Significant Effect of Pore Sizes on Energy Storage in Nanoporous Carbon Supercapacitors

Article abstract of DOI:10.1002/chem.201705465

Mesoporous carbon can be synthesized with good control of surface area, pore-size distribution, and porous architecture. Although the relationship between porosity and supercapacitor performance is well known, there are no thorough reports that compare the performance of numerous types of carbon samples side by side. In this manuscript, we describe the performance of 13 porous carbon samples in supercapacitor devices. We suggest that there is a “critical pore size” at which guest molecules can pass through the pores effectively. In this context, the specific surface area (SSA) and pore-size distribution (PSD) are used to show the point at which the pore size crosses the threshold of critical size. These measurements provide a guide for the development of new kinds of carbon materials for supercapacitor devices.

Full text of DOI:10.1002/chem.201705465

DOI: 10.1002/chem.201705465
Full Paper
&
Porous Carbons
Significant Effect of Pore Sizes on Energy Storage in Nanoporous
Carbon Supercapacitors
Christine Young,[a, b, c] Jianjian Lin,[a, b] Jie Wang,[b, d] Bing Ding,[e] Xiaogang Zhang,[e]
Saad M. Alshehri,[f] Tansir Ahamad,[f] Rahul R. Salunkhe,[b] Shahriar A. Hossain,[g]
Junayet Hossain Khan,[g] Yusuke Ide,[b] Jeonghun Kim,[h] Joel Henzie,[b] Kevin C.-W. Wu,[d]
Naoya Kobayashi,*[i] and Yusuke Yamauchi*[g, h, j]
Abstract: Mesoporous carbon can be synthesized with good
control of surface area, pore-size distribution, and porous ar-
chitecture. Although the relationship between porosity and
supercapacitor performance is well known, there are no
thorough reports that compare the performance of numer-
ous types of carbon samples side by side. In this manuscript,
we describe the performance of 13 porous carbon samples
in supercapacitor devices. We suggest that there is a “critical
pore size” at which guest molecules can pass through the
pores effectively. In this context, the specific surface area
(SSA) and pore-size distribution (PSD) are used to show the
point at which the pore size crosses the threshold of critical
size. These measurements provide a guide for the develop-
ment of new kinds of carbon materials for supercapacitor
devices.
Introduction
C is determined by the dielectric properties of the electrode
material and reflects its ability to accommodate charge and
obtain higher specific energy values. Enlarging V is also a
common strategy to improve the specific energy, typically by
using different electrolytes. The practical operating voltage of
aqueous electrolytes is approximately 1.0–1.3 V, as H2/O2 evolu-
tion reactions occur at around 1.23 V. In organic electrolyte, V
can be expanded to approximately 2.5–2.8 V depending on
the ion size of the electrolytes.[2]
Electrochemical supercapacitors are useful in many applica-
tions because they can deliver energy at higher rates than bat-
teries while maintaining their specific power. However, the rel-
atively low specific energies of supercapacitor devices remain
a challenge that must be overcome.[1] The specific energy is
given by the formula shown in Equation (1), in which E is the
specific energy, C is the specific capacitance (Fgꢀ1), and V is
the operation window (V).
The high electrical conductivity, high surface area, and low
cost of porous carbon materials make them ideal electrodes in
electrochemical supercapacitor devices. In general, porous
1
E ¼ CV2
ð1Þ
2
[a] C. Young, Dr. J. Lin
[f] S. M. Alshehri, T. Ahamad
Key Laboratory of Sensor Analysis of Tumor Marker
Ministry of Education, College of Chemistry and Molecular Engineering
Department of Chemistry, College of Science
King Saud University, Riyadh 11451 (Saudi Arabia)
Qingdao University of Science and Technology, Qingdao 266042 (P.R. China)
[g] S. A. Hossain, J. H. Khan, Prof. Y. Yamauchi
Australian Institute for Innovative Materials (AIIM)
University of Wollongong, Squires Way, North Wollongong
NSW 2500 (Australia)
[b] C. Young, Dr. J. Lin, Dr. J. Wang, Dr. R. R. Salunkhe, Dr. Y. Ide, Dr. J. Henzie
International Centre for Materials Nanoarchitectonics (MANA)
National Institute for Materials Science (NIMS)
1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)
E-mail: y.yamauchi@uq.edu.au
[c] C. Young
[h] Dr. J. Kim, Prof. Y. Yamauchi
Faculty of Science and Engineering, Waseda University
3-4-1 Okubo, Shinjuku, Tokyo 169-8555 (Japan)
School of Chemical Engineering &
Australian Institute for Bioengineering and Nanotechnology (AIBN)
The University of Queensland, Brisbane, QLD 4072 (Australia)
[d] Dr. J. Wang, Prof. K. C.-W. Wu
Department of Chemical Engineering
National Taiwan University, No. 1, Sec. 4
Roosevelt Road, Taipei 10617 (Taiwan)
[i] Dr. N. Kobayashi
TOC Capacitor, 3-20-32 Tenryucho, Okayashi Nagano 394-0035 (Japan)
E-mail: naoya.kobayashi@tocc.co.jp
[e] Dr. B. Ding, Prof. X. Zhang
[j] Prof. Y. Yamauchi
Key Laboratory of Materials and Technologies for Energy Conversion
College of Materials Science & Engineering
Nanjing University of Aeronautics and Astronautics
Nanjing 210016 (P.R. China)
Department of Plant & Environmental New Resources
Kyung Hee University, 1732 Deogyeong-daero
Giheunggu, Yongin-si, Gyeonggi-do 446-701 (South Korea)
Supporting information and the ORCID identification number(s) for the au-
thor(s) of this article can be found under:
https://doi.org/10.1002/chem.201705465.
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carbon materials are classified into three categories according
to their pore size: macroporous (>50 nm), mesoporous (2–
50 nm), and microporous (<2 nm) materials.[3] A higher porosi-
ty yields higher surface areas, providing one of the key charac-
teristics for high-performance electrochemical supercapacitors.
Therefore, it is logical to assume that porous materials with
high surface areas will yield more active sites for adsorption/
desorption reactions and ion/electron transport in electro-
chemical applications.[4,5] However, high-surface-area carbon
electrodes tend to be more complex, and other factors play a
role in determining the capacitance. For example, in some
cases, micropores cannot bear the relatively high loading of
electrolyte guest species that mesopores can accommodate.
This can lead to internal strain and degradation of energy stor-
age with repeated charge/discharge cycles.[3] As a result, meso-
porous carbon architectures are suitable candidates for explor-
ing supercapacitor performance with various kinds of electro-
lytes, and have been a fruitful area of research for decades.
Numerous methods exist for the synthesis of mesoporous
carbon architectures. Strategies include the use of soft-tem-
plate, hard-template, and template-free methods, biomass-de-
rived carbons, architectures derived from reticular chemistry,
and so on.[6,7] In the soft-templating approach, surfactant mole-
cules and polymeric sources are co-assembled into ordered
mesostructures.[8–10] Inorganic templates (e.g., silica, alumina)
are used as hard templates for the fabrication of porous car-
bons.[8–10] Metal-organic frameworks (MOFs) and covalent or-
ganic frameworks (COFs) are highly ordered materials that can
be decomposed into highly porous carbon materials.[11] Bio-
mass resources derived from the cellulose/lignin of plants and
other agricultural wastes can also be converted into activated
porous carbons that generate relatively low total impact on
the environment during their lifecycle.[12–14]
Many decades of research have been devoted to explaining
the relationship between porosity and supercapacitor per-
formance.[15–18] Although various carbon materials have been
tested, to our knowledge, there have been no systematic stud-
ies of a large number of porous carbon samples side by side.
In this manuscript, we describe the properties of 13 porous
carbon samples synthesized through various methods. We pro-
pose that there is a threshold of the pore size (so-called “criti-
cal pore size”, P) at which guest molecules can pass through
and effectively navigate the porous network. Through careful
investigation of both the specific surface area (SSA) and pore-
size distribution (PSD) of various samples, we demonstrate the
point at which the pore size crosses the threshold of critical
size. Our findings provide a simple and quick optimization
method for the fabrication and development of new carbon
materials for industrial applications.
Results and Discussion
The preparation of the various porous carbon materials prior
to characterization is described in detail in the Experimental
Section. Initially, the surface morphology of the materials was
investigated with a scanning electron microscope (SEM, Hitachi
S-4800) at an accelerating voltage of 5 kV (Figure 1). Samples
A–D were derived from biomass materials using various ap-
Figure 1. a–m) SEM images of Samples A–M, respectively.
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proaches. Sample E was synthesized by using zinc layered hy-
droxide nitrate as a layered template.[19] Sample F was pre-
pared from MXene.[20] Samples G and H were prepared from
CaCO3 precursors.[21] Samples I–M were synthesized through a
soft-templating method by which the surface areas could be
tuned according to the synthetic conditions.[22–25]
Nitrogen (N2) adsorption/desorption isotherms were collect-
ed for all materials to determine the porosity of the carbon
samples (Autosorp operated at 77 K). The SSAs and PSDs were
analyzed by density functional theory (DFT), and the details are
summarized in Table 1. The isotherms and PSDs are shown in
Figure 2. Samples A, C, and D possessed relatively high surface
areas. However, whereas Sample A had an SSA of 1921 cm2 gꢀ1,
its volume was composed of around 60.5% micropores. On
the other hand, Samples C, D, F, H, I, L, and M were composed
of <10% micropores, suggesting a high concentration of
mesopores.
Table 1. Surface areas (S), pore volumes (V), micropore volumes (Vmicro),
and percentages of micropores (Vmicro/V) for all prepared samples. S and V
were calculated by the DFT method. Vmicro was calculated by the t-plot
method. Note that micropores here are smaller than 2 nm.
Sample
S [m2 gꢀ1
]
V [cm3 gꢀ1
]
Vmicro [cm3 gꢀ1
]
Vmicro/V [%]
A
B
C
D
E
1921
463
2007
1858
328
704
685
1547
802
753
1.2286
0.2533
1.6050
1.6212
0.2445
0.6117
0.4517
1.2930
0.8453
0.4488
0.4610
0.6870
1.5924
0.7430
0.0611
0.1429
0.1216
0.0298
0.0387
0.0822
0.0931
0.0615
0.0828
0.0619
0.0092
0.0432
60.5
24.1
8.9
7.5
12.2
6.3
18.2
7.2
7.3
18.4
13.4
1.3
F
G
H
I
J
K
L
Figure 2. a) Nitrogen adsorption/desorption isotherms and b) pore-size dis-
tributions (PSDs) of all samples.
708
540
1479
the tenth cycle was used for the calculation of capacity (see
the Experimental Section).
M
2.7
All the discharge curves are linear in the whole discharge
potential window, indicating nearly perfect capacitive behavior
(Figure 3a). As shown in Figure 3, samples C, D, F, and M show
relatively high capacities (>30 mAhgꢀ1), which may be attrib-
uted to their high SSAs in addition to a high concentration of
mesopores according to the PSDs (Figure 2b). Although Sam-
ple A had a high SSA compared with other samples, the ca-
pacity was only 18.31 mAhgꢀ1, indicating that its high percent-
age of micropores negatively affects its performance. Overall,
by comparing the capacities of these various carbon materials,
we can see that the presence of mesopores is quite important.
It is reasonable to assume that pores larger than the size of
the electrolyte ion and its solvation shell area are necessary to
obtain a high capacitance. On the basis of the above results,
we propose that there is a threshold of the pore size (so-called
“critical pore size”, P) that can adequately enable the electro-
lyte ions to pass through all the pores. From the obtained N2
adsorption isotherms, the distributions of cumulative surface
area versus pore size were obtained (Figure S1, Supporting In-
formation). To find the critical pore sizes, P, we define here the
“effective-SSA” (E-SSA, i.e., the surface area contributed from
larger pores than the selected pore sizes), as explained in Fig-
In general, several factors affect the performance of superca-
pacitors, including surface area, pore size, material morpholo-
gy/shape, conductivity, surface chemistry, and the ion size of
the electrolytes.[26] In addition, carbon materials usually show
the highest capacitances at lower current densities. Porous
carbon materials can experience a decline in capacitance
owing to insufficient charging time, which limits ion penetra-
tion through the pores of bulky particles.[27,28] To limit the influ-
ence of these various factors and focus on the influence of po-
rosity, we performed our supercapacitor measurements at cur-
rent densities of 0.4 mAcmꢀ2. We used a coin-cell 2032-type
supercapacitor device with a diameter of 20 mm and thickness
of 3.2 mm. Both positive and negative electrodes were instal-
led using the same active materials. A 10 mm diameter alumi-
num plate was used as the current collector. The electrode ma-
terial consisted of 80 wt% active material, 15 wt% conductive
agent, and 5 wt% PTFE. The electrolyte used was 2m SBPBF4
SL+DMS (9:1) solution. Galvanostatic charge/discharge curves
of all carbon samples were measured. The first ten cycles were
performed at the target current density of 0.4 mAcmꢀ2, and
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Figure 4. Relationship between specific capacity and effective surface area
(E-SSA) using a) 0 nm, b) 1.5 nm, c) 3.0 nm, and d) 4.5 nm as the selected
pore sizes. R2 is the coefficient of determination derived from the slope of
the aggregate data.
capacity is 6.3345 mAhgꢀ1. Thus, it seems reasonable that less
capacity derives from pores smaller than 3 nm, although the
mesopores dominate the performance.
Figure 3. a) Galvanostatic charge/discharge curves of supercapacitors based
on all the carbon samples in SBPBF4 electrolyte, at a current density of
0.4 mAcmꢀ2. b) Specific capacities of all carbon samples at 0.4 mAcmꢀ2
c) Total SSA and E-SSA at particular pore sizes for all the carbon samples.
.
Conclusion
The performances of numerous porous carbon materials syn-
thesized through various methods were tested in a supercapa-
citor device. We have demonstrated that there is a threshold
of the pore size (critical pore size, P) that can adequately
enable the electrolyte ions to pass through all the pores. The
highest-performing materials can be targeted by optimizing
the pore sizes. This approach to the characterization of porous
carbon materials could open a new path for the design of
carbon materials for supercapacitors, as testing is a relatively
quick process.
ure S2 (Supporting Information). To find the real critical pore
size (P), we calculated the E-SSAs by changing the selected
pore sizes from 0.5 to 5 nm. It is known that the ionic radii of
SBP+ and BF4ꢀare 0.43 and 0.227 nm, respectively, so a mini-
mum P value of 0.5 nm is reasonable if taking into account
both the ion size and its solvent shell.[29,30] As an example cal-
culation of the E-SSA, Sample A has an SSA of 1921 m2 gꢀ1,
which results in E-SSA values of 1811 and 830 m2 gꢀ1 for P
values of 0.5 and 1.0 nm, respectively.
All the E-SSA values determined with different selected pore
sizes are listed in Figure 3c. Figure 4 and Figure S3 (Supporting
Information) display the relationship between the E-SSA and
the specific capacity for all carbon samples by tuning the se-
lected pore sizes. The coefficient of determination (R2) was cal-
culated from the slope of the fitting line. The R2 values are
quite low if the selected pore sizes are set to 0 nm. Higher
values result in better R2 values, gradually increasing to 0.747
at P=3.0 nm. At P>3.0 nm the R2 values begin to decrease,
probably because mesopores larger than 3 nm in diameter
Experimental Section
Materials preparation
Sample A (Coal tar-derived activated carbon): Coal tar (1 g) was
first pre-carbonized under a nitrogen atmosphere at 6008C for 2 h
to form chars. The sample was washed three times with acetone,
ethanol, and water, and then ground together with KOH pellets (at
a mass ratio of 1:1), put in a furnace under a nitrogen atmosphere,
heated to 8008C (ramp rate: 28Cminꢀ1), and held at that tempera-
ture for 2 h. The final sample was obtained by washing with HCl
and water.
ꢀ
enable SBP+ and BF4 to pass through the pores easily. Note
that the slope of the fitting line of P=3 nm (Figure 3c) can be
expressed as y=0.0996x+6.3345, in which x represents E-SSA
and y represents specific capacity. If the E-SSA (x) is zero, the
Sample B (Jute-derived carbon #1): Jute (1 g) was ground with a
mortar and pestle into tiny fibrous pieces and then washed three
separate times with acetone, ethanol, and water. The sample was
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placed in a furnace under a nitrogen atmosphere, heated to 8008C
(ramp rate: 28Cminꢀ1), and held at that temperature for 2 h.
(0.09 g) and H2O (5 g). Carbonization was completed by pyrolysis
at 9008C under vacuum. The carbon-silica composite obtained
after pyrolysis was washed with HF solution to remove the silica
template.
Sample C (Jute-derived carbon #2): Jute (1 g) was ground with a
mortar and pestle into tiny fibrous pieces and then washed three
separate times with acetone, ethanol, and water. The sample was
placed in a furnace under nitrogen, heated to 8008C (ramp rate:
28Cminꢀ1), and held at that temperature for 2 h. The sample was
activated by grinding it together with KOH (1:1 mass ratio), after
which it was heated to 7008C (ramp rate: 28Cminꢀ1) and held at
that temperature for 2 h. The final sample was washed with HCl
and water prior to use.
Sample J (Soft-templated mesoporous carbon #1): According to
a previous paper,[23] phenol (0.61 g) was melted in a flask at 40–
428C and mixed with NaOH aqueous solution (0.13 g; 20 wt%)
under stirring. After 10 min, formalin (1.05 g; 37 wt% formalde-
hyde) was added dropwise and the sample was held below 508C.
Upon further stirring for 1 h at 70–758C, the mixture was cooled to
RT and the pH was adjusted to approximately 7.0 with HCl solu-
tion. The water was removed by vacuum evaporation below 508C,
and the final product was dissolved in ethanol (20 wt% resol-etha-
nol solution). Pluronic F127 (0.5 g) was added to this resol-ethanol
solution (5.0 g; 20 wt%). After stirring at RT for 10 min, the sample
was dried under ambient conditions for 4 h; this was followed by
thermal treatment at 1208C for 24 h. The resulting samples were
obtained after pyrolysis for 3 h at 3508C (ramp rate: 18Cminꢀ1).
Mesoporous carbon was obtained after carbonization under nitro-
gen at 8008C (ramp rate: 18Cminꢀ1) and holding at that tempera-
ture for 2 h.
Sample D (Jute-derived carbon #3): Jute (1 g) was ground with a
mortar and pestle into tiny fibrous pieces and then washed three
separate times with acetone, ethanol, and water. The sample was
placed in a furnace under nitrogen, heated to 8008C (ramp rate:
28Cminꢀ1), and held at that temperature for 2 h. Finally, the ob-
tained carbon was activated by grinding it together with KOH (1:1
mass ratio) and then heating at 8008C for 2 h. The final sample
was washed with HCl and water prior to use.
Sample E (Porous carbon nanosheets): The preparation of this
sample followed an existing method.[19] Zinc nitrate hexahydrate
(11.9 g) was dissolved in distilled water (200 mL) and the pH was
changed gradually to 7.0 with 0.5m NaOH solution. The resulting
precipitate was dried overnight. The precipitate (1 g) was suspend-
ed in 0.5m gallic acid (250 mL) and then stirred vigorously for 2 h
at room temperature (RT) under nitrogen. Next, the sample was
heated (again under nitrogen) to 9508C (ramp rate: 58Cminꢀ1) and
held at that temperature for 2 h. The final sample was washed
with HCl and water prior to use.
Sample K (Soft-templated mesoporous carbon #2): According to
a previous paper,[24] the mesoporous carbon was prepared through
a simple method using atom-transfer radical polymerization. Typi-
cally, the resol precursor (2.0 g, containing 0.25 g phenol and
0.15 g formaldehyde) was added to tetrahydrofuran (THF) solution
(5.0 g, containing 0.1 g PEO125-b-PS230 copolymer) and then stirred
to form a homogeneous solution. The solution was poured into a
dish to evaporate ethanol at RT in ꢁ5–8 h, then heated in an oven
at 1008C for 24 h. The product was removed from the dish and
ground into a fine powder. The obtained sample was calcined at
8008C for 3 h under nitrogen to obtain the mesoporous carbon.
Sample F (MXene-derived carbon): According to
a previous
paper,[20] Ti3AlC2 powder (2 g) was suspended in HF solution
(25 mL; 40 wt%) at RT for 24 h. The resulting precipitate was
washed thoroughly with deionized water to form the MXene, then
dried under vacuum at RT for two days. The dried MXene was
placed into a horizontal quartz tube furnace, which was then
purged with argon and heated to 9008C. Subsequently, it was ex-
posed to dry chlorine gas for 2 h. After chlorination, the samples
were held at 6008C for 2 h under flowing ammonia gas to remove
residual chlorine and chlorides trapped in the pores.
Sample L (Ordered mesoporous carbon prepared from carbon-
silica nanocomposite #1): According to a previous paper,[25] block
copolymer F127 (1.6 g) was dissolved in ethanol (20.0 g, containing
1.0 g of 0.1m HCl solution). The sample was stirred for 1 h at 408C
to make a clear solution. Then, tetraethoxysilane (TEOS; 2.0 g) was
dissolved in this solution. Next, resol-ethanol solution (5.0 g,
20 wt%) was added to the solution, which was then stirred for 1 h
at RT. All three components of the sample were assembled during
this one-step process. The assembled mixture was transferred to a
dish and dried for 1 h at RT. After evaporation of the ethanol, ther-
mal polymerization was conducted at 1008C for 24 h in an oven.
The resulting thin film was removed from the dish, carbonized
under nitrogen at 3508C (ramp rate: 18Cminꢀ1), and held at that
temperature for 3 h, then at 8008C (ramp rate: 58Cminꢀ1), holding
at that temperature for 2 h. The resulting carbon-silica composites
were immersed in HF solution (10 wt%) for 24 h to remove the
silica, and then washed with water.
Sample G (Porous carbon prepared from CaCO3 #1): According
to a previous paper,[21] Na2CO3 solution (0.33m) and CaCl2 solution
(0.033m) were dissolved in deionized water (100 mL). Dopamine
hydrochloride was dissolved in tris(hydroxymethyl)aminomethane
solution (10 mm) and the pH was adjusted to 8.5. This solution was
stirred vigorously for 24 h. The sample was separated by centrifu-
gation, and the resulting CaCO3-polydopamine composite was
heated under nitrogen at 8008C (ramp rate: 28Cminꢀ1) and held at
that temperature for 2 h. The final sample was washed with HCl
and water prior to use.
Sample M (Ordered mesoporous carbon prepared from carbon-
silica nanocomposite #2): The synthetic approach was similar to
that for Sample L. Block copolymer F127 (1.6 g) was dissolved in
ethanol (8.0 g, containing 1.0 g of 0.2m aqueous HCl). The sample
was stirred for 1 h at 408C to make a clear solution. Next, TEOS
(2.0 g) and resol-ethanol solution (5.0 g; 20 wt%) were added se-
quentially to the solution, which was then stirred for 2 h. The mix-
ture was transferred to a dish and dried for 1 h at RT. After total
evaporation of the ethanol, thermal polymerization was conducted
at 1008C for 24 h in an oven. The resulting thin film was removed
from the dish and carbonized under nitrogen at 3508C (ramp rate:
18Cminꢀ1), holding at that temperature for 3 h, then at 9008C
(ramp rate: 58Cminꢀ1), holding at that temperature for 2 h. The re-
sulting carbon-silica nanocomposites were immersed in HF solu-
Sample H (Porous carbon prepared from CaCO3 #2): The synthe-
sis method was similar to that of Sample G except that the CaCO3-
polydopamine composite was heated under nitrogen at 8008C
(ramp rate: 58Cminꢀ1) and held at that temperature for 2 h.
Sample I (Hard-templated mesoporous carbon CMK-3): The prep-
aration of mesoporous carbon CMK-3 has been reported previous-
ly.[22] SBA-15 (1 g) was added to a mixture of sucrose (1.25 g) and
H2SO4 (0.14 g) dissolved in H2O (5 g). The mixture was placed in a
drying oven for 6 h at 1008C, and then for 6 h at 1608C. The
sample turned dark brown or black during the treatment in the
oven. The silica powders containing partially polymerized and car-
bonized sucrose were treated again at 100 and 1608C using the
same drying technique after the addition of sucrose (0.8 g), H2SO4
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Electrochemical characterization
The electrochemical measurements were performed with a 2032-
type coin-cell supercapacitor device. Both positive and negative
electrodes were installed using the same active materials. A 10 mm
diameter aluminum plate served as the current collector. The elec-
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density of 0.4 mAcmꢀ2 during the first ten cycles. The discharge
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the formula C=IꢁDt/(mꢁDV), in which
C is the capacity
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This work was partly supported by an Australian Research
Council (ARC) Future Fellow (FT150100479), JSPS KAKENHI
Grant Number 17H05393 (Coordination Asymmetry), Ministry
of Science and Technology, Taiwan (106-2811-E-002-023), the
Natural Science Foundation of the Higher Education Institu-
tions of Jiangsu Province (16KJB430015), the National Natural
Science Foundation (NNSF) of China (61604070), and the Na-
tional Natural Science Foundation of Jiangsu Province
(BK20161000). The authors extend their appreciation to the In-
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University (KSU) for funding this research work through ISPP-
0097.
Conflict of interest
The authors declare no conflict of interest.
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Keywords: carbon · electrochemistry · mesoporous materials ·
nanoporous carbon · supercapacitors
[1] L. Q. Mai, A. Minhas-Khan, X. C. Tian, K. M. Hercule, Y. L. Zhao, X. Lin, X.
Xu, Nat. Commun. 2013, 4, 2923.
Manuscript received: November 17, 2017
[2] C. Zhong, Y. D. Deng, W. B. Hu, J. L. Qiao, L. Zhang, J. J. Zhang, Chem.
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Version of record online: && &&, 0000
&
&
Chem. Eur. J. 2018, 24, 1 – 7
www.chemeurj.org
6
ꢀ 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!

Full Paper
FULL PAPER
Designing supercapacitor materials:
Several porous carbon samples were
tested in supercapacitor devices. There
is a “critical pore size” at which guest
molecules can pass through the pores
effectively. Measurements of specific
surface area (SSA) and pore-size distri-
bution (PSD) provide a guide for the de-
velopment of new kinds of carbon ma-
terials for supercapacitor devices (see
figure).
&
Porous Carbons
C. Young, J. Lin, J. Wang, B. Ding,
X. Zhang, S. M. Alshehri, T. Ahamad,
R. R. Salunkhe, S. A. Hossain, J. H. Khan,
Y. Ide, J. Kim, J. Henzie, K. C.-W. Wu,
N. Kobayashi,* Y. Yamauchi*
&& – &&
Significant Effect of Pore Sizes on
Energy Storage in Nanoporous Carbon
Supercapacitors
Chem. Eur. J. 2018, 24, 1 – 7
www.chemeurj.org
7
ꢀ 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ