Copyright WILEY-VCH Verlag GmbH & Co. KGaA, 69469 Weinheim, Germany, 2014.
Supporting Information
for Small, DOI: 10.1002/smll.201402222
One-Step Synthesis of Single-Layer MnO2 Nanosheets with
Multi-Role Sodium Dodecyl Sulfate for High-Performance
Pseudocapacitors
Zhenning Liu, Kongliang Xu, Hang Sun,* and Shengyan Yin*
Supporting Information
One-step Synthesis of Single-layer MnO2 Nanosheets with Multi-role Sodium Dodecyl
Sulfate for High-performance Pseudocapacitors
Zhenning Liu, Kongliang Xu, Hang Sun*, and Shengyan Yin*
Dr. Z. Liu, K. Xu, Dr. H. Sun
Key Laboratory of Bionic Engineering (Ministry of Education), College of Biological and
Agricultural Engineering, Jilin University, Changchun, Jilin 130022, P. R. China
E-mail: [email protected]
Dr. S. Yin
State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and
Engineering, Jilin University, Changchun, Jilin 130012, P. R. China
E-mail: [email protected]
Figure S1. Photograph of MnO2 colloidal suspension stored at 4 °C in the dark for 6 weeks.
1
Figure S2. AFM measurement of overlapping MnO2 nanosheets. Left: AFM image of
overlapping MnO2 nanosheets on a mica substrate; right: the height profile along the black
line in the left image. The height difference between two red arrows is ~0.77 nm.
Figure S3. A zoom-out AFM image of MnO2 nanosheets including the areas shown in Figure
2e and S2. The height differences between paired arrows in green, red, and black are 0.78,
0.98, and 0.97 nm, respectively.
2
Figure S4. Raman spectrum of MnO2 nanosheets.
Figure S5. UV-Vis spectra and photographs (inset) of the Reaction 2 (no SDS) in Table 1 at
0-min and 60-min respectively. Unchanged UV-Vis spectrum at 60-min indicates that there
was no MnO2 formed after heating the reaction for 60 minutes.
3
Figure S6. Control reactions with different concentrations of KMnO4 and acid. a) UV-Vis
spectra of the reactions with different concentrations of HCl: before heating (black line),
Reaction S1 (red line, 1 mM [H+]), Reaction S2 (blue line, 100 mM [H+]), Reaction S3
(purple line, 500 mM [H+]), and the photograph of Reaction S3 (inset); b) UV-Vis spectra of
the reactions with the same [H+] (500 mM) of HCl and H2SO4: before heating (black line),
Reaction S3 (purple line, HCl), and Reaction S4 (blue line, H2SO4); c) UV-Vis spectra of the
reactions with different concentrations of H2SO4: before heating (black line), Reaction S5 (red
line, 10 mM [H+]), Reaction S6 (blue line, 200 mM [H+]) and Reaction S7 (purple line, 2000
mM [H+]); d) UV-Vis spectra of the reactions with different heating time: before heating
(black line), Reaction S7 (purple line, 60 minutes), reaction S8 (blue line, 300 minutes), and
the photograph of reaction S8 (inset). Please refer to Table S2 for details of the control
reactions.
4
Figure S7. Photograph of Reaction 3 (dodecanol in place of SDS) in Table 1 at 60-minute. A
large amount of flocculent aggregate was formed and the solution turned yellow at 60-minute
and became clear eventually.
Figure S8. UV-Vis spectrum of the Reaction 4 (SDS at stoichiometric molar ratio instead of
excess amount as used in the synthesis reaction) in Table 1. The remaining absorption of
KMnO4 indicates that KMnO4 hadn’t been reduced completely.
5
Figure S9. UV-Vis spectra and photographs (inset) of the Reaction 5 (SDBS in place of SDS)
in Table 1 at 0-min and 60-min respectively. Unchanged UV-Vis spectrum at 60-min
indicates that there was no MnO2 formed after heating the reaction for 60 minutes.
Figure S10. UV-Vis spectrum of the Reaction 6 (SDSo in place of SDS) in Table 1. The
absorption at 318 nm indicates the formation of multi-layer MnO2 nanosheets.
6
Figure S11. (a) SEM image of MnO2 nanosheet powder dried from a concentrated solution
without substrate; (b) SEM image of (a) at higher magnification. MnO2 nanosheets aggregated
into thick stacked flakes when dried without substrate, much bigger and thicker than the
nanosheets dried on substrate (Figure 2c and 2d).
Figure S12. N2 adsorption isotherm of MnO2 nanosheets at a degas temperature of 300 °C.
7
Figure S13. (a) CV curve of acetylene black electrode at a scan rate of 20 mV s-1 ; (b)
galvanostatic charge/discharge curves of acetylene black electrode at 0.5 A g-1 and the
capacitance calculated is ~8 F g-1.
Figure S14. Galvanostatic charge/discharge curves of c-MnO2 at 3 A g-1 and the capacitance
calculated is ~31 F g-1 after subtracting the contribution of the acetylene black and Ni foam.
8
Figure S15. (a) CV curve of symmetric acetylene black/acetylene black pseudocapacitors at a
scan rate of 20 mV s-1 ; (b) galvanostatic charge/discharge curves of symmetric acetylene
black/acetylene black pseudocapacitors at 0.1 A g-1 and the capacitance calculated is ~2 F g-1.
Figure S16. SEM image of c-MnO2 on the electrode of Ni foam.
9
Table S1. Summary of recent reports on MnO2 nanomaterials synthesized from KMnO4 in
acidic solution.
Concentration of
Concentration
Reaction
Reaction
temperature (°C)
time (h)
Acid
Morphology
Reference
12
Urchin-like
[1]
20, 60, 100
10
Layered
[2]
HCl
140
1
nanosheets
[3]
350
HCl
60
0.5
nanoflakes
[4]
1
H2SO4
95
1
no reaction
Our work
KMnO4 (mM)
of H+ (mM)
1240
1780
HNO3
120
750
500
HCl
55
387
19.4
0.5
Table S2. Control reactions with different concentrations of KMnO4 and acid.
Reaction*
Concentration of
KMnO4 (mM)
Concentration of
H+ (mM)
Acid
Reaction
time (min)
Color before
reaction
Color after
reaction
2 in Table 1
0.5
1
H2SO4
60
Purplish red
Unchanged
S1
0.5
1
HCl
60
Purplish red
Slightly changed
S2
0.5
100
HCl
60
Purplish red
S3
0.5
500
HCl
60
Purplish red
Wine red
Brown
precipitates
S4
0.5
500
H2SO4
60
Purplish red
Unchanged
S5
5
10
H2SO4
60
Purplish red
Unchanged
S6
5
200
H2SO4
60
Purplish red
Unchanged
S7
5
2000
H2SO4
60
Purplish red
Slightly changed
S8
5
2000
H2SO4
300
Purplish red
Brown
precipitates
*: All reactions were carried out at 95 °C.
Table S3. Summary of recent reports on surfactant-assisted synthesis of MnO2 nanomaterials
from KMnO4.
Concentration
of KMnO4
(mM)
33.3
5
10
0.5
Surfactant
Sodium bis(2ethylhexyl)
sulfosuccinate (AOT)
2-(N-morpholino)
ethanesulfonic acid
(MES)
Hexadecyltrimethylam
monium bromide
(CTAB)
Sodium dodecyl sulfate
(SDS)
Concentration
of surfactant
(mM)
Reaction
temperature
(℃)
Reaction
time (h)
Proposed
mechanism
66.6
RT
5
Redox
[5]
50
Sonicated
0.5
Redox
[6]
50
140 (hot
injection)
Unmenti
oned
Redox
[7]
10
95
1
Redox
Our work
10
Reference
Table S4. Summary of pseudocapacitive properties of MnO2 nanosheets reported in recent
literature.
Thickness
SC
Scan rate or
(nm)
(F g-1)
current density
nanosheets
unmentioned
103.5
nanolamellas
unmentioned
nanosheets
Morphology
MnO2: C: Binder
Electrolyte
Reference
0.5 A g-1
8:1:1
1 M Na2SO4
[3]
149.7
2 A g-1
8:1.5:0.5
1 M Na2SO4
[8]
~2 nm
182
0.1 A g-1
4.5:4.5:1
0.1 M Na2SO4
[9]
nanoflakes
3~5 nm
328
5 mv s-1
MnO2 on the stainless
steel substrate
1 M Na2SO4
[4]
nanosheets
~2 nm
~500
1 A g-1
7:2:1
2 M Ca(NO3)2
[5]
nanosheets
~2 nm
532.5
2 mv s-1
MnO2 powder coated on
titanium substrate
1M Na2SO4
[10]
nanosheets
~14.3 nm
1183
5 A g-1
8.5:1:0.5
Saturated K2SO4
[11]
nanosheets
single-layer
868
3 A g-1
7:2:1
1 M Na2SO4
Our work
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