Three-dimensional conductive porous organic polymers based on tetrahedral polythiophene for high-performance supercapacitors

Article abstract of DOI:10.1039/c8nj00667a

Porous organic polymers have become promising electrode materials, but their low surface area and poor electrical conductivity limit their application in high-performance supercapacitors. This study reports the facile synthesis of two porous organic polymers (POP-1 and POP-2) via the condensation of tetra(4-aminophenyl)methane and 2-thenaldehyde or 2,2-bithiophene-5-carboxyaldehyde and their subsequent polymerization. The resulting porous organic polymer materials were characterized using FT-IR, ¹³C-NMR, X-ray single crystal diffraction, SEM, TEM and N₂ adsorption-desorption measurements. This study shows that POP-2 has a diamond topological structure with a regular morphology and a wealth of pores, and a higher BET surface area (342 m² g^-1) when compared with POP-1 (260 m² g^-1). POP-2, when used as an electrode material for supercapacitors, also exhibits a much better electrochemical performance, including higher specific capacitance (332 F g^-1) and better cycle stability (capacity retention rate of more than 94% after 10000 successive cycles). These results verify that the structure and electrochemical properties of porous organic polymer materials can be effectively improved by altering the monomers. This study also provides an approach for building various porous organic polymer materials for use in high-performance supercapacitors.

Full text of DOI:10.1039/c8nj00667a

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ISSN 1144-0546
PAPER
Jason B. Benedict et al.
The role of atropisomers on the photo-reactivity and fatigue of
diarylethene-based metal–organic frameworks
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Three-dimensional conductive porous organic polymers based on
tetrahedral polythiophene for high-performance supercapacitors
Tao Li,a Wei Zhu,a Rui Shen,a Hui-Ying Wang,a Wei Chen,a Si-Jia Hao,a Yunxing Li,a Zhi-Guo Gu,a,b*
Zaijun Lia*
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
Porous organic polymer become a promising electrode material, but low surface area and poor electric conductivity limit
its application in high-performance supercapacitors. The study reports a facile synthesis of two porous organic polymers
(POP-1 and POP-2) via the condensation of tetra(4-aminophenyl)methane and 2-thenaldehyde or 2,2-bithiophene-5-
carboxaldehyde and its subsequent polymerization. The resulting porous organic polymers materials were characterized
by FT-IR, 13C-NMR, X-ray single crystal diffractometer, SEM, TEM and N2 adsorption-desorption measurements. The study
shows that the POP-2 offers a diamond topological structure with regular morphology and the rich of pores, and a higher
BET surface area (342 m2 g-1) compared with the POP-1 (260 m2 g-1). The POP-2 as an electrode material for
supercapacitors also exhibits a much better electrochemical performance, including higher specific capacitance (332 F g-1)
and better cycle stability (capacity retention rate of more than 94% after 10000 successive cycles). The results verify that
the structure and electrochemical properties of porous organic polymers materials can be effectively improved by altering
monomers. The study also provides an approach for builiding various porous organic polymers materials for high-
performance supercapacitors.
www.rsc.org/
restacking and aggregation structures, which would obviously
limit the diffusion of ions, and then led to poor cycle life and
low rate of charge-discharge.29-31 It is necessary to design new
Introduction
Supercapacitors have attracted a great deal of attention in
academia and industry during the last few decades because of
their merit of high power density, rapid charge-discharge rate,
long cycle life, low weight, and high flexibility.1-6 Therefore,
various materials have been explored to fabricate electrodes,
including carbon-based materials,7-12 metal oxides,13-15
conductive polymers,16-18 and the composites of these
materials.19-22 In particular, conductive polymers have received
increasing attention owing to their unique conjugated
structures, excellent electric conductivity and mechanical
flexibility, and controllable physical properties.23-26 Some
conductive polymers exhibit high specific capacitance due to
good electric conductivity, e.g., 950 F g-1 for polyaniline
nanowires arrays,27 and 380 F g-1 for polypyrrole hydrogels.28
However, the most of conductive polymers generally show low
specific surface area and wide pore distribution owing to their
1 D structures. Even 2D conductive polymers with conjugated
backbones still exhibit disappointed results due to the strong
porous conductive polymers for improving the capacitance
performance.
Porous organic polymers are a unique class of porous
polymers which have emerged as promising energy storage
because of their high specific surface area and controllable
pore structures, rapid ion diffusion properties, and variable
chemical functionality.32-34 Unfortunately, a key weakness of
porous organic polymers is poor electric conductivity, which
hindered their practical application in supercapacitors. To
effectively utilize porous organic polymer electrode materials,
either composites35 or carbonization36-39 of porous organic
polymers was developed to improve their specific capacitance.
However, those methods led to a significant degradation from
the theoretical advantages of porous organic polymers, which
have largely limited their potential applications. Therefore, the
design and synthesis of conductive porous organic polymers in
supercapacitors applications is highly desirable. 3D conductive
porous network can provide much more open channels to
allow efficient ionic transport and circumvent the severe
drawback of low dimensional conductive polymer materials.
However, the preparation of 3D porous organic polymers with
good electric conductivity and proper pore structure is still a
major challenge.
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To develop 3D conductive porous organic polymers as
Journal Name
electrode materials in supercapacitors, smartly choosing
building blocks with targeted 3D framework is very necessary.
The tetrahedral building blocks with sp3 hybridized carbon
atoms enable the formation of 3D diamond structure.40 We
propose to design tetrahedral building blocks by introducing
conductive units of thiophene, and then construct 3D porous
organic polymers by polymerization. In this paper, tetrahedral
building blocks were firstly synthesized via Schiff-base reaction
of tetra(4-aminophenyl)methane (TAPM) and linear 2-
thenaldehyde (THE) or 2,2-bithiophene-5-carboxaldehyde
(THC), and then two 3D conductive porous organic polymers
POP-1 and POP-2 with diamond topological structures were
formed by oxidative polymerization of tetrahedral building
blocks (Fig. 1). Herein, the syntheses and characterizations of
these polymers, and their applications as electrode materials
for supercapacitors with remarkable electrochemical
performance and excellent cycle stability were present.
Experimental section
Preparation of tetra (4-aminophenyl) methane (TAPM)
TAPM was prepared according to the reported method with
slight modifications as follows.41,42 Tetraphenylmethane (16 g,
50 mmol) was added into nitric acid (60 mL) at -40 °C by
vigorous stirring. Then acetic anhydride (25 mL) and acetic acid
(45 mL) were slowly added, respectively, and stirred for 8 h.
After filtration, the resultant precipitate was washed with
water (3
× 50 mL) and ethanol (1 × 50 mL), the residue was
collected and dried at 60 °C under vacuum to get tetrakis(4-
nitrophenyl)methane as yellow crystalline solid, yield 74%.
Tetrakis(4-nitrophenyl)methane (5 g, 10 mmol), hydrazine
monohydrate (20 mL) and Raney Ni (1.5 g) were added to THF
(80 mL). The reaction mixture was heated at 60 °C for 24 h.
After removal of the insoluble solid by filtration, the resultant
filtrate was evaporated under reduced pressure to obtain
white solid. The raw product was purified by flash column
Fig.1 The structure of 3D porous organic polymers, (a) POP-1 and (b) POP-2.
71.40, N 7.40, H 4.26, S 16.94; found C 71.23, N 7.26, H 4.70, S
16.81; FT-IR (KBr, cm-1): 1650, 1620, 1499, 1426, 1180, 1043,
1007, 961, 843, 706; 1H NMR (DMSO-d6, 400 MHz, δ ppm):
chromatography
(petroleum
ether/ethyl
acetate/dichloromethane (6:1:0.9); silica gel, 200-300 mesh) to
gain crystalline TAPM with 86% yield. Elemental analysis
calculated (%): C 78.91, N 14.73, H 6.36; found: C 78.75, N
14.58, H 6.67; FT-IR (KBr, cm-1): 3394, 3150, 3022, 1698, 1268,
1610, 1179, 859, 815, 711; 1H NMR (DMSO-d6, 400 MHz, δ
7.21 (m, 20H), 7.66 (m, 4H), 7.82 (m, 4H), 8.83 (s, 4H) (Fig. S2)
.
MTH-1 (0.76 g, 1 mmol) was dissolved in 40 mL of CHCl3.
Anhydrous FeCl3 (2.27 g, 14 mmol) was previously dissolved in
CH3NO2 (20 mL) and then slowly added into the monomer solution
at 0 °C, the precipitation was immediately obtained, the solution
was kept vigorously stirring for 24 h. The resultant precipitate
was isolated by filtered, and washed with 1 M HCl (5 × 20 mL)
and CH3OH (3 × 20 mL), Soxhlet extracted by methanol 24 h,
and then the precipitate was dried at 80 °C under vacuum for
12 h to afford bright brown powder corresponding POP-1 with
85% yield. Elemental analysis for the calculated (%): C 72.08, N
7.18, H 4.29, S 16.45 and found C 71.89, N 7.11, H 4.67, S 16.33;
FT-IR (KBr, cm-1): 1650, 1620, 1498, 1424, 1194, 1045, 822, 733,
658, 584.
ppm): 4.92 (s, 8H), 6.39 (d, 8H), 6.68 (d, 8H) (Fig. S1)
.
Preparation of POP-1
TAPM (100 mg, 0.26 mmol) and 2-thenaldehyde (THE) (0.14
mL, 1.4 mmol) were added to methanol (30 mL), the mixture
was refluxed under N2 for 24 h. The resultant yellow
precipitate was collected by filtration and washed with
methanol (5
× 20 mL), and then dried at 60 °C under vacuum
for 12 h to obtain a yellow powder. The resultant crude
product was recrystallized with CHCl3 gave yellow crystals with
91% yield, namely MTH-1. Elemental analysis calculated (%): C
Preparation of POP-2
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Fig. 2 Schematic illustration of the constructed strategy in 3D porous organic polymers synthesis. (a) POP-1. (b) POP-2.
POP-2 was prepared by a similar procedure to that described data sets were reduced using SAINT44 and corrected for
for POP-1 except that 2,2-bithiophene-5-carboxaldehyde (THC) Lorentz and polarization effects. Absorption corrections were
instead of the THE was used, yield the corresponding applied using SADABS44 supplied by Bruker. Structures were
tetrahedral building block MTH-2 as yellow crystals with 93% solved by direct methods using the program SHELXL-97.45 All of
yield. Elemental analysis calculated (%): C 67.49, N 5.16, H 3.72, the non-hydrogen atoms except the anions were refined with
S 23.63 and observed C 67.31, N 5.08, H 4.10, S 23.51; FT-IR anisotropic thermal displacement coefficients.
(KBr, cm-1): 1647, 1602, 1580, 1505, 1439, 1231, 1053, 792,
Electrochemical measurements
696, 584; 1H NMR (DMSO-d6, 400 MHz, δ ppm): 7.25 (m, 12H),
Cycle voltammetry (CV), galvanostatic charge-discharge (GCD)
7.60 (m, 12H), 8.01 (m, 4H), 8.81 (m, 8H), 9.89 (s, 4H) (Fig. S3).
and
electrochemical
impedance
spectroscopy
(EIS)
The organic polymer POP-2 was obtained as brown powder by
oxidative polymerization of tetrahedral building block MTH-2,
yield 86%. Elemental analysis calculated (%): C 68.01, N 5.07, H
3.72, S 23.20 and found C 67.82, N 5.02, H 4.18, S 22.98; FT-IR
(KBr, cm-1):1632, 1580, 1491, 1439, 1342, 1231, 1157, 1045.
measurements were performed by an electrochemical
workstation (CHI 660E). For the three-electrode systems,
Hg/HgO electrode served as the reference electrode, platinum
foil (1 cm2) acted as the counter electrode, and the prepared
electrode (1 cm2) was used as working electrode. The working
electrode was fabricated by mixing active material, acetylene
Material characterization
The FT-IR spectra of samples were characterized using a black and poly(tetrafluoroethylene) in a mass ratio of 8:1:1,
NicoletiS10 instrument in the range 4000-500 cm-1. X-ray and then dispersed in ethanol under ultrasonication to obtain
diffraction (XRD) patterns were obtained on a Bruker D8 X-ray a homogeneous slurry. The slurry was coated on the Ni foam
diffractometer. Scanning electron microscopy (SEM) images substrate (1 cm2). Similarly, in the two-electrode system, an
were collected using a Hitachi S-4800 field-emission SEM asymmetric supercapacitor was assembled to test the device
microscopy. Transmission electron microscopy (TEM) images performance, with POP-2 acting as the positive electrode,
were observed by JEOL Jem-2100 plus field-emission TEM activated carbon (AC) as the negative electrode. All the
microscopy. Thermogravimetric analysis (TGA) was carried out electrochemical tests were taken on using 3 M KOH aqueous
via Mettler Toledo TGA/DSC1/1100SF analyser. The surface electrolyte.
area and pore size distribution measurements were conducted
on
The specific capacitance of electrodes was calculated by
a
Micromeritics ASAP2020MP procedure. Solid-state the following equation (1) and equation (2):46
nuclear magnetic resonance (13C-NMR) spectra were carried
out on a Bruker AVANCE III 400 spectrometer. The liquid 1H
NMR spectra were recorded on Bruck 400 spectrometer, with
the DMSO (2.50 ppm) as internal reference. The electric
conductivity was performed by a Four-probe Tester at room
temperature (ST2258A). The crystal structures were
determined on a Siemens (Bruker) SMART CCD diffractometer
t (Umin
)
(1)
(2)
Eint/ D = I
U (t)dt
∫
t (Umax
)
2Eint/D
Um2ax
Cint/D
=
Where Eint/D stands for the discharge energy (W s),
represents the current density (A g-1),
refers to the discharge
time (s), is the potential window (V) and Cint/D is the specific
capacitance (F g-1).
I
t
using monochromated Mo Kα radiation (λ = 0.71073 Å). Cell
parameters were retrieved using SMART software and refined
using SAINT43 on all observed reflections. The highly redundant
U
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Fig. 3 The single-crystal structure of MTH-1 (ORTEP, 30% ellipsoids. All H atoms
Fig. 5 (a) SEM images of (a) POP-1 and (b POP-2; (c) TEM images of (c) POP-1 and
(d) POP-2.
have been removed for clarity. C: grey; N: blue; S: yellow).
formed between aniline and thiophene, and four Schiff-base
arms extend along the tetrahedral direction with an average
angle of 119°. Therefore, it is easy to infer that MTH-1 can be
used as precursors to construct 3D porous organic polymers.
The formation of POP-1 and POP-2 were confirmed by FT-
IR and NMR spectroscopic methods. In the FT-IR spectra, the
absorptions at 1620 cm-1 for MTH-1 and POP-1 are assigned to
the stretching vibration of C=N (Fig. 4a).48 And the
disappearance of the N-H stretching band (3394, 3150 and
3022 cm-1 for TAPM) and C=O stretching band (1650 cm-1 for
THE) in the FT-IR spectra of POP-1, suggest a completed
conversion of starting materials during the polymerization.49,50
Results and discussion
POP-1 and POP-2 were prepared through a distinct and facile
two steps strategy (Fig. 2). Firstly, tetrahedral building blocks
MTH-1 and MTH-2 were synthesized by taking full advantage
of tetrahedral TAPM and simultaneously introduced the
conductive units of THE and THC. Secondly, the formed
tetrahedral building blocks were polymerized by a simple
oxidative polymerization approach. In this process, tetrahedral
building blocks control the growing direction of the segments
and the thiophene groups were linked to produce the
extended 3D diamond network structures POP-1 and POP-2
.
The similar analysis was performed on MTH-2 and POP-2
,
whereas peak at 1647 cm-1 for MTH-2 is attributed to the
stretching vibration of C=N, and the vibration peak of C=N shift
slightly from 1647 to 1632 cm-1 for POP-2 (Fig. 4b), confirming
the existence of imine bonds. The atomic precision
construction of POP-1 and POP-2 were further verified by the
13C-NMR spectra. The characteristic peaks from 62 to 144 ppm
in the spectra of POP-1 and POP-2 are assigned to the central
sp3 carbon and benzene groups (Fig. 4c and 4d), which are
consistent with the reported results.51 The peak at 152 ppm is
attributed to thiophene, while the peak appearing at 154 ppm
corresponds to a resonance of carbon for C=N band. These
results unambiguously indicated the formation of organic
Furthermore, the formed C=N bonds reduces the structural
defects of 3D polymers, increases structural rigidity and
further improves the stability of polymers.47
To further demonstrate the structures of POP-1 and POP-2
,
a single-crystal structure of MTH-1 was collected. As can be
seen from Fig. 3, four C=N bonds of building block were
polymers of POP-1 and POP-2
.
To characterize the morphology of POP-1 and POP-2
,
scanning electron microscopy (SEM) and transmission electron
microscopy (TEM) measurements were utilized (Fig. 5). The
SEM images of POP-1 and POP-2 show homogenous structure,
consisting of the aggregation of grains with uniform dimension
(Fig. 5a and 5b). In the TEM images, both POP-1 and POP-2
have a cross-linked network structure, which can be ascribed
to the existence of well-ordered 3D frameworks (Fig. 5c and 5d,
magnification TEM images in Fig. S4).
The permanent porous properties of POP-1 and POP-2
were investigated by N2 adsorption-desorption measurements
at 77 K. The adsorption curves of POP-1 and POP-2 exhibited
Fig. 4 Spectra of FT-IR and NMR, (a) FT-IR of MTH-1 and POP-1; (b) FT-IR of MTH-
1 and POP-2; (c) 13C NMR spectra of POP-1; (d) 13C NMR spectra of POP-2.
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Fig. 6 N2 adsorption-desorption isotherms of (a) POP-1 and (b) POP-2; Pore size
distribution profiles of (c) POP-1 and (d) POP-2.
type-I and type-IV isotherms with a sharp uptake at low
relative pressure (P/P0<0.1), which is the characteristic of
microporous nature (Fig. 6a and 6b).52 The slow increase in the
range of 0.1<P/P0<0.8, and the sharp increase at high pressure
(0.8<P/P0<1.0) indicate the existence of mesoporous in both
POP-1 and POP-2. The Brunauer-Emmett-Teller (BET) surface
areas of POP-1 and POP-2 were estimated to be 260 and 342
m2 g-1, respectively. The pore size of POP-1 and POP-2 were
widely distributed and centred around the range of
microporous and mesoporous (Fig. 6c and 6d). Compared with
Fig. 7 Electrochemical performance characteristic of POP-1 and POP-2, (a) CV
curves of POP-1 at different scan rates; (b) CV curves of POP-2 at different scan
rates; (c) GCD curves of POP-1 at different current densities; (d) GCD curves of
POP-2 at different current densities; (e) Cycle stability of POP-1 and POP-2 at a
current density of 1 A g-1, inserts show GCD curves of the first ten cycles of POP-1
and POP-2 at the current density of 1 A g-1, respectively; (f) Specific capacitance
of POP-1 and POP-2 at different current densities.
POP-1, POP-2 provided a broad skeleton and pore owing to
the introduction of longer building block.
measurements were then studied at different current density
from 1 to 5 A g-1 to investigate specific capacitance of POP-1
and POP-2. It can be seen that the GCD curves show a sharp
change near to 0.35 V, which reveals that the specific
performance is predominantly pseudocapacitive in nature, in
agreement with CV curves. The Cs values of POP-1 could be
calculated according to the formula of the specific capacitance,
the values were 214, 190, 170, 151 and 135 F g-1 in the range
from 1 to 5 A g-1, respectively (Fig. 7c). Similar capacitance
values were obtained for POP-2, the Cs values were 332, 290,
250, 218 and 200 F g-1, respectively (Fig. 7d). Obviously, POP-1
and POP-2 both showed high specific capacitance, which could
be ascribed to an improved electric conductivity by introducing
conductive polythiophene units. Moreover, the BET and
capacitance values of TAPM are nearly zero. In comparison
The thermal stability of POP-1 and POP-2 were performed
by TGA analysis under N2 atmosphere and room atmosphere
from 40 to 800 °C. POP-1 and POP-2 showed no discernible
weight loss below 200 °C, and still retained 93% of their initial
mass at 300 °C (Fig. S5). The results demonstrate that these 3D
porous organic polymers possess high thermal stability, which
may be attributed to the rigidity of skeleton and the
conjugated diamond topology.
Four-probe measurements exhibited that the electric
conductivity of POP-1 and POP-2 can reach up to 2.1 × 10-3 and
6.7 × 10-3 S cm-1, respectively. The value of POP-2 was
comparable to reported organic polymers electrodes.53-56
Conductive ploythiophene units were embedded into the
skeleton of polymers making the resulting POP-1 and POP with
high BET surface area and proper pore size distribution good
candidates for supercapacitors. CV measurements were
carried out within the potential range of 0 to 0.6 V for POP-1
(Fig. 7a). The CV curves of POP-1 presented a pair of
symmetric redox peaks with good reversibility, verifying that
the POP-1 can be reversibly oxidized and reduced in 3 M KOH
solution. It is noticeable that the peak current rapidly increases
with scan rate and can maintain the shape of CV curves,
suggesting a rapid reaction kinetics. By comparison, the CV
curves of POP-2 showed similar redox peaks but with higher
current density, demonstrating that POP-2 has a better electric
conductivity compared with POP-1 (Fig. 7b). GCD
with POP-1, POP-2 exhibited a higher specific capacitance. The
results possibly resulted from extend conductive
polythiophene unit that can endow the sufficient space for
charge transfer and the diffusion of ions.
The cycle stability of POP-1 and POP-2 was investigated by
GCD cycle tests at 1 A g-1. After 10000 cycles, POP-1
maintained a specific capacitance of 197 F g-1 with capacitance
retention of 92%, while POP-2 maintained
a specific
capacitance of 312 F g-1 with capacitance retention of 94% (Fig.
7e). The good cycle stability of POP-1 and POP-2 can be
ascribed to the rigidity of skeleton and the conjugated
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diamond topology. The 3D rigid structure of POP-1 and POP-2
can effectively alleviate the volumetric swelling and shrinkage
during for cycling, resulting in an enhanced cycle stability,
which was also verified by GCD cycles (inserts of Fig. 7e).
Furthermore, even at the current density of 5 A g-1, the
capacitance retention of POP-2 also retain 60% of the initial Cs
indicating a high-rate stability (Fig. 7f). This may be associated
with the excellent electric conductivity.
,
To further understand the electrochemical performance of
the polymers, the Nyquist plots were analysed based on the
equivalent circuit model (Fig. 8). Re represents the total
resistance including electrolyte, electrode and separator. CPE
represents pseudocapacitor. Rct represents the charge transfer
resistance and Zw is the Warburg impedance which is
attributed to the ion diffusion and electrolyte penetration.
Each EIS plot exhibits a semi-circle in the high frequency region
and a straight part in the low frequency region. The semi-
circular arc is attributed to charge transfer resistance through
the electrode-electrolyte interface, and the straight line
represents the diffusion properties of the electrolyte through
the electrode surface.57 The charge transfer resistance Rct of
POP-1 and POP-2 were evaluated to be 35 and 19 Ω,
respectively. The transfer resistance of POP-2 was comparable
to 2D COF TpPa-(OH) (37.5 Ω),58 covalent polymer TpDAB (24.8
Ω),59 and most of the reported porous organic polymers.
Compared with POP-1, POP-2 possesses a higher electric
conductivity. Moreover, POP-2 displayed a slope that is larger
than POP-1, which suggested that the ion diffusion is faster
than that of POP-1. The property of POP-2 is attributed to its
proper pore structure.60-62 The microporous offers a high
surface area, while the mesoporous is benefit for decreasing
ion transfer barrier, and can facilitate rapid ion diffusion and
electrolyte penetration in the pore channels, which might
improve the capacitance performance.
The specific capacitance of POP-1 and POP-2 electrode
materials were found to be superior to those of the reported
microporous polymers,63,64 the most of covalent organic
polymers,58,59,65-67 and the carbon materials derived from
porous organic polymers.68-71. The specific capacitance of POP-
2
is comparable to conductive polymers and composite
electrode materials.72-74 Moreover, the excellent cycle stability
was also demonstrated by capacitance retention (Table 1).
GCD curves of POP-2 at
different current densities by
a two-electrode system; (d) The specific
capacitance of POP-2 at different current densities by a two-electrode system.
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the inherently N,S-codoping in the 3D porous organic polymers
improved the wettability and electric conductivity of the
electrode materials, and enhanced the overall capacitance by
enabling extra pseudocapacitance and double layer
capacitance.
Conclusions
A new strategy to construct 3D conductive porous organic
polymers was developed. By incorporating polythiophene units
into 3D porous skeleton, POP-1 and POP-2 exhibited tunable
pore structures, large specific surface areas, and high thermal
stability. More significantly, they can be applied as promising
electrode materials with high specific capacitance and
excellent cycle stability. This work advances 3D porous organic
polymers as
a platform for electrode materials and
supercapacitors applications. Optimization the electric
conductivity and electrochemical performance studies on
other porous organic polymers are now in progress in our
laboratory.
A two-electrode was further used to confirm the feasibility
of POP-2 electrode for the practical application in
supercapacitors, an asymmetric supercapacitor device (full-cell)
was assembled in 3 M KOH aqueous electrolyte. CV tests of AC
and POP-2 were performed by a three-electrode system (Fig.
9a). The AC (-1.0-0 V) and POP-2 (0-0.6 V) offer different
potential ranges, their combination can obviously extend the
potential range, which is benefit for improving the energy
density of supercapacitors. The CV curves of the full-cell
exhibited a pair of redox peaks in the potential range of 0–1.6
V (Fig. 9b). The result demonstrated that the combination of
AC and POP-2 can extend the potential window of the
supercapacitor, which is consistent with GCD curves of POP-2
at different current densities (Fig. 9c). The specific capacitance
of the full-cell was calculated to be 107, 100, 94, 91 and 90 F g-
1 in the range from 1 to 5 A g-1, respectively (Fig. 9d).
Acknowledgements
This work was supported by the National Natural Science
Foundation of China (21771089), the Fundamental Research
Funds for the Central Universities (JUSRP51725B,
JUSRP51513), the project for Jiangsu scientific and
technological innovation team, and the MOE & SAFEA for the
111 Project (B13025).
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