Electronic Supplementary Material (ESI) for Journal of Materials Chemistry A.
This journal is © The Royal Society of Chemistry 2017
Electronic Supplementary Material (ESI) for Journal of Materials Chemistry A
High area-specific capacitance of Co(OH)2/hierarchical nickel/nickel
foam supercapacitor and increase with cycling
Zheyin Yu,[a] Zhenxiang Cheng*,[a] Xiaolin Wang,[a] Shi Xue Dou,[a] and Xiangyang Kong[b]
a
Institute for Superconducting and Electronic Materials, University of Wollongong, North Wollongong, NSW
2500, Australia. E-mail: [email protected]; Fax: +61-2-42215731; Tel: +61-2-42981406
b
School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, PR China
Experimental Section
All chemicals were of reagent quality and used without further purification. The nickel
chloride, annonium chloride, ethylenediamine hydrochloride, sodium nitrate, cobalt nitrate,
and boric acid were obtained from Bio-Scientific Pty. Ltd. The nickel foam was obtained
from Changsha Lyrun Company (China).
Preparation of hierarchical nickel/nickel foam (HNNF)
In the first step of the electrochemical deposition, the electrolyte consisted of 0.1 M NiCl2
and 2 M NH4Cl. A piece of clean nickel foam (NF) acted as the working electrode, and a Pt
plate acted as the counter electrode. The electrochemical deposition was carried out under the
constant current density of 2 A cm-2 for 320 s. In the second step of the electrochemical
deposition, the electrolyte for electrodeposition consisted of 0.85 M NiCl2, 1.5 M
ethylenediamine hydrochloride, and 0.5 M H3BO3. The electrochemical deposition was
carried out under the constant current density of 0.1 A cm-2 for 1080 s.
Preparation of Co(OH)2/HNNF
The electrolyte for electrochemical deposition of Co(OH)2 consisted of 0.35 M
Co(NO3)2·6H2O and 0.12 M NaNO3. The HNNF acted as the working electrode, and a Pt
plate acted as the counter electrode. The electrochemical deposition was carried out under a
constant current density of 3 mA cm-2 for 600 s, and the mass loading was about 2.3 mg cm-2.
To allow comparison with a Co(OH)2/nickel foam electrode (Co(OH)2/NF), the direct
electrochemical deposition of Co(OH)2 on nickel foam was carried out under the same
experimental conditions, and the mass loading was about 2.2 mg cm-2.
Materials Characterization
Scanning electron microscope (SEM) images were collected with a field-emission scanning
electron microscope (FESEM, JEOL-7500, 2 keV). X-ray diffraction (XRD) patterns were
collected on a polycrystalline X-ray diffractometer (RIGAKU, D/MAX 2550 VB/PC, 40
kV/20 mA, λ = 1.5406 Å). Transmission electron microscope (TEM) images and highresolution TEM (HRTEM) images were collected on a transmission electron microscope
(JEOL-2100F, 200 keV).
Electrochemical performance measurements
The electrochemical performance of the as-prepared electrode was measured using cyclic
voltammetry (CV), galvanostatic charge/discharge (GCD) testing, and electrochemical
impedance spectroscopy (EIS) on an electrochemical workstation (VMP-3) with a typical
three-electrode system working at ambient temperature. Specifically, the Co(OH)2/HNNF
and Co(OH)2/NF electrodes were used as the working electrodes, respectively, platinum plate
was used as the counter electrode, and saturated calomel electrode (SCE) was used as the
reference electrode. EIS testing was performed in the frequency range from 100 kHz to 10
mHz at open circuit potential. 2.0 M KOH solution was used as the electrolyte. The areaspecific capacitance was calculated according to the following equation:
CA = I × ∆t / (∆V × S)
(1)
Where CA is the area-specific capacitance (F cm-2), I is the discharging current (A cm-2), ∆t is
the discharging time (s), ∆V is the discharging potential range (V), and S is the electrode area
(cm2), respectively.
Fig. S1 Comparative mechanical strength test. Tape was made to adhere to Ni samples after one-step
and two-step electrochemical deposition (HNNF) (a), and the tape was then peeled off from the Ni samples
(b). There was no obvious residue on the peeled-off tape from the Ni sample after the two-step
electrochemical deposition.
Fig. S2 Comparison of the morphologies of commercial nickel foam and nickel/nickel foam from
two-step electrochemical deposition (HNNF). SEM images of commercial nickel foam (a) and
nickel/nickel foam (HNNF) from two-step electrochemical deposition (b).
Fig. S3 Characterization of HNNF. XRD pattern of HNNF (a), TEM image of HNNF (b), with the inset
showing a piece of nickel flake, SAED pattern of HNNF (c), and HRTEM image of HNNF (d).
Fig. S4 Optical images of NF, HNNF, Co(OH)2/HNNF, and Co(OH)2/NF (from left to right).
Table S1 This work compared with previous reports on free-standing Co(OH)2 and other metal
hydroxide/oxide materials as supercapacitor electrode fabricated by electrochemical deposition.
Material
Current collector
fabrication method
Active material
fabrication method
Active
material
mass loading
(mg cm-2)
Area-specific
capacitance
(F cm-2)
Rate
capability
Cycling
performance
Ref.
Co(OH)2/Ni/Ni foam
Cathodic coelectrochemical deposition
of Ni-Cu, and then
electrochemically
dissolving Cu
Cathodic
electrochemical
deposition
0.50
1.53
(0.25 mA cm-2)
70.69%
(15 mA cm-2)
1.08 F cm-2
About 100%
(2000 cycles,
2.5 mA cm-2)
S1
Co(OH)2/ITO/Ti foil
Chemical vapour
deposition
Cathodic
electrochemical
deposition
0.25
0.51
(0.25 mA cm-2)
74.46%
(5 mA cm-2)
0.38 F cm-2
About 91.5%
(1200 cycles, 0.252.5 mA cm-2)
S2
Co(OH)2/Ni/Ni
foil
Cathodic coelectrochemical deposition
of Ni-Cu, and then
electrochemically
dissolving Cu
Cathodic
electrochemical
deposition
0.024
0.06
(5 mV s-1)
93.2%
(200 mV s-1)
0.056 F cm-2
About 150%
(5 mV s-1)
S3
0.55
0.199
(0.2 mA cm-2)
56.78%
(2 mA cm-2)
0.11 F cm-2
1
2.0
(2 mA cm-2)
95%
(40 mA cm-2)
1.9 F cm-2
0.025
0.071
(0.5 mA cm-2)
96%
(200 mV s-1)
0.056 F cm-2
0.75
1.14
(0.75 mA cm-2)
80%
(7.5 mA cm-2)
0.91 F cm-2
0.75
1.10
(0.75 mA cm-2)
83.4%
(15 mA cm-2)
0.91 F cm-2
73.5 %
(6 mA cm-2)
0.49 F cm-2
Co(OH)2/TiO2/FTO
Hydrothermal reaction
Cathodic
electrochemical
deposition
100%
(2000 cycles,
2 mA cm-2)
S4
Co(OH)2/Ni/Ni
foil
Cathodic
electrochemical deposition
Cathodic
electrochemical
deposition
94.9%
(2000 cycles, 2 mA
cm-2)
S5
Co(OH)2/Cu/Ni foil
Cathodic coelectrochemical deposition
of Ni-Cu, and then
electrochemically
dissolving Cu
Cathodic
electrochemical
deposition
100%
(2000 cycles,
0.5 mA cm-2)
S6
-
Cathodic
electrochemical
deposition
71%
(1000 cycles,
7.5 mA cm-2)
S7
-
Cathodic
electrochemical
deposition
87%
(2000 cycles,
7.5 mA cm-2)
S8
Co-Ni mixed
hydroxide/Ni foam
-
Cathodic coelectrochemical
deposition
0.12
0.36
(0.24 mA cm-2)
94%
(2000 cycles,
2.4 mA cm-2)
S9
Ni(OH)2/Ni foam
-
Cathodic
electrochemical
deposition
0.5
1.58
(2 mA cm-2)
9%
(8 mA cm-2)
0.14 F cm-2
48%
(3000 cycles,
2 mA cm-2)
S10
Ni(OH)2/graphene/
Ni foam
Chemical vapour
deposition
Cathodic
electrochemical
deposition
0.43
0.95
(0.99 mA cm-2)
58.91%
(9.9 mA cm-2)
0.56 F cm-2
77%
(2000 cycles,
9.9 mA cm-2)
S11
Ni(OH)2/ITO/Ti foil
Chemical vapour
deposition
Cathodic
electrochemical
deposition
0.47
0.48
(0.47 mA cm-2)
83.51%
(9.4 mA cm-2)
0.40 F cm-2
93%
(500 cycles,
0.47 mA cm-2)
S12
Co3O4/Ni foam
Chemical vapour
deposition
Cathodic
electrochemical
deposition
1.4
1.91
(2.8 mA cm-2)
54.78%
(28 mA cm-2)
1.05 F cm-2
99%
(3000 cycles,
11.2 mA cm-2)
S13
NiCo2O4/Ni foam
-
Cathodic coelectrochemical
deposition
0.8
1.6
(1.6 mA cm-2)
72%
(16 mA cm-2)
1.15 F cm-2
94%
(2300 cycles,
1.6 mA cm-2)
S14
NiCo2O4/CNT/
stainless steel
Chemical vapour
deposition
Cathodic coelectrochemical
deposition
0.62
0.43
(0.62 mA cm-2)
82.87%
(12.4 mA cm-2)
0.36 F cm-2
91%
(1500 cycles,
2.48 mA cm-2)
S15
Co(OH)2/Ni/Ni foam
Cathodic electrochemical
deposition
Cathodic
electrochemical
deposition
3.17
(5 mA cm-2)
89.59%
(30 mA cm-2)
2.84 F cm-2
303.47%
(2000 cycles,
5 mA cm-2)
9.62 F cm-2
This
work
Co-Ni mixed
hydroxide/Ni foam
Co-Ni mixed
hydroxide/Ni foam
2.30
Figure S5 TEM image of Co(OH)2/HNNF after 2000 cycles (a) and corresponding EDX spectrum
with inset analysis (b).
Figure S6 SEM images (a and b) and HRSEM image (c) of Co(OH)2/HNNF after 1000 cycles.
Figure S7 Further cycling performance testing for the Co(OH)2/HNNF after 2000 cycles under
5 mA cm-2.
Table S2 The Co(OH)2/HNNF after 2000 cycles compared with previous reports on free-standing
electrode with high area-specific capacitance fabricated by hydrothermal reaction.
Materials
Current collector
Area-specific
capacitance
(F cm-2)
Rate capability
Cycling
performance
Ref.
Ni-Co mixed
hydroxide
Ni foam
8.05
(3 mA cm-2)
83%
(30 mA cm-2)
6.68 F cm-2
95%
(15 mA cm-2)
1000 cycles
S16
Ni(OH)2
Ni foam
7.85
(5 mA cm-2)
43%
(30 mA cm-2)
3.38 F cm-2
96%
(30 mA cm-2)
500 cycles
S17
Co(OH)2
Ni foam
1.96
(7mA cm-2)
69%
(28 mA cm-2)
1.35 F cm-2
88%
(7 mA cm-2)
3000 cycles
S18
Co3O4@ NiCo2O4
Ni foam
1.5
(10 mA cm-2)
50%
(30 mA cm-2)
0.75 F cm-2
87%
(7 mA cm-2)
1500 cycles
S19
CoO@ppy
Ni foam
2.51
(5 mA cm-2)
71%
(20 mA cm-2)
1.78 F cm-2
100%
(20 mA cm-2)
2000 cycles
S20
NiCo2O4@NiMoO4
Ni foam
3.74
(2 mA cm-2)
66%
(30 mA cm-2)
2.47 F cm-2
83.1 %
(5 mV s-1)
2000 cycles
S21
Co3O4
Ni foam
4.9
(5 mA cm-2)
51.22%
(30 mA cm-2)
2.51 F cm-2
90 %
(30 mA cm-2)
2000 cycles
S22
Co3O4@Co3O4
Ni foam
5.44
(5 mA cm-2)
69%
(30 mA cm-2)
F cm-2
92 %
(20 mA cm-2)
1000 cycles
S23
NiMoO4@Ni(OH)2
Ni foam
7.43
(4 mA cm-2)
65%
(32 mA cm-2)
3.75 F cm-2
72 %
(8 mA cm-2)
1000 cycles
S24
NiCo2S4@ppy
Ni foam
9.781
(5 mA cm-2)
49%
(30 mA cm-2)
4.79 F cm-2
85%
(50 mA cm-2)
1000 cycles
S25
Co(OH)2/HNNF
after 2000 cycles
HNNF
9.62
(5 mA cm-2)
72%
(30 mA cm-2)
6.93 F cm-2
92%
(5 mA cm-2)
1000 cycles
This work
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