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Facile synthesis of 3D gem shape Co3O4 with mesoporous structure as electrode for high-performance supercapacitors
Journal of Alloys and Compounds xxx (xxxx) xxx
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Facile synthesis of 3D gem shape Co3O4 with mesoporous structure as electrode for high-performance supercapacitors Hongmei Chen a, Chenyang Xue a, **, Zhenyin Hai b, c, Danfeng Cui a, Maoxing Liu d, e, Yuankai Li a, Wendong Zhang a, * a
Science and Technology on Electronic Test and Measurement Laboratory, North University of China, Taiyuan, Shanxi, 030051, China Center for Environmental & Energy Research, Ghent University Global Campus, Incheon 21985, South Korea Department of Solid State Sciences, Ghent University, Ghent, 9000, Belgium d Department of Mathematics, North University of China, Taiyuan, 030051, China e Department of Mathematics, Qingdao University of Science and Technology, Qingdao, 266061, China b c
a r t i c l e i n f o
a b s t r a c t
Article history: Received 23 July 2019 Received in revised form 28 October 2019 Accepted 6 November 2019 Available online xxx
In this work, a 3D gem shape Co3O4 nanomaterial using nickel foam (Ni foam) as substrate was synthesized as supercapacitor electrode. The morphology and structures of the Co3O4 were characterized by various test-methods including XRD, BET, FTIR, TG, SEM, TEM and XPS. The fabricated Co3O4 nanomaterial achieved an excellent capacitance of 1060.0 F g1 at 1 A g1 and a super-long cycling life with 99.6% retention rate after 5000 cycles at 8 A g1. Moreover, the as-fabricated Co3O4//AC supercapacitor, with the as-prepared Co3O4 as positive electrode and the activated carbon as negative electrode, delivered a high energy density (44.99 Wh kg1) at the power density of 0.2 kW kg1. The superior performances were mainly due to the high specific surface area, the suitable pore structure, and the uniformed 3D “gem shape” morphology of the Co3O4 nanomaterials. This work is of great significance to the development of high-performance energy storage devices and even to other application fields such as photocatalysis and sensors. © 2019 Elsevier B.V. All rights reserved.
Keywords: Co3O4 Gem shape Hydrothermal Supercapacitor
1. Introduction Our daily life depends heavily on electricity energy. At present, fossil fuel is the main energy source for human production and living. With the growth of global energy consumption, nonrenewable energy sources such as fossil fuels will be ultimately exhausted in the near future, which will have a serious impact on the environment [1]. Thus, the development of new types of clean and efficient energy storage technology has attracted more and more attentions in both academia and industry. Supercapacitors have led to extensive researches because they possess many advantages including high power density and low cost [2e4]. Recently, various transition-metal oxides were extensively explored and applied in the supercapacitors, such as NiO [5], NiCo2O4 [6,7], RuO2 [8], Co3O4 [9e11], MnO2 [12e14] and ZnO [15].
* Corresponding author. ** Corresponding author. E-mail addresses: [email protected] (C. Xue), [email protected] (W. Zhang).
Co3O4, as a transition metal oxide with spinel structure and a ptype semiconductor, has attracted great attentions in many fields such as supercapacitors [16], sensors [17] photocatalysis [18] due to the high theoretical capacitance (3560 F g1), low cost, natural abundance, and the appropriate band gap energy (2.1eV). In the application for supercapacitors, over the past decade, Co3O4 materials have attracted high research interests in obtaining excellent electrochemical performances. For example, Wang et al. [19] revealed that the crater-like Co3O4 delivered a capacitance of 102 F g1 and the capacitance can keep 74% after 500 cycles. Meng et al. [20] reported that the Co3O4 nanorods showed a specific capacity of 262 F g1 at 5 mV/s. The needle-like Co3O4 nanorods with the highest capacitance of 111 F g1 and 88.2% capacitance retention after 1000 cycles were reported [21]. Cao et al. [22] reported the Co3O4 hollow octahedra with a charge storage capacitance of 192 F g1. Although some progress on the Co3O4 electrode materials has been made, there are still some drawbacks, which limit their further practical application, such as low capacitance, low energy density, and poor cycle stability. Hence, it is urgent to fabricate the Co3O4 electrode with higher storage capacity and excellent cycling
https://doi.org/10.1016/j.jallcom.2019.152939 0925-8388/© 2019 Elsevier B.V. All rights reserved.
Please cite this article as: H. Chen et al., Facile synthesis of 3D gem shape Co3O4 with mesoporous structure as electrode for high-performance supercapacitors, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.152939
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stability. Compared to other materials preparation methods, the materials synthesized by hydrothermal method has the advantages of smaller particle size, more uniform size distribution, lighter particle agglomeration, and it is easy to get suitable stoichiometric and crystal shapes. In this work, 3D gem shape Co3O4 with mesoporous structure was synthesized via a hydrothermal process. The physical and chemical structural properties of the Co3O4 were measured. Meanwhile, the electrochemical performance for the Co3O4 nanomaterial was tested in 6.0 M KOH. The Co3O4 electrode showed a high mass capacitance of 1060.0 F g1 at 1 A g1. Besides, the capacitance retention can reach 99.6% after 5000 discharge-charge cycles at 8 A g1. Moreover, the two-electrode device (Co3O4//AC) was fabricated and tested. The highest energy density was 44.99 Wh kg1 at power density of 0.2 kW kg1. 2. Experimental 2.1. Material synthesis The chemical reagents in this paper are analytically pure and used without further purification. Synthesis of Co3O4: The Ni foam substrate was washed by acetone, hydrochloric acid, and deionized water for 15 min, respectively. Then the Ni foam was dried at 70 C. In a typical preparation process of Co3O4, 6 mmol Co(NO3)2$6H2O and 18 mL of deionized water were mixed under vigorous magnetic stirring for 10 min. Then, 12 mL ammonia solution was dropped and stirred for 30 min. Finally, the resulting solution with the Ni foam substrate was transferred into 50 mL stainless steel autoclave and kept for 10 h under 120 C. After the hydrothermal reaction, the obtained precursor was washed with deionized water, dried at 70 C for 5 h, and calcined at 300 C for 2 h at a heating rate of 2 C min1. The Co(OH)2 materials were preparation by sedimentary of (Co(NO)2$6H2O) as shown below: þ CoðNoÞ2 , 6H2 O þ 2NH4 OH / COðOHÞ2 þ 2NOþ 3 þ 2NH4
þ 6H2 O
(1)
The Co3O4 structure was formed by calcinating the as-prepared Co(OH)2 at 300 C shown as below: D,300 C
CoðOHÞ2 þ 1=2O2 !Co3 O4 þ 3H2 O
(2)
tests were all performed over an electrochemical workstation (RST 5000). The three-electrode test was performed with the Co3O4 on the Ni foam as the working electrode, a platinum wire as the auxiliary electrode, and a saturated calomel electrode as the reference electrode. Cyclic voltammetry (CV) test and galvanostatic charge-discharge measurements were carried out to evaluate the electrochemical properties. The mass capacitance was calculated with the following equation:
C¼
I Dt ms DV
(3)
where C is the mass specific capacitance (F g1), I (A) is the discharge current, Dt (s) is the discharge time, ms (g) is active material quality, and DV is the charge and discharge potential difference. The weight of active material was approximately 9.98 mg/ cm2. Moreover, the two-electrode device was fabricated with the Co3O4 as positive and AC as negative electrode. The negative electrode was prepared by mixing AC, acetylene black and PVDF in ethanol with a mass ratio of 8:1:1 using polytetrafluoroethylene (PTFE) as binder. The mass balance of the positive and negative electrodes can be expressed as the following equation [23e25]:
mþ C DV ¼ m Cþ DVþ
(4)
Among which, m, C, and DV stand for the weight of active materials, specific capacitance, and potential window for each electrode, respectively. The “þ” and “” represent the positive and negative electrodes. The weight of Co3O4 and carbon was around 9.98 and 13.2 mg according to the analysis results. The energy density and power density were obtained according to the following equations [26]:
C¼
I Dt mDV
(5)
E¼
C ðDVÞ2 2
(6)
P¼
E t
(7)
where E is the energy density (Wh kg1), P stands for the power density (kW kg1), and C, V, and t are mass capacitance (F g1), potential window (V) and discharge times (h), respectively.
2.2. Material characterizations 3. Results and discussion SEM and TEM measurement were performed with FEI Inspect F50 and FEI Inspect F30. The texture properties were measured by N2 adsorption-desorption isotherms on a NOVA2200e instrument using the pure Co3O4 sample separated from the Co3O4 on Ni foam. The chemical composition of the sample was determined with a D2 Phaser desktop/max-RAX-ray diffractometer (Bruker, Germany) ranging from 15 to 85 . FTIR spectra were recorded on a NEXUS Thermo Nicolet IR-spectrometer. The thermogravimetric test was performed on a PerkinElmer STA 800 instrument from 50 C to 600 C in the air atmosphere and the heating rate was 5 C/min. XPS was carried out on an ESCALAB 250Xi spectrometer. SEM and high HRTEM measurement were performed with FEI Inspect F50 and FEI Inspect F30. 2.3. Performance measurements The three-electrode configuration and the two-electrode system
3.1. Structure and morphology The XRD patterns of the Co3O4 and its precursor were tested to display the phase structure in Fig. 1. The series of diffraction peaks at 2q of 44.51, 51.84 , and 76.39 belonged to (111), (200), and (220) planes of Ni (JCPDS 04-0850). For the precursor, the diffraction peaks at 2q of 19.06 , 37.92 , 38.67 and 57.91 were assigned to the lattice planes of the Co(OH)2 species (JCPDS 30-0443). Moreover, the peaks centered at 2q ¼ 19.01, 36.87, 38.54 , 55.66 , 59.42 , 65.23 were assigned to the lattice planes of Co3O4 from the Co3O4 material (JCPDS 04-0850). The result suggested the successful preparation of Co(OH)2 after the hydrothermal process while the Co3O4 was formed after the calcination of the precursor. The FTIR spectra of the precursor Co(OH)2 and the Co3O4 are shown in Fig. 2a. For the precursor, the peak centered at 3624 cm1 matches well with the OeH stretching vibration of CoeOH group
Please cite this article as: H. Chen et al., Facile synthesis of 3D gem shape Co3O4 with mesoporous structure as electrode for high-performance supercapacitors, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.152939
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Fig. 1. XRD patterns of the precursor Co(OH)2 and the Co3O4.
while the peak at 1630 cm1 belongs to the bending vibration of the absorbed interlayer water molecule, and another peak at around 1386 cm1 is attributed to the n3 vibration of NO 3 , which indicates that nitrate ions may adsorb on the surface of the precursor [27e29]. Besides, the FTIR spectrum of the final Co3O4 is also shown in Fig. 2a, and the two strong peaks at 660 and 570 cm1 correspond to the stretching vibration of Co(2p)-O bond and Co(3p)-O bond, respectively [30e32]. To analyze the thermal behavior of the Co(OH)2 precursor, the thermogravimetric analysis was tested in the air atmosphere as presented in Fig. 2b. The thermogravimetric analysis curve indicated that the decomposition process began at about 170 C and the abrupt change process of the weight inferred the phase change from Co(OH)2 to the Co3O4 [33]. Additionally, about 11.2% weight percentage loss happened in the temperature-programmed process from 50 C to 600 C, which was close to the theoretical value of 13.6%. As presented in Fig. 3a-b, the Ni foam is almost entirely and uniformly covered by the 3D “gem shape” particles. Furthermore, the Co3O4 sample was analyzed by TEM. As displayed in Fig. 3d, the lattice constants of 0.205 and 0.214 nm are corresponded to the dspacing of (311) and (222) respectively, and the results are in line
3
with the XRD results. Meanwhile, the energy dispersive spectrometer mapping (EDS) of the Co3O4 was test to analyze the distribution of Co and O (Fig. 3e) and the results revealed that the Co and O elements were successfully scattered on the Ni foam substrate. The N2-adsorption was carried out to explore the pore structure and the surface area. Fig. 4a showed the N2 adsorption-desorption of the Co3O4 nanomaterial and the isotherm was attributed to type-IV. More importantly, the Co3O4 nanomaterial had a large specific surface area of 117.7 m2 g1. Additionally, the pore size distribution of Co3O4 particle was presented in Fig. 4b. The pore size was distributed under 20 nm. Specifically, the pore size and the pore volume were analyzed to be 13.6 nm and 0.069 cc g1 respectively, indicating that the Co3O4 belonged to the mesoporous material. It is well known that the sample morphologies vary greatly due to the different preparation procedures, further leading to diversity in the structure properties including the specific surface area. Due to the unique 3D “gem shape” mesoporous structure of the prepared oxide, a higher surface area of the sample was obtained compared to the other similar materials, such as Co3O4 nanocubes (74.8 m2 g1) [2], Co3O4 crater-like microspheres (60 m2 g1) [19], Co3O4 nanorods (23 m2 g1) [20], 2D Co3O4 nanosheet (27.15 m g1) [26], and even some composite oxides including NiCo2O4 (48.61 m2 g1), NiCo2O4@MnMoO4 (65.25 m2 g1) [6], NiCo2O4 with diamond-shaped hexahedron structure (59.882 m2 g1) [7], ZnOeCo3O4 (53.66 m2 g1) [24], and NiCo2O4@Co3O4 (73.43 m2 g1) [26]. Generally speaking, a high specific area means more electrochemically active sites, which can promote the redox reaction to obtain better electrochemical performance. Hence, the high specific surface area and the suitable pore structure are important factors for the perfect electrochemical performance of the Co3O4 nanomaterial. XPS presented in Fig. 5 were tested in order to identify the surface element composition of the Co3O4. As shown in Fig. 5a, there are two peaks centered at about 795.1 eV and 780.1 eV, which were assigned to the metallic peaks of Co 2p1/2 and Co 2p3/2, respectively [34e36]. Besides, only one peak could be seen from Fig. 5b and the peak located at 530.1 eV was assigned to O1s [37], which conforms with the lattice oxygen in the Co3O4 phase. 3.2. Electrochemical test The cyclic voltammetry (CV) measurements were performed to explore the electrochemical properties of the Co3O4. Fig. 6a shows CV curves of the Co3O4 at different scan rates from 5 to 100 mV/s in the voltage window ranging from 0 to 0.6 V. There are obvious
Fig. 2. (a) FTIR spectra of the Co3O4 and Co(OH)2, and (b) the thermogravimetric analysis curve of the Co(OH)2 sample.
Please cite this article as: H. Chen et al., Facile synthesis of 3D gem shape Co3O4 with mesoporous structure as electrode for high-performance supercapacitors, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.152939
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Fig. 3. (aeb) SEM images, (ced) TEM images and (e) EDS mapping of the Co3O4.
Fig. 4. (a)N2 adsorption-desorption isotherm and (b) the corresponding pore size distribution of Co3O4 particles.
redox peaks on the CV curve of Co3O4 and the results inferred that the capacitance of Co3O4 derives from pseudocapacitance [38,39]. The redox peak in the cyclic voltammetry curve gradually weakened in the three-electrode system with the increase of scanning speed due to the internal resistance of the electrode material itself and between the solution and the electrode. The corresponding oxidation and reduction peaks move to the poles respectively and this phenomenon was due to the polarization effect. With the increase of scanning speed, the cyclic voltammetry curve maintains a good shape, indicating that the Co3O4 material has a good power performance. The faradaic reactions can be described by the following formulas [40,41]: Co3O4 þ OH þ H2O ¼ 3CoOOH þ e
(8)
CoOOH þ OH ¼ 3CoOOH þ H2O þ e
(9)
Fig. 6b shows the galvanostatic discharge results of the Co3O4 at different current densities and the variation trend of mass specific capacitance with current density increasing is shown in Fig. 6c. As presented in Fig. 6c, the mass capacitances of the Co3O4 electrode are 1060.0, 999.7, 947.3, 902.0, 851.3, 720 and 642.5 F g1 at different current densities of 1, 2, 3, 4, 5, 8 and 10 A g1, respectively. The mass capacitances decreased as the current densities increased, and the mass capacitance at 10 A g1 was still 60.6% of that of the capacitance at 1 A g1. The mass capacitance decreasing was mainly because the existence of internal active sites couldn’t completely maintain the redox transition in the case of fast scanning speed [42]. The mass capacitance of the Co3O4 material is much higher than that of the other supercapacitors reported (Table 1). Furthermore, the galvanostatic cycling experiment was performed to investigate the cycling stability of the Co3O4 electrode at a current density of 8 A g1 and the result was shown in Fig. 6d. The Co3O4
Please cite this article as: H. Chen et al., Facile synthesis of 3D gem shape Co3O4 with mesoporous structure as electrode for high-performance supercapacitors, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.152939
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Fig. 5. XPS of (a) Co 2p and (b) O 1s of the Co3O4.
Fig. 6. (a)The CV curves, (b) galvanostatic charge-discharge curves, (c) specific capacitances at different current density, and (d) cycling stability of the composite at the current density of 8 A g1 of the Co3O4.
electrode exhibited good stability with cycling efficiency of 99.6% after 5000 cycles. The fluctuations of capacity retention rate during long cycling experiment may be caused by the temperature variation due to the day and night alternation [43e45]. The electrochemical impedance spectroscopy (EIS) was performed with a frequency range from 0.1 Hz to 10 kHz for the Co3O4 electrode material and Fig. 7a showed Nyquist plots of the Co3O4 electrode along with its fitted curve. Simultaneously, an equivalent circuit was also used to obtain the charge-transfer resistance (Fig. 7b). As seen in Fig. 7a, the Nyquist curve is an arc at high
frequencies and an oblique straight line at low frequencies. The radius of the arc in the high frequency region represents the charge transfer resistance (Rct) and the small arc radius reveals that the resistance of the Co3O4 material is very small. The low-frequency part in the Nyquist curve stands for the Warburg impedance and it was determined by the slope of the line. In the EIS, Rs, C, Rct, Zw stand for the electrolyte resistance, capacitance, charge transfer resistance, Warburg impedance, respectively. Also, Fig. 7a displayed that the fitting curves matched with the EIS curves perfectly and the fitting error was only 1.79 1005 of Co3O4 electrode.
Please cite this article as: H. Chen et al., Facile synthesis of 3D gem shape Co3O4 with mesoporous structure as electrode for high-performance supercapacitors, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.152939
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Table 1 Different electrochemical properties in previous reports for supercapacitors Material
Specific Capacitance (F g1)
current density (A g1)
Capacity Retention//Cycling number
Reference
Co3O4 CWs-Co3O4 Co3O4-0.5/MWCNT Co3O4/N-CP Co3O4 Co3O4 Co3O4/Graphene Co3O4 Co3O4 Co3O4
814 978.9 273 316.2 574 390.4 357 739 384.375 1060
1 0.5 0.5 1 0.1 1 0.5 1 3 1
e 94.6%//2000 88%//500 93%//20000 95%//1000 95%//500 87%//1000 90.2%//1000 96.54%//1000 99.6%//5000
[24] [40] [46] [47] [48] [49] [50] [51] [52] This work
Fig. 7. (a) The Nyquist plots and the fitted plots, and (b) the equivalent circuit diagram of Co3O4 electrode.
Moreover, the Rs, Rct1, Rct2, Zw of the Co3O4 electrode are 0.35 U, 0.85 U, 0.12 U and 1.499, respectively. To further study the practical application of supercapacitor, the Co3O4//AC supercapacitor was assembled and the two-electrode performance was measured using Co3O4 as positive electrode material and AC as negative electrode material. Firstly, the CV curves were investigated to contrast the capacitive performance of Co3O4 and AC electrodes, and the Co3O4 electrode had a higher capacitance (Fig. 8a). Furthermore, the CV and galvanostatic chargedischarge tests for the Co3O4//AC two-electrode system were also measured. From Fig. 8b it can be seen that the CV curve shows an obvious redox peak, indicating that the two-electrode system undergoes redox reaction as the scan rate increases from 30 to 300 mV s1. Additionally, Fig. 8c indicated that the mass capacitances of the Co3O4 electrode were 253.1, 236.7, 167.7, 161.6 and 131.3 F g1 at different current densities of 0.5, 1, 2, 3 and 5 A g1, respectively. Fig. 8d displayed the relationship between specific capacitance and current density. As we can see, the specific capacitance decreased with the current increasing for the similar reason as the performance in the three-electrode system that the faster the scanning rate, the less the redox transition can be maintained by the presence of internal active sites [42]. Furthermore, Fig. 9 showed the energy density and power density of the Co3O4//AC and other reported works. The energy density of Co3O4//AC showed the maximum of 44.99 Wh kg1 at the power density of 0.2 kW kg1, and the energy density still maintained 23.33 Wh kg1 even at the high power density of 2 kW kg1. Moreover, comparisons had been made between our work and other previous works, such as nitrogen-doped carbon aerogel/cobalt oxide (NCA/Co3O4, 33.43 Wh kg1 at the power density of 0.375 kW kg1) [53], Co3O4/three-dimensional graphene
networks/Ni foam (Co3O4/3DGN/NF, 7.5 Wh kg1 at the power density of 0.794 kW kg1) [54], 3D Co3O4-RGO (40.65 Wh kg1 at the power density of 0.34 kW kg1) [55], NiCo2O4@hollow microrod arrays (15.42 Wh/kg at the power density of 0.5 kW kg1) [56], Co3O4/Hollow-Carbon-Fiber (24.31 Wh kg1 at the power density of 0.75 kW kg1) [57], Co3O4/nitrogen-doped carbon hollow sphere (34.5 Wh kg1 at the power density of 0.735 kW kg1) [58], ZneNieCo ternary oxide (35.6 Wh kg1 at the power density of 0.1876 kW kg1) [59], NiCo2O4@MnO2 (35 Wh kg1 at the power density of 0.163 kW kg1) [60], 3D Co3O4@Ni(OH)2 (41.9 Wh kg1 at the power density of 0.0361 kW kg1) [61], Co3O4/AC (24.9 Wh kg1 at the power density of 0.225 kW kg1) [62]. It can be concluded that the results of the energy density and the power density in this work were superior to many other Co3O4 samples and even some composite oxides, suggesting the tremendous application potential of the Co3O4 electrode material. 4. Conclusions In conclusion, the 3D Co3O4 gem shape electrode material with mesoporous structure has been fabricated by a simple hydrothermal method and the corresponding electrochemical properties were tested. The Co3O4 delivered a high mass capacity of 1060.6 F g1 at 1 A g1. Besides, the Co3O4 showed a perfect mass capacity of 717.1 F g1 after 5000 cycles test at 8 A g1, which was about 99.6% of its initial capacitance. Moreover, its maximum energy density was obtained to be 44.99 Wh kg1. Hence, the Co3O4 preparation via our new synthetic route displayed excellent mass capacity and energy density, along with perfect cycling stability. Meanwhile, the prepared Co3O4 material owned obvious crystal structure, excellent crystallinity, high specific surface area and
Please cite this article as: H. Chen et al., Facile synthesis of 3D gem shape Co3O4 with mesoporous structure as electrode for high-performance supercapacitors, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.152939
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Fig. 8. The electrochemical performance of the supercapacitor of Co3O4//AC: (a) CV curves of Co3O4 electrode and AC electrode; (b) CV curves and (c) galvanostatic charge-discharge curves of Co3O4//AC; (d) the specific capacitance at different current density.
Acknowledgments Financial support from the School Foundation for North University of China (Grant No. 110246), Shanxi Science foundation of China(Grant No. 201801D221197), Shanxi Scholarship Council of China (Grant No. 2017-094), Shanxi Scholarship Council of China (Grant No. 2017-094), the National Science Foundation of China (Grant No.61501408), and Shanxi ‘1311 project’ Key Subject Construction(1331KSC) for supporting this work. References
Fig. 9. The energy density and power density of Co3O4//AC and other reported works.
suitable pore structure. Therefore, the Co3O4 material proposed in this work has a good application prospect in the electrode of supercapacitor and it may be a potential candidate in many other research fields such as photocatalysis and sensors.
Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
[1] N. Zhao, L. Kong, Y. Dong, G. Wang, X. Wu, P. Jiang, Insight into the crucial factors for photochemical deposition of cobalt cocatalysts on g-C3N4 photocatalysts, ACS Appl. Mater. Interfaces 10 (2018) 9522e9531. [2] M. Pal, R. Rakshit, A.K. Singh, K. Mandal, Ultra high supercapacitance of ultra small Co3O4 nanocubes, Energy 103 (2016) 481e486. [3] S. Park, S. Kim, Effect of carbon blacks filler addition on electrochemical behaviors of Co3O4/graphene nanosheets as a supercapacitor electrodes, Electrochim. Acta 89 (2013) 516e522. [4] G. Wang, L. Zhang, J. Zhang, A review of electrode materials for electrochemical supercapacitors, Chem. Soc. Rev. 41 (2012) 797e828. [5] M. Liu, J. Chang, J. Sun, L. Gao, Synthesis of porous NiO using NaBH4 dissolved in ethylene glycol as precipitant for high-performance supercapacitor, Electrochim. Acta 107 (2013) 9e15. [6] Y. Chen, Y. Li, Z. Hai, Y. Li, S. Kan, J. Chen, X. Chen, S. Zhuiykov, D. Cui, C. Xue, Facile-synthesized NiCo2O4@MnMoO4 with novel and functional structure for superior performance supercapacitors, Appl. Surf. Sci. 452 (2018) 413e422. [7] Y. Li, X. Hou, Z. Zhang, Z. Hai, H. Xu, D. Cui, S. Zhuiykov, C. Xue, NiCo2O4 particles with diamond-shaped hexahedron structure for high-performance supercapacitors, Appl. Surf. Sci. 436 (2018) 242e251. [8] C. Hu, K. Chang, M. Lin, Y. Wu, Design and tailoring of the nanotubular arrayed architecture of hydrous RuO2 for next generation supercapacitors, Nano Lett. 6 (2006) 2690e2695. [9] V. Srinivasan, J.W. Weidner, Capacitance studies of cobalt oxide films formed via electrochemical precipitation, J. Power Sources 108 (2002) 15e20. [10] W. Du, R. Liu, Y. Jiang, Q. Lu, Y. Fan, F. Gao, Facile synthesis of hollow Co3O4 boxes for high capacity supercapacitor, J. Power Sources 227 (2013) 101e105.
Please cite this article as: H. Chen et al., Facile synthesis of 3D gem shape Co3O4 with mesoporous structure as electrode for high-performance supercapacitors, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.152939
8
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[11] X. Feng, C. Shen, Y. Yu, S. Wei, C. Chen, Synthesis and electrochemical properties of sticktight-like and nanosheet Co3O4 particles, J. Power Sources 230 (2013) 59e65. [12] Z. Huang, Y. Song, D. Feng, Z. Sun, X. Sun, X. Liu, High mass loading MnO2 with hierarchical nanostructures for supercapacitors, ACS Nano 12 (2018) 3557e3567. [13] H. Jia, Y. Cai, X. Zheng, J. Lin, H. Liang, J. Qi, J. Cao, J. Feng, W. Fei, Mesostructured carbon nanotube-on-MnO2 nanosheet composite for highperformance supercapacitors, ACS Appl. Mater. Interfaces 10 (2018) 38963e38969. [14] J. Kang, A. Hirata, L. Kang, X. Zhang, Y. Hou, L. Chen, C. Li, T. Fujita, K. Akagi, M. Chen, Enhanced supercapacitor performance of MnO2 by atomic doping, Angew. Chem. Int. Ed. 52 (2013) 1664e1667. [15] J. Yuan, X. Zhang, C. Chen, Y. Hao, R. Agrawal, C. Wang, W. Li, H. Yu, Y. Yu, X. Zhu, Z. Xiong, Y. Xie, Facile fabrication of three-dimensional porous ZnO thin films on Ni foams for lithium ion battery anodes, Mater. Lett. 190 (2017) 37e39. [16] T. Akamatsu, T. Itoh, N. Izu, W. Shin, Effect of noble metal addition on Co3O4based gas sensors for selective NO detection, Sens. Mater. 28 (2016) 1191e1201. [17] H. Xu, C. Xia, S. Wang, F. Han, M. Karbalaeiakbari, Z. Hai, S. Zhuiykov, Electrochemical non-enzymatic glucose sensor based on hierarchical 3D Co3O4/Ni heterostructure electrode for pushing sensitivity boundary to a new limit, Sens. Actuator B Chem. 267 (2018) 93e103. [18] Q. Zhang, Z. Hai, A. Jian, H. Xu, C. Xue, S. Sang, Synthesis of p-Co3O4/n-TiO2 nanoparticles for overall water splitting under visible light irradiation, Nanomaterials 6 (2016) 138e148. [19] L. Wang, X. Liu, X. Wang, X. Yang, L. Lu, Preparation and electrochemical properties of mesoporous Co3O4 crater-like microspheres as supercapacitor electrode materials, Curr. Appl. Phys. 10 (2010) 1422e1426. [20] T. Meng, Q. Xu, Z. Wang, Y. Li, Z. Gao, X. Xing, T. Ren, Co3O4 Nanorods with self-assembled nanoparticles in queue for supercapacitor, Electrochim. Acta 180 (2015) 104e111. [21] T. Zhu, J. Chen, X. Lou, Shape-controlled synthesis of porous Co3O4 nanostructures for application in supercapacitors, J. Mater. Chem. 20 (2010) 7015e7020. [22] Y. Cao, F. Yuan, M. Yao, J. Bang, J. Lee, A new synthetic route to hollow Co3O4 octahedra for supercapacitor applications, CrystEngComm 16 (2014) 826e833. [23] T. Wang, S. Zhang, X. Yan, M. Lyu, L. Wang, J. Bell, H. Wang, 2methylimidazole-derived Ni-Co layered double hydroxide nanosheets as high rate capability and high energy density storage material in hybrid supercapacitors, ACS Appl. Mater. Interfaces 9 (2017) 15510e15524. [24] M. Gao, W. Wang, Q. Rong, J. Jiang, Y. Zhang, H. Yu, Porous ZnO-coated Co3O4 nanorod as a high-energy-density supercapacitor material, ACS Appl. Mater. Interfaces 10 (2018) 23163e23173. [25] X. Li, Y. Liu, Z. Jin, P. Li, X. Chen, D. Xiao, Enhanced electrochemical performance of C-NiO/NiCo2O4//AC asymmetric supercapacitor based on material design and device exploration, Electrochim. Acta 296 (2019) 335e344. [26] P. Sennu, V. Aravindan, Y.-S. Lee, High energy asymmetric supercapacitor with 1D@2D structured NiCo2O4@Co3O4 and jackfruit derived high surface area porous carbon, J. Power Sources 306 (2016) 248e257. [27] A.-A.M. Barmi, M. Aghazadeh, B. Arhami, H.M. Shiri, A.A. Fazl, E. Jangju, Porous cobalt hydroxide nanosheets with excellent supercapacitive behavior, Chem. Phys. Lett. 541 (2012) 65e69. [28] D. Ghosh, S. Giri, C.K. Das, Preparation of CTAB-assisted hexagonal platelet Co(OH)2/graphene hybrid composite as efficient supercapacitor electrode material, ACS Sustain. Chem. Eng. 1 (2013) 1135e1142. [29] Y. Li, Y. Wu, Critical role of screw dislocation in the growth of Co(OH)2 nanowires as intermediates for Co3O4 nanowire growth, Chem. Mater. 22 (2010) 5537e5542. [30] X. Tong, Z. Hai, D. Cui, L. Gao, Q. Zhang, H. Xu, Y. Ma, C. Xue, J. Liu, Investigation of lattice distortion of Co3O4 nanoparticles prepared by a carbon-assisted method, Microelectron. Eng. 159 (2016) 17e20. [31] Y. Wang, J. Shi, J. Cao, G. Sun, Z. Zhang, Synthesis of Co3O4 nanoparticles via the CTAB-assisted method, Mater. Lett. 65 (2011) 222e224. [32] S. Dubey, J. Kumar, A. Kumar, Y.C. Sharma, Facile and green synthesis of highly dispersed cobalt oxide (Co3O4) nanopowder: characterization and screening of its eco-toxicity, Adv. Powder Technol. 29 (2018) 2583e2590. [33] B. Wang, X. Lu, Y. Tang, Synthesis of snowflake-shaped Co3O4 with a high aspect ratio as a high capacity anode material for lithium ion batteries, J. Mater. Chem. 3 (2015) 9689e9699. [34] H. Sun, X. Sun, T. Hu, M. Yu, F. Lu, J. Lian, Graphene-wrapped mesoporous cobalt oxide hollow spheres anode for high-rate and long-life lithium ion batteries, J. Phys. Chem. C 118 (2014) 2263e2272. [35] Z. Fu, Y. Wang, Y. Zhang, Q. Qin, Electrochemical reaction of nanocrystalline Co3O4 thin film with Lithium, Solid State Ion. 170 (2004) 105e109. [36] J. Yan, T. Wei, W. Qiao, B. Shao, Q. Zhao, L. Zhang, Z. Fan, Rapid microwaveassisted synthesis of graphene nanosheet/Co3O4 composite for supercapacitors, Electrochim. Acta 55 (2010) 6973e6978. [37] Z. Shang, M. Sun, S. Chang, X. Che, X. Cao, L. Wang, Y. Guo, W. Zhan, Y. Guo, G. Lu, Activity and stability of Co3O4-based catalysts for soot oxidation: the enhanced effect of Bi2O3 on activation and transfer of oxygen, Appl. Catal. B Environ. 209 (2017) 33e44.
[38] Q. Liao, N. Li, S. Jin, G. Yang, C. Wang, All-solid-state symmetric supercapacitor based on Co3O4 nanoparticles on vertically aligned graphene, J. Am. Chem. Soc. 5 (2015) 5310e5317. [39] M. Liao, Y. Liu, Z. Hu, Q. Yu, Novel morphologic Co3O4 of flower-like hierarchical microspheres as electrode material for electrochemical capacitors, J. Alloy. Comp. 562 (2013) 106e110. [40] Y. Zheng, Z. Li, J. Xu, T. Wang, X. Liu, X. Duan, Y. Ma, Y. Zhou, C. Pei, Multichanneled hierarchical porous carbon incorporated Co3O4 nanopillar arrays as 3D binder-free electrode for high performance supercapacitors, Nano Energy 20 (2016) 94e107. [41] Z. Hai, L. Gao, Q. Zhang, H. Xu, D. Cui, Z. Zhang, D. Tsoukalas, J. Tang, S. Yan, C. Xue, Facile synthesis of core-shell structured PANI-Co3O4 nanocomposites with superior electrochemical performance in supercapacitors, Appl. Surf. Sci. 361 (2016) 57e62. [42] Q. Rong, L. Long, X. Zhang, Y. Huang, H. Yu, Layered cobalt nickel silicate hollow spheres as a highly-stable supercapacitor, Mater. Appl. Energy 153 (2015) 63e69. [43] Y. Wang, W. Lai, N. Wang, Z. Jiang, X. Wang, P. Zou, Z. Lin, H. Fan, F. Kang, C.P. Wong, C. Yang, A reduced graphene oxide/mixed-valence manganese oxide composite electrode for tailorable and surface mountable supercapacitors with high capacitance and super-long life, Energy Environ. Sci. 10 (2017) 941e949. [44] J. Yan, L. Yang, M. Cui, X. Wang, K. Chee, V.C. Nguyen, V. Kumar, A. Sumboja, M. Wang, P.S. Lee, Aniline tetramer-graphene oxide composites for high performance supercapacitors, Adv. Energy Mater. 4 (2014) 1400781. [45] Y. Wu, T. Zhang, F. Zhang, Y. Wang, Y. Ma, Y. Huang, Y. Liu, Y. Chen, In situ synthesis of graphene/single-walled carbon nanotube hybrid material by arcdischarge and its application in supercapacitors, Nano Energy 1 (2012) 820e827. [46] T. Li, S. Li, B. Zhang, B. Wang, D. Nie, Z. Chen, Y. Yan, N. Wan, W. Zhang, Supercapacitor electrode with a homogeneously Co3O4-coated multiwalled carbon nanotube for a high capacitance, Nanoscale Res. Lett. 10 (2015) 1e7. [47] Z. Lin, X. Qiao, Coral-like Co3O4 decorated N-doped carbon particles as active materials for oxygen reduction reaction and supercapacitor, Sci. Rep. 8 (2018), 1802-1111. [48] J. Xu, L. Gao, J. Cao, W. Wang, Z. Chen, Preparation and electrochemical capacitance of cobalt oxide (Co3O4) nanotubes as supercapacitor material, Electrochim. Acta 56 (2010) 732e736. [49] W. Liu, D. Jiang, J. Xia, J. Qian, K. Wang, H. Li, Preparation of hierarchical mesoporous Co3O4 bundle using [Bmim] TA as a multi-role starting material and its supercapacitor application, Monatshefte Chem. 145 (2014) 19e22. [50] H. Wang, Y. Shi, Z. Li, W. Zhang, S. Yao, Synthesis and electrochemical performance of Co3O4/graphene, Chem. Res. Chin. Univ. 30 (2014) 650e655. [51] Y. Wang, Y. Lei, J. Li, L. Gu, H. Yuan, D. Xiao, Synthesis of 3D-nanonet hollow structured Co3O4 for high capacity supercapacitor, ACS Appl. Mater. Interfaces 6 (2014) 6739e6747. [52] Y.F. Li, Z.Y. Hai, X.J. Hou, H.Y. Xu, Z.X. Zhang, D.F. Cui, C.Y. Xue, B.Z. Zhang, Selfassembly of 3D fennel-like Co3O4 with thirty-six surfaces for high performance supercapacitor, J. Nanomater. (2017) 1404328. [53] G. Sun, L. Ma, J. Ran, X. Shen, H. Tong, Incorporation of homogeneous Co3O4 into a nitrogen-doped carbon aerogel via a facile in situ synthesis method: implications for high performance asymmetric supercapacitors, J. Mater. Chem. 4 (2016) 9542e9554. [54] X. Deng, J. Li, S. Zhu, F. He, C. He, E. Liu, C. Shi, Q. Li, N. Zhao, Metal-organic frameworks-derived honeycomb-like Co3O4/three-dimensional graphene networks/Ni foam hybrid as a binder-free electrode for supercapacitors, J. Alloy. Comp. 693 (2017) 16e24. [55] L. Xie, F. Su, L. Xie, X. Li, Z. Liu, Q. Kong, X. Guo, Y. Zhang, L. Wan, K. Li, C. Lv, C. Chen, Self-assembled 3D graphene-based aerogel with Co3O4 nanoparticles as high-performance asymmetric supercapacitor electrode, ChemSusChem 8 (2015) 2917e2926. [56] X. Lu, D. Wu, R. Li, Q. Li, S. Ye, Y. Tong, G. Li, Hierarchical NiCo2O4 nanosheets@ hollow microrod arrays for high-performance asymmetric supercapacitors, J. Mater. Chem. 2 (2014) 4706e4713. [57] W. Liu, H. Fan, W. Shen, S. Qu, Facile and sustainable synthesis of Co3O4@ hollow-carbon-fiber for a binder-free supercapacitor electrode, ChemistrySelect 1 (2016) 6469e6475. [58] T. Liu, L. Zhang, W. You, J. Yu, Core-shell nitrogen-doped carbon hollow spheres/Co3O4 nanosheets as advanced electrode for high-performance supercapacitor, Small 14 (2018) 1702407. [59] C. Wu, J. Cai, Q. Zhang, X. Zhou, Y. Zhu, P. Shen, K. Zhang, Hierarchical mesoporous zinc-nickel-cobalt ternary oxide nanowire arrays on nickel foam as high-performance electrodes for supercapacitors, ACS Appl. Mater. Interfaces 7 (2015) 26512e26521. [60] K. Xu, W. Li, Q. Liu, B. Li, X. Liu, L. An, Z. Chen, R. Zou, J. Hu, Hierarchical mesoporous NiCo2O4@MnO2 core-shell nanowire arrays on nickel foam for aqueous asymmetric supercapacitors, J. Mater. Chem. 2 (2014) 4795e4802. [61] C. Tang, X. Yin, H. Gong, Superior performance asymmetric supercapacitors based on a directly grown commercial mass 3D Co3O4@Ni(OH)2 core-shell electrode, ACS Appl. Mater. Interfaces 5 (2013) 10574e10582. [62] C. Zhang, L. Xie, W. Song, J. Wang, G. Sun, K. Li, Electrochemical performance of asymmetric supercapacitor based on Co3O4/AC materials, J. Electroanal. Chem. 706 (2013) 1e6.
Please cite this article as: H. Chen et al., Facile synthesis of 3D gem shape Co3O4 with mesoporous structure as electrode for high-performance supercapacitors, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.152939
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Facile synthesis of 3D gem shape Co3O4 with mesoporous structure as electrode for high-performance supercapacitors Hongmei Chen a, Chenyang Xue a, **, Zhenyin Hai b, c, Danfeng Cui a, Maoxing Liu d, e, Yuankai Li a, Wendong Zhang a, * a
Science and Technology on Electronic Test and Measurement Laboratory, North University of China, Taiyuan, Shanxi, 030051, China Center for Environmental & Energy Research, Ghent University Global Campus, Incheon 21985, South Korea Department of Solid State Sciences, Ghent University, Ghent, 9000, Belgium d Department of Mathematics, North University of China, Taiyuan, 030051, China e Department of Mathematics, Qingdao University of Science and Technology, Qingdao, 266061, China b c
a r t i c l e i n f o
a b s t r a c t
Article history: Received 23 July 2019 Received in revised form 28 October 2019 Accepted 6 November 2019 Available online xxx
In this work, a 3D gem shape Co3O4 nanomaterial using nickel foam (Ni foam) as substrate was synthesized as supercapacitor electrode. The morphology and structures of the Co3O4 were characterized by various test-methods including XRD, BET, FTIR, TG, SEM, TEM and XPS. The fabricated Co3O4 nanomaterial achieved an excellent capacitance of 1060.0 F g1 at 1 A g1 and a super-long cycling life with 99.6% retention rate after 5000 cycles at 8 A g1. Moreover, the as-fabricated Co3O4//AC supercapacitor, with the as-prepared Co3O4 as positive electrode and the activated carbon as negative electrode, delivered a high energy density (44.99 Wh kg1) at the power density of 0.2 kW kg1. The superior performances were mainly due to the high specific surface area, the suitable pore structure, and the uniformed 3D “gem shape” morphology of the Co3O4 nanomaterials. This work is of great significance to the development of high-performance energy storage devices and even to other application fields such as photocatalysis and sensors. © 2019 Elsevier B.V. All rights reserved.
Keywords: Co3O4 Gem shape Hydrothermal Supercapacitor
1. Introduction Our daily life depends heavily on electricity energy. At present, fossil fuel is the main energy source for human production and living. With the growth of global energy consumption, nonrenewable energy sources such as fossil fuels will be ultimately exhausted in the near future, which will have a serious impact on the environment [1]. Thus, the development of new types of clean and efficient energy storage technology has attracted more and more attentions in both academia and industry. Supercapacitors have led to extensive researches because they possess many advantages including high power density and low cost [2e4]. Recently, various transition-metal oxides were extensively explored and applied in the supercapacitors, such as NiO [5], NiCo2O4 [6,7], RuO2 [8], Co3O4 [9e11], MnO2 [12e14] and ZnO [15].
* Corresponding author. ** Corresponding author. E-mail addresses: [email protected] (C. Xue), [email protected] (W. Zhang).
Co3O4, as a transition metal oxide with spinel structure and a ptype semiconductor, has attracted great attentions in many fields such as supercapacitors [16], sensors [17] photocatalysis [18] due to the high theoretical capacitance (3560 F g1), low cost, natural abundance, and the appropriate band gap energy (2.1eV). In the application for supercapacitors, over the past decade, Co3O4 materials have attracted high research interests in obtaining excellent electrochemical performances. For example, Wang et al. [19] revealed that the crater-like Co3O4 delivered a capacitance of 102 F g1 and the capacitance can keep 74% after 500 cycles. Meng et al. [20] reported that the Co3O4 nanorods showed a specific capacity of 262 F g1 at 5 mV/s. The needle-like Co3O4 nanorods with the highest capacitance of 111 F g1 and 88.2% capacitance retention after 1000 cycles were reported [21]. Cao et al. [22] reported the Co3O4 hollow octahedra with a charge storage capacitance of 192 F g1. Although some progress on the Co3O4 electrode materials has been made, there are still some drawbacks, which limit their further practical application, such as low capacitance, low energy density, and poor cycle stability. Hence, it is urgent to fabricate the Co3O4 electrode with higher storage capacity and excellent cycling
https://doi.org/10.1016/j.jallcom.2019.152939 0925-8388/© 2019 Elsevier B.V. All rights reserved.
Please cite this article as: H. Chen et al., Facile synthesis of 3D gem shape Co3O4 with mesoporous structure as electrode for high-performance supercapacitors, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.152939
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stability. Compared to other materials preparation methods, the materials synthesized by hydrothermal method has the advantages of smaller particle size, more uniform size distribution, lighter particle agglomeration, and it is easy to get suitable stoichiometric and crystal shapes. In this work, 3D gem shape Co3O4 with mesoporous structure was synthesized via a hydrothermal process. The physical and chemical structural properties of the Co3O4 were measured. Meanwhile, the electrochemical performance for the Co3O4 nanomaterial was tested in 6.0 M KOH. The Co3O4 electrode showed a high mass capacitance of 1060.0 F g1 at 1 A g1. Besides, the capacitance retention can reach 99.6% after 5000 discharge-charge cycles at 8 A g1. Moreover, the two-electrode device (Co3O4//AC) was fabricated and tested. The highest energy density was 44.99 Wh kg1 at power density of 0.2 kW kg1. 2. Experimental 2.1. Material synthesis The chemical reagents in this paper are analytically pure and used without further purification. Synthesis of Co3O4: The Ni foam substrate was washed by acetone, hydrochloric acid, and deionized water for 15 min, respectively. Then the Ni foam was dried at 70 C. In a typical preparation process of Co3O4, 6 mmol Co(NO3)2$6H2O and 18 mL of deionized water were mixed under vigorous magnetic stirring for 10 min. Then, 12 mL ammonia solution was dropped and stirred for 30 min. Finally, the resulting solution with the Ni foam substrate was transferred into 50 mL stainless steel autoclave and kept for 10 h under 120 C. After the hydrothermal reaction, the obtained precursor was washed with deionized water, dried at 70 C for 5 h, and calcined at 300 C for 2 h at a heating rate of 2 C min1. The Co(OH)2 materials were preparation by sedimentary of (Co(NO)2$6H2O) as shown below: þ CoðNoÞ2 , 6H2 O þ 2NH4 OH / COðOHÞ2 þ 2NOþ 3 þ 2NH4
þ 6H2 O
(1)
The Co3O4 structure was formed by calcinating the as-prepared Co(OH)2 at 300 C shown as below: D,300 C
CoðOHÞ2 þ 1=2O2 !Co3 O4 þ 3H2 O
(2)
tests were all performed over an electrochemical workstation (RST 5000). The three-electrode test was performed with the Co3O4 on the Ni foam as the working electrode, a platinum wire as the auxiliary electrode, and a saturated calomel electrode as the reference electrode. Cyclic voltammetry (CV) test and galvanostatic charge-discharge measurements were carried out to evaluate the electrochemical properties. The mass capacitance was calculated with the following equation:
C¼
I Dt ms DV
(3)
where C is the mass specific capacitance (F g1), I (A) is the discharge current, Dt (s) is the discharge time, ms (g) is active material quality, and DV is the charge and discharge potential difference. The weight of active material was approximately 9.98 mg/ cm2. Moreover, the two-electrode device was fabricated with the Co3O4 as positive and AC as negative electrode. The negative electrode was prepared by mixing AC, acetylene black and PVDF in ethanol with a mass ratio of 8:1:1 using polytetrafluoroethylene (PTFE) as binder. The mass balance of the positive and negative electrodes can be expressed as the following equation [23e25]:
mþ C DV ¼ m Cþ DVþ
(4)
Among which, m, C, and DV stand for the weight of active materials, specific capacitance, and potential window for each electrode, respectively. The “þ” and “” represent the positive and negative electrodes. The weight of Co3O4 and carbon was around 9.98 and 13.2 mg according to the analysis results. The energy density and power density were obtained according to the following equations [26]:
C¼
I Dt mDV
(5)
E¼
C ðDVÞ2 2
(6)
P¼
E t
(7)
where E is the energy density (Wh kg1), P stands for the power density (kW kg1), and C, V, and t are mass capacitance (F g1), potential window (V) and discharge times (h), respectively.
2.2. Material characterizations 3. Results and discussion SEM and TEM measurement were performed with FEI Inspect F50 and FEI Inspect F30. The texture properties were measured by N2 adsorption-desorption isotherms on a NOVA2200e instrument using the pure Co3O4 sample separated from the Co3O4 on Ni foam. The chemical composition of the sample was determined with a D2 Phaser desktop/max-RAX-ray diffractometer (Bruker, Germany) ranging from 15 to 85 . FTIR spectra were recorded on a NEXUS Thermo Nicolet IR-spectrometer. The thermogravimetric test was performed on a PerkinElmer STA 800 instrument from 50 C to 600 C in the air atmosphere and the heating rate was 5 C/min. XPS was carried out on an ESCALAB 250Xi spectrometer. SEM and high HRTEM measurement were performed with FEI Inspect F50 and FEI Inspect F30. 2.3. Performance measurements The three-electrode configuration and the two-electrode system
3.1. Structure and morphology The XRD patterns of the Co3O4 and its precursor were tested to display the phase structure in Fig. 1. The series of diffraction peaks at 2q of 44.51, 51.84 , and 76.39 belonged to (111), (200), and (220) planes of Ni (JCPDS 04-0850). For the precursor, the diffraction peaks at 2q of 19.06 , 37.92 , 38.67 and 57.91 were assigned to the lattice planes of the Co(OH)2 species (JCPDS 30-0443). Moreover, the peaks centered at 2q ¼ 19.01, 36.87, 38.54 , 55.66 , 59.42 , 65.23 were assigned to the lattice planes of Co3O4 from the Co3O4 material (JCPDS 04-0850). The result suggested the successful preparation of Co(OH)2 after the hydrothermal process while the Co3O4 was formed after the calcination of the precursor. The FTIR spectra of the precursor Co(OH)2 and the Co3O4 are shown in Fig. 2a. For the precursor, the peak centered at 3624 cm1 matches well with the OeH stretching vibration of CoeOH group
Please cite this article as: H. Chen et al., Facile synthesis of 3D gem shape Co3O4 with mesoporous structure as electrode for high-performance supercapacitors, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.152939
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Fig. 1. XRD patterns of the precursor Co(OH)2 and the Co3O4.
while the peak at 1630 cm1 belongs to the bending vibration of the absorbed interlayer water molecule, and another peak at around 1386 cm1 is attributed to the n3 vibration of NO 3 , which indicates that nitrate ions may adsorb on the surface of the precursor [27e29]. Besides, the FTIR spectrum of the final Co3O4 is also shown in Fig. 2a, and the two strong peaks at 660 and 570 cm1 correspond to the stretching vibration of Co(2p)-O bond and Co(3p)-O bond, respectively [30e32]. To analyze the thermal behavior of the Co(OH)2 precursor, the thermogravimetric analysis was tested in the air atmosphere as presented in Fig. 2b. The thermogravimetric analysis curve indicated that the decomposition process began at about 170 C and the abrupt change process of the weight inferred the phase change from Co(OH)2 to the Co3O4 [33]. Additionally, about 11.2% weight percentage loss happened in the temperature-programmed process from 50 C to 600 C, which was close to the theoretical value of 13.6%. As presented in Fig. 3a-b, the Ni foam is almost entirely and uniformly covered by the 3D “gem shape” particles. Furthermore, the Co3O4 sample was analyzed by TEM. As displayed in Fig. 3d, the lattice constants of 0.205 and 0.214 nm are corresponded to the dspacing of (311) and (222) respectively, and the results are in line
3
with the XRD results. Meanwhile, the energy dispersive spectrometer mapping (EDS) of the Co3O4 was test to analyze the distribution of Co and O (Fig. 3e) and the results revealed that the Co and O elements were successfully scattered on the Ni foam substrate. The N2-adsorption was carried out to explore the pore structure and the surface area. Fig. 4a showed the N2 adsorption-desorption of the Co3O4 nanomaterial and the isotherm was attributed to type-IV. More importantly, the Co3O4 nanomaterial had a large specific surface area of 117.7 m2 g1. Additionally, the pore size distribution of Co3O4 particle was presented in Fig. 4b. The pore size was distributed under 20 nm. Specifically, the pore size and the pore volume were analyzed to be 13.6 nm and 0.069 cc g1 respectively, indicating that the Co3O4 belonged to the mesoporous material. It is well known that the sample morphologies vary greatly due to the different preparation procedures, further leading to diversity in the structure properties including the specific surface area. Due to the unique 3D “gem shape” mesoporous structure of the prepared oxide, a higher surface area of the sample was obtained compared to the other similar materials, such as Co3O4 nanocubes (74.8 m2 g1) [2], Co3O4 crater-like microspheres (60 m2 g1) [19], Co3O4 nanorods (23 m2 g1) [20], 2D Co3O4 nanosheet (27.15 m g1) [26], and even some composite oxides including NiCo2O4 (48.61 m2 g1), NiCo2O4@MnMoO4 (65.25 m2 g1) [6], NiCo2O4 with diamond-shaped hexahedron structure (59.882 m2 g1) [7], ZnOeCo3O4 (53.66 m2 g1) [24], and NiCo2O4@Co3O4 (73.43 m2 g1) [26]. Generally speaking, a high specific area means more electrochemically active sites, which can promote the redox reaction to obtain better electrochemical performance. Hence, the high specific surface area and the suitable pore structure are important factors for the perfect electrochemical performance of the Co3O4 nanomaterial. XPS presented in Fig. 5 were tested in order to identify the surface element composition of the Co3O4. As shown in Fig. 5a, there are two peaks centered at about 795.1 eV and 780.1 eV, which were assigned to the metallic peaks of Co 2p1/2 and Co 2p3/2, respectively [34e36]. Besides, only one peak could be seen from Fig. 5b and the peak located at 530.1 eV was assigned to O1s [37], which conforms with the lattice oxygen in the Co3O4 phase. 3.2. Electrochemical test The cyclic voltammetry (CV) measurements were performed to explore the electrochemical properties of the Co3O4. Fig. 6a shows CV curves of the Co3O4 at different scan rates from 5 to 100 mV/s in the voltage window ranging from 0 to 0.6 V. There are obvious
Fig. 2. (a) FTIR spectra of the Co3O4 and Co(OH)2, and (b) the thermogravimetric analysis curve of the Co(OH)2 sample.
Please cite this article as: H. Chen et al., Facile synthesis of 3D gem shape Co3O4 with mesoporous structure as electrode for high-performance supercapacitors, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.152939
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Fig. 3. (aeb) SEM images, (ced) TEM images and (e) EDS mapping of the Co3O4.
Fig. 4. (a)N2 adsorption-desorption isotherm and (b) the corresponding pore size distribution of Co3O4 particles.
redox peaks on the CV curve of Co3O4 and the results inferred that the capacitance of Co3O4 derives from pseudocapacitance [38,39]. The redox peak in the cyclic voltammetry curve gradually weakened in the three-electrode system with the increase of scanning speed due to the internal resistance of the electrode material itself and between the solution and the electrode. The corresponding oxidation and reduction peaks move to the poles respectively and this phenomenon was due to the polarization effect. With the increase of scanning speed, the cyclic voltammetry curve maintains a good shape, indicating that the Co3O4 material has a good power performance. The faradaic reactions can be described by the following formulas [40,41]: Co3O4 þ OH þ H2O ¼ 3CoOOH þ e
(8)
CoOOH þ OH ¼ 3CoOOH þ H2O þ e
(9)
Fig. 6b shows the galvanostatic discharge results of the Co3O4 at different current densities and the variation trend of mass specific capacitance with current density increasing is shown in Fig. 6c. As presented in Fig. 6c, the mass capacitances of the Co3O4 electrode are 1060.0, 999.7, 947.3, 902.0, 851.3, 720 and 642.5 F g1 at different current densities of 1, 2, 3, 4, 5, 8 and 10 A g1, respectively. The mass capacitances decreased as the current densities increased, and the mass capacitance at 10 A g1 was still 60.6% of that of the capacitance at 1 A g1. The mass capacitance decreasing was mainly because the existence of internal active sites couldn’t completely maintain the redox transition in the case of fast scanning speed [42]. The mass capacitance of the Co3O4 material is much higher than that of the other supercapacitors reported (Table 1). Furthermore, the galvanostatic cycling experiment was performed to investigate the cycling stability of the Co3O4 electrode at a current density of 8 A g1 and the result was shown in Fig. 6d. The Co3O4
Please cite this article as: H. Chen et al., Facile synthesis of 3D gem shape Co3O4 with mesoporous structure as electrode for high-performance supercapacitors, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.152939
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Fig. 5. XPS of (a) Co 2p and (b) O 1s of the Co3O4.
Fig. 6. (a)The CV curves, (b) galvanostatic charge-discharge curves, (c) specific capacitances at different current density, and (d) cycling stability of the composite at the current density of 8 A g1 of the Co3O4.
electrode exhibited good stability with cycling efficiency of 99.6% after 5000 cycles. The fluctuations of capacity retention rate during long cycling experiment may be caused by the temperature variation due to the day and night alternation [43e45]. The electrochemical impedance spectroscopy (EIS) was performed with a frequency range from 0.1 Hz to 10 kHz for the Co3O4 electrode material and Fig. 7a showed Nyquist plots of the Co3O4 electrode along with its fitted curve. Simultaneously, an equivalent circuit was also used to obtain the charge-transfer resistance (Fig. 7b). As seen in Fig. 7a, the Nyquist curve is an arc at high
frequencies and an oblique straight line at low frequencies. The radius of the arc in the high frequency region represents the charge transfer resistance (Rct) and the small arc radius reveals that the resistance of the Co3O4 material is very small. The low-frequency part in the Nyquist curve stands for the Warburg impedance and it was determined by the slope of the line. In the EIS, Rs, C, Rct, Zw stand for the electrolyte resistance, capacitance, charge transfer resistance, Warburg impedance, respectively. Also, Fig. 7a displayed that the fitting curves matched with the EIS curves perfectly and the fitting error was only 1.79 1005 of Co3O4 electrode.
Please cite this article as: H. Chen et al., Facile synthesis of 3D gem shape Co3O4 with mesoporous structure as electrode for high-performance supercapacitors, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.152939
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Table 1 Different electrochemical properties in previous reports for supercapacitors Material
Specific Capacitance (F g1)
current density (A g1)
Capacity Retention//Cycling number
Reference
Co3O4 CWs-Co3O4 Co3O4-0.5/MWCNT Co3O4/N-CP Co3O4 Co3O4 Co3O4/Graphene Co3O4 Co3O4 Co3O4
814 978.9 273 316.2 574 390.4 357 739 384.375 1060
1 0.5 0.5 1 0.1 1 0.5 1 3 1
e 94.6%//2000 88%//500 93%//20000 95%//1000 95%//500 87%//1000 90.2%//1000 96.54%//1000 99.6%//5000
[24] [40] [46] [47] [48] [49] [50] [51] [52] This work
Fig. 7. (a) The Nyquist plots and the fitted plots, and (b) the equivalent circuit diagram of Co3O4 electrode.
Moreover, the Rs, Rct1, Rct2, Zw of the Co3O4 electrode are 0.35 U, 0.85 U, 0.12 U and 1.499, respectively. To further study the practical application of supercapacitor, the Co3O4//AC supercapacitor was assembled and the two-electrode performance was measured using Co3O4 as positive electrode material and AC as negative electrode material. Firstly, the CV curves were investigated to contrast the capacitive performance of Co3O4 and AC electrodes, and the Co3O4 electrode had a higher capacitance (Fig. 8a). Furthermore, the CV and galvanostatic chargedischarge tests for the Co3O4//AC two-electrode system were also measured. From Fig. 8b it can be seen that the CV curve shows an obvious redox peak, indicating that the two-electrode system undergoes redox reaction as the scan rate increases from 30 to 300 mV s1. Additionally, Fig. 8c indicated that the mass capacitances of the Co3O4 electrode were 253.1, 236.7, 167.7, 161.6 and 131.3 F g1 at different current densities of 0.5, 1, 2, 3 and 5 A g1, respectively. Fig. 8d displayed the relationship between specific capacitance and current density. As we can see, the specific capacitance decreased with the current increasing for the similar reason as the performance in the three-electrode system that the faster the scanning rate, the less the redox transition can be maintained by the presence of internal active sites [42]. Furthermore, Fig. 9 showed the energy density and power density of the Co3O4//AC and other reported works. The energy density of Co3O4//AC showed the maximum of 44.99 Wh kg1 at the power density of 0.2 kW kg1, and the energy density still maintained 23.33 Wh kg1 even at the high power density of 2 kW kg1. Moreover, comparisons had been made between our work and other previous works, such as nitrogen-doped carbon aerogel/cobalt oxide (NCA/Co3O4, 33.43 Wh kg1 at the power density of 0.375 kW kg1) [53], Co3O4/three-dimensional graphene
networks/Ni foam (Co3O4/3DGN/NF, 7.5 Wh kg1 at the power density of 0.794 kW kg1) [54], 3D Co3O4-RGO (40.65 Wh kg1 at the power density of 0.34 kW kg1) [55], NiCo2O4@hollow microrod arrays (15.42 Wh/kg at the power density of 0.5 kW kg1) [56], Co3O4/Hollow-Carbon-Fiber (24.31 Wh kg1 at the power density of 0.75 kW kg1) [57], Co3O4/nitrogen-doped carbon hollow sphere (34.5 Wh kg1 at the power density of 0.735 kW kg1) [58], ZneNieCo ternary oxide (35.6 Wh kg1 at the power density of 0.1876 kW kg1) [59], NiCo2O4@MnO2 (35 Wh kg1 at the power density of 0.163 kW kg1) [60], 3D Co3O4@Ni(OH)2 (41.9 Wh kg1 at the power density of 0.0361 kW kg1) [61], Co3O4/AC (24.9 Wh kg1 at the power density of 0.225 kW kg1) [62]. It can be concluded that the results of the energy density and the power density in this work were superior to many other Co3O4 samples and even some composite oxides, suggesting the tremendous application potential of the Co3O4 electrode material. 4. Conclusions In conclusion, the 3D Co3O4 gem shape electrode material with mesoporous structure has been fabricated by a simple hydrothermal method and the corresponding electrochemical properties were tested. The Co3O4 delivered a high mass capacity of 1060.6 F g1 at 1 A g1. Besides, the Co3O4 showed a perfect mass capacity of 717.1 F g1 after 5000 cycles test at 8 A g1, which was about 99.6% of its initial capacitance. Moreover, its maximum energy density was obtained to be 44.99 Wh kg1. Hence, the Co3O4 preparation via our new synthetic route displayed excellent mass capacity and energy density, along with perfect cycling stability. Meanwhile, the prepared Co3O4 material owned obvious crystal structure, excellent crystallinity, high specific surface area and
Please cite this article as: H. Chen et al., Facile synthesis of 3D gem shape Co3O4 with mesoporous structure as electrode for high-performance supercapacitors, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.152939
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Fig. 8. The electrochemical performance of the supercapacitor of Co3O4//AC: (a) CV curves of Co3O4 electrode and AC electrode; (b) CV curves and (c) galvanostatic charge-discharge curves of Co3O4//AC; (d) the specific capacitance at different current density.
Acknowledgments Financial support from the School Foundation for North University of China (Grant No. 110246), Shanxi Science foundation of China(Grant No. 201801D221197), Shanxi Scholarship Council of China (Grant No. 2017-094), Shanxi Scholarship Council of China (Grant No. 2017-094), the National Science Foundation of China (Grant No.61501408), and Shanxi ‘1311 project’ Key Subject Construction(1331KSC) for supporting this work. References
Fig. 9. The energy density and power density of Co3O4//AC and other reported works.
suitable pore structure. Therefore, the Co3O4 material proposed in this work has a good application prospect in the electrode of supercapacitor and it may be a potential candidate in many other research fields such as photocatalysis and sensors.
Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
[1] N. Zhao, L. Kong, Y. Dong, G. Wang, X. Wu, P. Jiang, Insight into the crucial factors for photochemical deposition of cobalt cocatalysts on g-C3N4 photocatalysts, ACS Appl. Mater. Interfaces 10 (2018) 9522e9531. [2] M. Pal, R. Rakshit, A.K. Singh, K. Mandal, Ultra high supercapacitance of ultra small Co3O4 nanocubes, Energy 103 (2016) 481e486. [3] S. Park, S. Kim, Effect of carbon blacks filler addition on electrochemical behaviors of Co3O4/graphene nanosheets as a supercapacitor electrodes, Electrochim. Acta 89 (2013) 516e522. [4] G. Wang, L. Zhang, J. Zhang, A review of electrode materials for electrochemical supercapacitors, Chem. Soc. Rev. 41 (2012) 797e828. [5] M. Liu, J. Chang, J. Sun, L. Gao, Synthesis of porous NiO using NaBH4 dissolved in ethylene glycol as precipitant for high-performance supercapacitor, Electrochim. Acta 107 (2013) 9e15. [6] Y. Chen, Y. Li, Z. Hai, Y. Li, S. Kan, J. Chen, X. Chen, S. Zhuiykov, D. Cui, C. Xue, Facile-synthesized NiCo2O4@MnMoO4 with novel and functional structure for superior performance supercapacitors, Appl. Surf. Sci. 452 (2018) 413e422. [7] Y. Li, X. Hou, Z. Zhang, Z. Hai, H. Xu, D. Cui, S. Zhuiykov, C. Xue, NiCo2O4 particles with diamond-shaped hexahedron structure for high-performance supercapacitors, Appl. Surf. Sci. 436 (2018) 242e251. [8] C. Hu, K. Chang, M. Lin, Y. Wu, Design and tailoring of the nanotubular arrayed architecture of hydrous RuO2 for next generation supercapacitors, Nano Lett. 6 (2006) 2690e2695. [9] V. Srinivasan, J.W. Weidner, Capacitance studies of cobalt oxide films formed via electrochemical precipitation, J. Power Sources 108 (2002) 15e20. [10] W. Du, R. Liu, Y. Jiang, Q. Lu, Y. Fan, F. Gao, Facile synthesis of hollow Co3O4 boxes for high capacity supercapacitor, J. Power Sources 227 (2013) 101e105.
Please cite this article as: H. Chen et al., Facile synthesis of 3D gem shape Co3O4 with mesoporous structure as electrode for high-performance supercapacitors, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.152939
8
H. Chen et al. / Journal of Alloys and Compounds xxx (xxxx) xxx
[11] X. Feng, C. Shen, Y. Yu, S. Wei, C. Chen, Synthesis and electrochemical properties of sticktight-like and nanosheet Co3O4 particles, J. Power Sources 230 (2013) 59e65. [12] Z. Huang, Y. Song, D. Feng, Z. Sun, X. Sun, X. Liu, High mass loading MnO2 with hierarchical nanostructures for supercapacitors, ACS Nano 12 (2018) 3557e3567. [13] H. Jia, Y. Cai, X. Zheng, J. Lin, H. Liang, J. Qi, J. Cao, J. Feng, W. Fei, Mesostructured carbon nanotube-on-MnO2 nanosheet composite for highperformance supercapacitors, ACS Appl. Mater. Interfaces 10 (2018) 38963e38969. [14] J. Kang, A. Hirata, L. Kang, X. Zhang, Y. Hou, L. Chen, C. Li, T. Fujita, K. Akagi, M. Chen, Enhanced supercapacitor performance of MnO2 by atomic doping, Angew. Chem. Int. Ed. 52 (2013) 1664e1667. [15] J. Yuan, X. Zhang, C. Chen, Y. Hao, R. Agrawal, C. Wang, W. Li, H. Yu, Y. Yu, X. Zhu, Z. Xiong, Y. Xie, Facile fabrication of three-dimensional porous ZnO thin films on Ni foams for lithium ion battery anodes, Mater. Lett. 190 (2017) 37e39. [16] T. Akamatsu, T. Itoh, N. Izu, W. Shin, Effect of noble metal addition on Co3O4based gas sensors for selective NO detection, Sens. Mater. 28 (2016) 1191e1201. [17] H. Xu, C. Xia, S. Wang, F. Han, M. Karbalaeiakbari, Z. Hai, S. Zhuiykov, Electrochemical non-enzymatic glucose sensor based on hierarchical 3D Co3O4/Ni heterostructure electrode for pushing sensitivity boundary to a new limit, Sens. Actuator B Chem. 267 (2018) 93e103. [18] Q. Zhang, Z. Hai, A. Jian, H. Xu, C. Xue, S. Sang, Synthesis of p-Co3O4/n-TiO2 nanoparticles for overall water splitting under visible light irradiation, Nanomaterials 6 (2016) 138e148. [19] L. Wang, X. Liu, X. Wang, X. Yang, L. Lu, Preparation and electrochemical properties of mesoporous Co3O4 crater-like microspheres as supercapacitor electrode materials, Curr. Appl. Phys. 10 (2010) 1422e1426. [20] T. Meng, Q. Xu, Z. Wang, Y. Li, Z. Gao, X. Xing, T. Ren, Co3O4 Nanorods with self-assembled nanoparticles in queue for supercapacitor, Electrochim. Acta 180 (2015) 104e111. [21] T. Zhu, J. Chen, X. Lou, Shape-controlled synthesis of porous Co3O4 nanostructures for application in supercapacitors, J. Mater. Chem. 20 (2010) 7015e7020. [22] Y. Cao, F. Yuan, M. Yao, J. Bang, J. Lee, A new synthetic route to hollow Co3O4 octahedra for supercapacitor applications, CrystEngComm 16 (2014) 826e833. [23] T. Wang, S. Zhang, X. Yan, M. Lyu, L. Wang, J. Bell, H. Wang, 2methylimidazole-derived Ni-Co layered double hydroxide nanosheets as high rate capability and high energy density storage material in hybrid supercapacitors, ACS Appl. Mater. Interfaces 9 (2017) 15510e15524. [24] M. Gao, W. Wang, Q. Rong, J. Jiang, Y. Zhang, H. Yu, Porous ZnO-coated Co3O4 nanorod as a high-energy-density supercapacitor material, ACS Appl. Mater. Interfaces 10 (2018) 23163e23173. [25] X. Li, Y. Liu, Z. Jin, P. Li, X. Chen, D. Xiao, Enhanced electrochemical performance of C-NiO/NiCo2O4//AC asymmetric supercapacitor based on material design and device exploration, Electrochim. Acta 296 (2019) 335e344. [26] P. Sennu, V. Aravindan, Y.-S. Lee, High energy asymmetric supercapacitor with 1D@2D structured NiCo2O4@Co3O4 and jackfruit derived high surface area porous carbon, J. Power Sources 306 (2016) 248e257. [27] A.-A.M. Barmi, M. Aghazadeh, B. Arhami, H.M. Shiri, A.A. Fazl, E. Jangju, Porous cobalt hydroxide nanosheets with excellent supercapacitive behavior, Chem. Phys. Lett. 541 (2012) 65e69. [28] D. Ghosh, S. Giri, C.K. Das, Preparation of CTAB-assisted hexagonal platelet Co(OH)2/graphene hybrid composite as efficient supercapacitor electrode material, ACS Sustain. Chem. Eng. 1 (2013) 1135e1142. [29] Y. Li, Y. Wu, Critical role of screw dislocation in the growth of Co(OH)2 nanowires as intermediates for Co3O4 nanowire growth, Chem. Mater. 22 (2010) 5537e5542. [30] X. Tong, Z. Hai, D. Cui, L. Gao, Q. Zhang, H. Xu, Y. Ma, C. Xue, J. Liu, Investigation of lattice distortion of Co3O4 nanoparticles prepared by a carbon-assisted method, Microelectron. Eng. 159 (2016) 17e20. [31] Y. Wang, J. Shi, J. Cao, G. Sun, Z. Zhang, Synthesis of Co3O4 nanoparticles via the CTAB-assisted method, Mater. Lett. 65 (2011) 222e224. [32] S. Dubey, J. Kumar, A. Kumar, Y.C. Sharma, Facile and green synthesis of highly dispersed cobalt oxide (Co3O4) nanopowder: characterization and screening of its eco-toxicity, Adv. Powder Technol. 29 (2018) 2583e2590. [33] B. Wang, X. Lu, Y. Tang, Synthesis of snowflake-shaped Co3O4 with a high aspect ratio as a high capacity anode material for lithium ion batteries, J. Mater. Chem. 3 (2015) 9689e9699. [34] H. Sun, X. Sun, T. Hu, M. Yu, F. Lu, J. Lian, Graphene-wrapped mesoporous cobalt oxide hollow spheres anode for high-rate and long-life lithium ion batteries, J. Phys. Chem. C 118 (2014) 2263e2272. [35] Z. Fu, Y. Wang, Y. Zhang, Q. Qin, Electrochemical reaction of nanocrystalline Co3O4 thin film with Lithium, Solid State Ion. 170 (2004) 105e109. [36] J. Yan, T. Wei, W. Qiao, B. Shao, Q. Zhao, L. Zhang, Z. Fan, Rapid microwaveassisted synthesis of graphene nanosheet/Co3O4 composite for supercapacitors, Electrochim. Acta 55 (2010) 6973e6978. [37] Z. Shang, M. Sun, S. Chang, X. Che, X. Cao, L. Wang, Y. Guo, W. Zhan, Y. Guo, G. Lu, Activity and stability of Co3O4-based catalysts for soot oxidation: the enhanced effect of Bi2O3 on activation and transfer of oxygen, Appl. Catal. B Environ. 209 (2017) 33e44.
[38] Q. Liao, N. Li, S. Jin, G. Yang, C. Wang, All-solid-state symmetric supercapacitor based on Co3O4 nanoparticles on vertically aligned graphene, J. Am. Chem. Soc. 5 (2015) 5310e5317. [39] M. Liao, Y. Liu, Z. Hu, Q. Yu, Novel morphologic Co3O4 of flower-like hierarchical microspheres as electrode material for electrochemical capacitors, J. Alloy. Comp. 562 (2013) 106e110. [40] Y. Zheng, Z. Li, J. Xu, T. Wang, X. Liu, X. Duan, Y. Ma, Y. Zhou, C. Pei, Multichanneled hierarchical porous carbon incorporated Co3O4 nanopillar arrays as 3D binder-free electrode for high performance supercapacitors, Nano Energy 20 (2016) 94e107. [41] Z. Hai, L. Gao, Q. Zhang, H. Xu, D. Cui, Z. Zhang, D. Tsoukalas, J. Tang, S. Yan, C. Xue, Facile synthesis of core-shell structured PANI-Co3O4 nanocomposites with superior electrochemical performance in supercapacitors, Appl. Surf. Sci. 361 (2016) 57e62. [42] Q. Rong, L. Long, X. Zhang, Y. Huang, H. Yu, Layered cobalt nickel silicate hollow spheres as a highly-stable supercapacitor, Mater. Appl. Energy 153 (2015) 63e69. [43] Y. Wang, W. Lai, N. Wang, Z. Jiang, X. Wang, P. Zou, Z. Lin, H. Fan, F. Kang, C.P. Wong, C. Yang, A reduced graphene oxide/mixed-valence manganese oxide composite electrode for tailorable and surface mountable supercapacitors with high capacitance and super-long life, Energy Environ. Sci. 10 (2017) 941e949. [44] J. Yan, L. Yang, M. Cui, X. Wang, K. Chee, V.C. Nguyen, V. Kumar, A. Sumboja, M. Wang, P.S. Lee, Aniline tetramer-graphene oxide composites for high performance supercapacitors, Adv. Energy Mater. 4 (2014) 1400781. [45] Y. Wu, T. Zhang, F. Zhang, Y. Wang, Y. Ma, Y. Huang, Y. Liu, Y. Chen, In situ synthesis of graphene/single-walled carbon nanotube hybrid material by arcdischarge and its application in supercapacitors, Nano Energy 1 (2012) 820e827. [46] T. Li, S. Li, B. Zhang, B. Wang, D. Nie, Z. Chen, Y. Yan, N. Wan, W. Zhang, Supercapacitor electrode with a homogeneously Co3O4-coated multiwalled carbon nanotube for a high capacitance, Nanoscale Res. Lett. 10 (2015) 1e7. [47] Z. Lin, X. Qiao, Coral-like Co3O4 decorated N-doped carbon particles as active materials for oxygen reduction reaction and supercapacitor, Sci. Rep. 8 (2018), 1802-1111. [48] J. Xu, L. Gao, J. Cao, W. Wang, Z. Chen, Preparation and electrochemical capacitance of cobalt oxide (Co3O4) nanotubes as supercapacitor material, Electrochim. Acta 56 (2010) 732e736. [49] W. Liu, D. Jiang, J. Xia, J. Qian, K. Wang, H. Li, Preparation of hierarchical mesoporous Co3O4 bundle using [Bmim] TA as a multi-role starting material and its supercapacitor application, Monatshefte Chem. 145 (2014) 19e22. [50] H. Wang, Y. Shi, Z. Li, W. Zhang, S. Yao, Synthesis and electrochemical performance of Co3O4/graphene, Chem. Res. Chin. Univ. 30 (2014) 650e655. [51] Y. Wang, Y. Lei, J. Li, L. Gu, H. Yuan, D. Xiao, Synthesis of 3D-nanonet hollow structured Co3O4 for high capacity supercapacitor, ACS Appl. Mater. Interfaces 6 (2014) 6739e6747. [52] Y.F. Li, Z.Y. Hai, X.J. Hou, H.Y. Xu, Z.X. Zhang, D.F. Cui, C.Y. Xue, B.Z. Zhang, Selfassembly of 3D fennel-like Co3O4 with thirty-six surfaces for high performance supercapacitor, J. Nanomater. (2017) 1404328. [53] G. Sun, L. Ma, J. Ran, X. Shen, H. Tong, Incorporation of homogeneous Co3O4 into a nitrogen-doped carbon aerogel via a facile in situ synthesis method: implications for high performance asymmetric supercapacitors, J. Mater. Chem. 4 (2016) 9542e9554. [54] X. Deng, J. Li, S. Zhu, F. He, C. He, E. Liu, C. Shi, Q. Li, N. Zhao, Metal-organic frameworks-derived honeycomb-like Co3O4/three-dimensional graphene networks/Ni foam hybrid as a binder-free electrode for supercapacitors, J. Alloy. Comp. 693 (2017) 16e24. [55] L. Xie, F. Su, L. Xie, X. Li, Z. Liu, Q. Kong, X. Guo, Y. Zhang, L. Wan, K. Li, C. Lv, C. Chen, Self-assembled 3D graphene-based aerogel with Co3O4 nanoparticles as high-performance asymmetric supercapacitor electrode, ChemSusChem 8 (2015) 2917e2926. [56] X. Lu, D. Wu, R. Li, Q. Li, S. Ye, Y. Tong, G. Li, Hierarchical NiCo2O4 nanosheets@ hollow microrod arrays for high-performance asymmetric supercapacitors, J. Mater. Chem. 2 (2014) 4706e4713. [57] W. Liu, H. Fan, W. Shen, S. Qu, Facile and sustainable synthesis of Co3O4@ hollow-carbon-fiber for a binder-free supercapacitor electrode, ChemistrySelect 1 (2016) 6469e6475. [58] T. Liu, L. Zhang, W. You, J. Yu, Core-shell nitrogen-doped carbon hollow spheres/Co3O4 nanosheets as advanced electrode for high-performance supercapacitor, Small 14 (2018) 1702407. [59] C. Wu, J. Cai, Q. Zhang, X. Zhou, Y. Zhu, P. Shen, K. Zhang, Hierarchical mesoporous zinc-nickel-cobalt ternary oxide nanowire arrays on nickel foam as high-performance electrodes for supercapacitors, ACS Appl. Mater. Interfaces 7 (2015) 26512e26521. [60] K. Xu, W. Li, Q. Liu, B. Li, X. Liu, L. An, Z. Chen, R. Zou, J. Hu, Hierarchical mesoporous NiCo2O4@MnO2 core-shell nanowire arrays on nickel foam for aqueous asymmetric supercapacitors, J. Mater. Chem. 2 (2014) 4795e4802. [61] C. Tang, X. Yin, H. Gong, Superior performance asymmetric supercapacitors based on a directly grown commercial mass 3D Co3O4@Ni(OH)2 core-shell electrode, ACS Appl. Mater. Interfaces 5 (2013) 10574e10582. [62] C. Zhang, L. Xie, W. Song, J. Wang, G. Sun, K. Li, Electrochemical performance of asymmetric supercapacitor based on Co3O4/AC materials, J. Electroanal. Chem. 706 (2013) 1e6.
Please cite this article as: H. Chen et al., Facile synthesis of 3D gem shape Co3O4 with mesoporous structure as electrode for high-performance supercapacitors, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.152939