Hongbo Fan,a Biye Ren,b
a College of Chemistry and Environmental Engineering, Guangdong Engineering and Technology Research
Center for Advanced Nanomaterials, Dongguan University of Technology, Guangdong 523808, P. R.
China.
b Research Institute of Materials Science, South China University of Technology, Guangzhou 510640, P.
R. China.
*Author to whom any correspondence should be addressed. Tel/fax: +86 769 2286 1232, E-mail address:
qiuyf1979@foxmail. com or mszycheng@scut.edu.cn.
Table of Content
The composite PFSC/CP was reported as a promising electrode material for efficient
supercapacitors for the first time.