Supporting Information
Dendritic Heterojunction Nanowire Arrays for High-Performance Supercapacitors
Rujia Zou 1,2, Zhenyu Zhang1, Muk Fung Yuen1, Junqing Hu2, Chun-Sing Lee1 & Wenjun
Zhang1
1
Center of Super-Diamond and Advanced Films (COSDAF), Department of Physics and
Materials Science, City University of Hong Kong, Hong Kong, 2 State Key Laboratory for
Modification of Chemical Fibers and Polymer Materials, College of Materials Science and
Engineering, Donghua University, Shanghai 201620, China.
Correspondence and requests for materials should be addressed to J. Q. H.
( hu.junqing@dhu.edu.cn) or W.J. Z. (apwjzh@cityu.edu.hk)
Figure S1. As-synthesized NiCo-precursor nanowires arrays on Ni foam.
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Figure S2. (a) TEM and (b) HRTEM images of NiCo2S4 hollow nanowires.
Figure S3. shows the XRD pattern of NiCo2S4 hollow nanowires on Ni foam. The diffraction
peaks at 44.5º and 51.8º have the same diffracted angle as the (111) and (200) plane
diffraction of Ni (JCPDS 04-0850). The diffraction peaks at 31.6º, 38.3º, 47.4º, 50.5º and
55.3º are corresponding to the (311), (400), (422), (511), and (440) planes of the
nanostructured cubic type NiCo2S4 (JCPDS 20-0782), respectively. The diffraction peaks at
29.9º and 52.1º have the same diffracted angle as the (311) and (440) plane of Co9S8 (JCPDS
65-6801), which can further confirm that the substitution of Co ions by Ni ions only slightly
changes the lattice parameters while keeps the crystal structure1,2.
2
Figure S4. (a) TEM and (b) HRTEM images of NiCo2O4 branched nanowires grown on the
NiCo2S4 hollow nanowires array.
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I. Detailed structural characterizations about as-grown NiCo2S4@NiCo2O4 CSH arrays
Figure S3 shows the as-synthesized NiCo2S4@NiCo2O4 CSH. Figure S5a shows the
typical SEM image that dense NiCo2O4 nanosheets were packed around the NiCo2S4
nanowire cores, forming a typical core-shell heterostructure. The surface of NiCo2S4
nanowires are tightly bonded and totally covered the ultrathin NiCo2O4 nanosheets (< 10 nm),
which stretch out about 500 nm, and the NiCo2O4 nanosheets are interconnected with each
other, as shown in Figure S5b. The magnified image of inset Figure S5b clearly show that
mesopores are uniformly distributed throughout the entire NiCo2O4 shells, whose size is
estimated to be in the range of 2-5 nm. As seen from the HRTEM image in Figure S5c, the
lattice fringes give an interplanar spacing of 0.24 nm, corresponding to that of the (001) lattice
planes of the NiCo2O4 crystal. Therefore, these results obviously demonstrate that
NiCo2S4@NiCo2O4 CSH arrays on Ni foam were synthesized.
Figure S5. (a) SEM images of NiCo2O4@NiCo2S4 CSH arrays. (b) TEM and (c) HRTEM
images of NiCo2O4@NiCo2S4 CSH arrays; inset (b) shown high-magnification TEM image of
NiCo2O4 shell.
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Figure S6. (a) CV curves at different scan rates recorded from electrodes consisting of
NiCo2S4/NiCo2O4 DH electrode. (b) The relationship between anodic peak current versus scan
rate.
Figure S7. SEM images of the NiCo2S4@NiCo2O4 DH, NiCo2S4@NiCo2O4 CSH and
NiCo2S4 nanowires after 3000 cycles at the scan rate of 50 mV/s.
Figure S8. TEM images showing the structural characteristics of (a) DH and (b) CSH
electrodes.
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II. Detailed structural characterizations about as-grown NiCo2S4/NiO, NiCo2S4/Co3O4,
NiCo2S4/MnO2 DH arrays.
Figure S9a reveal that the NiO branched nanowires were distributed evenly along the
NiCo2S4 nanowire, forming NiCo2S4/NiO DH arrays. The NiO branched nanowires have a
diameter of in the range of 20-30 nm and the length of NiO nanowires ranges from 1 to 2 µm.
The NiO branched nanowires have a mesoporous structure with the pore size ranging from 2
to 5 nm (inset Figure S9a). As seen from the HRTEM image in Figure S6d, the lattice fringes
give an interplanar spacing of 0.24 nm and 0.21 nm, corresponding to that of the (111) and
(200) lattice planes of the NiO crystal, which consistent with lattice planes of the NiO in
JCPDS card (No.04-0835).
Figure S9b reveal that the Co3O4 branched nanowires were distributed evenly along
the NiCo2S4 nanowire length, forming NiCo2S4/Co3O4 DH arrays. The Co3O4 branched
nanowires have a diameter of ~ 20 nm and the length of Co3O4 nanowires ranges from 2 to 3
µm. The Co3O4 branched nanowires have a mesoporous structure with the pore size ranging
from 2 to 5 nm (inset Figure S9b). As seen from the HRTEM image in Figure S9e, the lattice
fringes give an interplanar spacing of 0.28 nm and 0.24 nm, corresponding to that of the (220)
and (311) lattice planes of the Co3O4 crystal, which consistent with lattice planes of the Co3O4
in JCPDS card (No.42-1467).
Figure S9c reveal that the MnO2 branched nanowires were distributed evenly along the
NiCo2S4 nanowire length, forming NiCo2S4/MnO2 DH arrays. The Co3O4 branched nanowires
have a diameter of ~20 nm and the length of MnO2 nanowires ranges from 200 to 300 nm. As
seen from the HRTEM image in Figure S9f, the lattice fringes give an interplanar spacing of
0.25 nm and 0.24 nm, corresponding to that of (200) and (-111) lattice planes of Co3O4 crystal,
which consistent with lattice planes of the MnO2 in JCPDS card (No. 80-1098).
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Figure S9. TEM and HRTEM images of as-grown (a and d) NiCo2S4/NiO, (b and e)
NiCo2S4/Co3O4, (c and f)NiCo2S4/MnO2 DH arrays; inset (a and b) shown high-magnification
TEM image of NiO and Co3O4 branched nanowires.
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III. Detailed structural characterizations about as-grown NiCo2S4@NiO,
NiCo2S4@Co3O4, NiCo2S4@MnO2 CSH arrays.
Figure S10a show TEM image of the as-synthesized NiCo2S4@NiO CSH. Dense NiO
nanosheets were packed around the NiCo2S4 nanowire cores, forming a typical core-shell
heterostructure. The surface of NiCo2S4 nanowires are tightly bonded and totally covered by
ultrathin NiO nanosheets (< 20 nm), which stretch out about 500 nm, and the NiO nanosheets
are interconnected with each other. The magnified image of inset Figure S10b clearly show
that mesopores are uniformly distributed throughout the entire NiO shells, whose size is
estimated to be in the range of 2-5 nm. As seen from the HRTEM image in Figure S10d, the
lattice fringes give an interplanar spacing of 0.24 nm, corresponding to that of the (111) lattice
planes of the NiO crystal, which consistent with lattice planes of the NiO in JCPDS card
(No.04-0835).
Figure S10b shows TEM image of the as-synthesized NiCo2S4@Co3O4 CSH. Dense
Co3O4 nanosheets were packed around the NiCo2S4 nanowire cores, forming a typical
core-shell heterostructure. The surface of NiCo2S4 nanowires are tightly bonded and totally
covered the ultrathin Co3O4 nanosheets (< 10 nm), which stretch out about 500 nm, and the
Co3O4 nanosheets are interconnected with each other. The magnified image of inset Figure
S10b clearly shows that mesopores are uniformly distributed throughout the entire Co3O4
shells, whose size is estimated to be in the range of 2-5 nm. As seen from the HRTEM image
in Figure S10e, the lattice fringes give an interplanar spacing of 0.28 nm, corresponding to
that of (220) lattice planes of the Co3O4 crystal, which is consistent with lattice planes of the
Co3O4 in JCPDS card (No.42-1467).
Figure S10c shows TEM image of the as-synthesized NiCo2S4@MnO2 CSH. Dense
MnO2 nanosheets were packed around the NiCo2S4 nanowire cores, forming a typical
core-shell heterostructure. The surface of NiCo2S4 nanowires are tightly bonded and totally
covered by the ultrathin MnO2 nanosheets (< 10 nm), which stretch out about 500 nm, and the
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Co3O4 nanosheets are interconnected with each other. As seen from the HRTEM image in
Figure S10f, the lattice fringes give an interplanar spacing of 0.24 nm, corresponding to that
of (-111) lattice planes of the MnO2 crystal, which is consistent with lattice planes of the
MnO2 in JCPDS card (No.80-1098).
Figure S10. TEM and HRTEM images of as-grown (a and d) NiCo2S4@NiO, (b and e)
NiCo2S4@Co3O4, (c and f) NiCo2S4@MnO2 CSH arrays; inset (a and b) shown
high-magnification TEM image of NiO and Co3O4 shell.
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Figure S11. (a) XRD patterns of as-grown NiCo2S4/NiO DH arrays (i) and NiCo2S4@NiO
CSH arrays (ii). The diffraction peaks at 37.3º, 43.3º and 62.9º are corresponding to the (111),
(200) and (220) planes of NiO (JCPDS 04-0835), respectively. (b) XRD patterns of as-grown
NiCo2S4/Co3O4 DH arrays (i) and NiCo2S4@Co3O4 CSH arrays (ii). The diffraction peaks at
31.3º, 36.9º and 44.8º are corresponding to the (220), (311) and (400) planes of the type
Co3O4 (JCPDS 42-1467), respectively. (c) XRD patterns of as-grown NiCo2S4/MnO2 DH
arrays (i) and NiCo2S4@MnO2 CSH arrays (ii). The diffraction peaks at 25.2º, 37.3º and 42.6º
are corresponding to the (002), (-111) and (-112) planes of the type MnO2 (JCPDS 80-1098),
respectively.
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Figure S12. CV curves at 10 mVs-1 scan rates recorded from electrodes consisting of
NiCo2S4/MnO2, NiCo2S4/NiO, NiCo2S4/Co3O4 DH and NiCo2S4@MnO2, NiCo2S4@NiO,
NiCo2S4@Co3O4 CSH arrays.
Figure S13. (a) Discharge curves of NiCo2S4/MnO2, NiCo2S4/NiO, NiCo2S4/Co3O4 DH and
NiCo2S4@MnO2, NiCo2S4@NiO, NiCo2S4@Co3O4 CSH arrays electrodes at 10 mA cm-2. (b)
Capacitance retention of NiCo2S4/MnO2, NiCo2S4/NiO, NiCo2S4/Co3O4 DH and
NiCo2S4@MnO2, NiCo2S4@NiO, NiCo2S4@Co3O4 CSH arrays electrodes during 3000 cycles
at 50 mVs-1.
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IV. Growth of NiCo2S4/NiCo2O4, NiCo2S4/NiO, NiCo2S4/Co3O4, NiCo2S4/MnO2 BNH and
the NiCo2S4@NiCo2O4, NiCo2S4@NiO, NiCo2S4@Co3O4, NiCo2S4@MnO2 CSH arrays
on Ni foam.
Growth of NiCo2S4/NiCo2O4 DH and NiCo2S4@NiCo2O4 CSH arrays on Ni foam: The
NiCo2S4/NiCo2O4 DH arrays and NiCo2S4@NiCo2O4 CNH arrays on Ni foam were
synthesized using hydrothermal reaction combined with a simple post annealing process. The
NiCo-precursor nanowires arrays are uniformly grown on the Ni foam using a hydrothermal
reaction, as our previously reported3. In a typical synthesis, 1.185g of CoCl2·6H2O, 0.657g of
NiCl2·6H2O and 4.50g urea were dissolved into 40 mL H2O to form a clear pink solution,
which was transferred into a 50 mL Teflon autoclave. The Ni foam substrates were immersed
in a 2 M HCl solution for ~ 10 min to get rid of the possible surface oxide layer, and
transferred into autoclave in an electric oven at 140 ˚C for 8 h. The Ni foam was taken out
from Teflon autoclave after the solution had been cooled down to room temperature and then
cleaned by ultrasonication to remove the loosely attached products on the surface. Then, the
NiCo2S4 hollow nanowire arrays were obtained by placing NiCo2O4-precursor nanowire
arrays on Ni foam and Na2S·9H2O (0.12 g) into a 50 mL autoclave in an electric oven at 110
˚C for 12 h4. The load weight of NiCo2S4 hollow nanowires arrays is about 1.7 mg cm-2.
Subsequently, the NiCo2S4 hollow nanowire arrays on Ni foam were mixed with deionized
water (30 mL), ethanol (15 mL), Co(NO3)2·6H2O (0.34g), Ni(NO3)2·6H2O (0.17g) and
C6H12N4 (0.28g), and the resulting solution was placed in a 50 mL Teflon-lined autoclave.
The autoclave is heated to 150 ˚C for 24 h to obtain NiCo2S4/NiCo2O4-precursor DH arrays on
Ni foam and heated to 150 ˚C for 8 h to obtain NiCo2S4@NiCo2O4-precursor CSH arrays on
Ni foam. The as-obtained product was washed successively with deionized water and ethanol
to remove any residual ionic species, and finally dried in vacuum for 24 h. Finally, in order to
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get crystallized NiCo2S4/NiCo2O4 DH arrays and NiCo2S4@NiCo2O4 CSH arrays on Ni foam
with the as-grown precursor were annealed in Ar gas at 300 °C for 2 h with a heating rate of
0.5 °C min. The load weight of NiCo2S4/NiCo2O4 DH arrays and NiCo2S4@NiCo2O4 CSH
arrays is about 2.7 mg cm-2 and 3.0 mg cm-2.
Growth of NiCo2S4/NiO DH and NiCo2S4@NiO CSH arrays on Ni foam: The
NiCo2S4/NiO DH arrays and NiCo2S4@NiO CSH arrays on Ni foam were also synthesized
using hydrothermal reaction combined with a post annealing process. In a typical synthesis,
the NiCo2S4 hollow nanowire arrays on Ni foam were mixed with deionized water (40 mL),
NiCl2·6H2O (0.17g) and urea (0.30g), and the resulting solution was placed in a 50 mL
Teflon-lined autoclave. The autoclave is heated to 110 ˚C for 24 h to obtain
NiCo2S4/NiO-precursor DH arrays on Ni foam. Besides, the NiCo2S4 hollow nanowire arrays
on Ni foam were mixed with deionized water (40 mL), Ni(NO3)2·6H2O (0.34g) and urea
(0.10g), and the resulting solution was placed in a 50 mL Teflon-lined autoclave. The
autoclave is heated to 100 ˚C for 8 h to obtain NiCo2S4@NiO-precursor CSH arrays on Ni
foam. The as-obtained products were washed successively with deionized water and ethanol
to remove any residual ionic species, and finally dried in vacuum for 24 h. Finally, in order to
get crystallized NiCo2S4/NiO DH arrays and NiCo2S4@NiO CSH arrays on Ni foam, the Ni
foams with the as-grown precursor were annealed in Ar gas at 300 °C for 2 h with a heating
rate of 0.5 °C min. The load weight of NiCo2S4/NiO DH arrays and NiCo2S4@NiO CSH
arrays is about 2.9 mg cm-2 and 2.6 mg cm-2.
Growth of NiCo2S4/Co3O4 DH and NiCo2S4/Co3O4 CSH arrays on Ni foam: The
NiCo2S4/Co3O4 DH arrays and NiCo2S4@Co3O4 CSH arrays on Ni foam were also
synthesized using hydrothermal reaction combined with a post annealing process. In a typical
synthesis, the NiCo2S4 hollow nanowire arrays on Ni foam were mixed with deionized water
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(40 mL), NiCl2·6H2O (0.16g) and urea (0.30g), and the resulting solution was placed in a 50
mL Teflon-lined autoclave. The autoclave is heated to 110 ˚C for 24 h to obtain
NiCo2S4/Co3O4-precursor DH arrays on Ni foam. Besides, the NiCo2S4 hollow nanowire
arrays on Ni foam were mixed with deionized water (40 mL), NiCl2·6H2O (0.56g) and urea
(0.10g), and the resulting solution was placed in a 50 mL Teflon-lined autoclave. The
autoclave heated to 100 ˚C for 8 h to obtain NiCo2S4@Co3O4-precursor CSH arrays on Ni
foam. The as-obtained product was washed successively with deionized water and ethanol to
remove any residual ionic species, and finally dried in vacuum for 24 h. Finally, in order to
get crystallized NiCo2S4/Co3O4 DH arrays and NiCo2S4@Co3O4 CSH arrays on Ni foam, the
Ni foams with the as-grown precursor were annealed in Ar gas at 300 °C for 2 h with a
heating rate of 0.5 °C min. The load weight of NiCo2S4/Co3O4 DH arrays and
NiCo2S4@Co3O4 CSH arrays is about 3.2 mg cm-2 and 2.8 mg cm-2.
Growth of NiCo2S4/MnO2 DH and NiCo2S4/MnO2 CSH arrays on Ni foam: The
NiCo2S4/MnO2 DH arrays and NiCo2S4@MnO2 CSH arrays on Ni foam were also synthesized
using hydrothermal reaction combined with a post annealing process. In a typical synthesis,
the NiCo2S4 hollow nanowire arrays on Ni foam were mixed with deionized water (40 mL)
and KMnO4 (0.16g), and the resulting solution was placed in a 50 mL Teflon-lined autoclave.
The autoclave is put into 180 ˚C oven for 2 h to obtain NiCo2S4/MnO2 DH arrays on the Ni
foam. Besides, the NiCo2S4 hollow nanowire arrays on the Ni foam were mixed with
deionized water (40 mL) and KMnO4 (0.32g), and the resulting solution was placed in a 50
mL Teflon-lined autoclave. The autoclave is heated to 160 ˚C for 30 min to obtain
NiCo2S4@MnO2 CSH arrays on Ni foam5. The as-obtained products were washed
successively with deionized water and ethanol to remove any residual ionic species, and
finally dried in vacuum for 24 h. Finally, in order to get well crystallized NiCo2S4/MnO2 DH
arrays and NiCo2S4@MnO2 CSH arrays on Ni foam, the Ni foams with the as-grown
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precursor were annealed in Ar gas at 250 °C for 2 h with a heating rate of 0.5 °C min. The
load weight of NiCo2S4/MnO2 DH arrays and NiCo2S4@MnO2 CSH is about 2.8 mg cm-2 and
2.7 mg cm-2.
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nickel foam for aqueous asymmetric supercapacitors. J. Mater. Chem. A 2, 4795 (2014).
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