Preparation and electrochemical properties of CPAC/Mn3O4 nanocomposite electrode
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Novel nanocomposite electrode, coke powder activated carbon/Mn3O4 (CPAC/Mn3O4), was prepared by Sol–Gel method using CPAC/Mn(OH)2 as a precursor. The CPAC/Mn3O4 was characterized by field emission scanning electron microscopy and X-ray diffraction (XRD). The results show that the composite electrode material has a nano-rod structure and Mn3O4 is in mixed phase composed of MnO and MnO2. The influence factors on the electrochemical performance of electrode materials including manganese content of the precursor, different calcining temperature and time of the precursor were investigated. The results obtained from electrochemical measurement show that the electrode possesses better electrochemical performance with a manganese content of 20 wt % in precursor. In addition, the specific capacitance of CPAC/Mn3O4 nanocomposite electrode material could reach up to 277 F g−1 at a calcining temperature of 500 °C and a calcining time of 3 h, respectively.
KeywordsMn3O4 Specific Capacitance Electrode Material Calcine Temperature Manganese Oxide
Supercapacitor has been considered as a new extremely valuable energy storage device, because of its excellent functions such as fast charging and discharging, high power, fairly high energy density, long cycle life, and friendly to environment [1, 2, 3]. Manganese oxide as supercapacitor electrode material is relatively inexpensive and innocuous to environment, which has great potentials as a kind of alternative electrode material in supercapacitor systems [4, 5, 6, 7, 8]. Manganese oxides present complex crystal structure of manganese oxides, for instance, the MnO2 includes types of α, β, γ, δ, ε and ρ. The crystal structure of ε, ρ, γ are similar to each other, δ belongs to the layer structure, and others belong to the chain structure. Owing to different crystal structure of manganese oxide, they often exhibit different electrochemical properties, among which γ-MnO2 shows a relatively high electrochemical active property [9, 10]. So far, reports of manganese oxide used as electrode materials are mainly focused on γ-MnO2 and α-MnO2 [11, 12, 13, 14]. However, Mn3O4 used as electrode materials has rarely been reported.
Coke powder has been commonly known as the scrap material when the coke was produced in the process of the smashed in metallurgy, chemical industry, calcium carbide and other industries. Until now, the coke powder prepared by alkali activation has mainly been used in the wastewater treatment but seldom involved in electrode materials . In this work, coke powder activated carbon and CPAC/Mn3O4 composite electrode material were prepared in a continuation of our pervious study . The electrochemical performance of CPAC/Mn3O4 electrode materials, which was prepared under the conditions of different calcining temperature and time, were systematically investigated. Then the best preparation conditions were optimized.
2 Experimental method
2.1 Preparation of CPAC/Mn(OH)2
Coke powder activated carbons (CPACs) were prepared according to previous study . A certain quality of MnCl2·4H2O was dissolved in 50 mL water, magnetic stirring with 30 min, then according to 5,10, 20, 30,50 wt% of the amount of manganese added into CPAC, respectively, adding a few ethanol and stirring with 30 min. After that 10 wt% NH3·H2O was added by 6–8 drops per second,nearly for the pH = 10, and stirring with 6 h. Then standly aging for 4 h, depressurize filtering them, the products were fully rinsed to neutral and dried at 80 °C for 24 h.
2.2 Preparation of CPAC/Mn3O4
The prepared composite electrode materials was performed under the protection of N2, and calcined at different temperature (300, 400, 500 and 600 °C) for 2, 3, and 4 h respectively. After cooling down to room temperature, the sample was fully grinded in an agate mortar, and then put into the dryers.
2.3 Preparation of CPAC/Mn3O4 working electrodes
The working electrodes were prepared for electrochemical measurement. CPAC/Mn3O4 (80 wt%) was mixed with 10 wt% of acetylene black (>99.9 %) and 10 wt% of conducting graphite in an agate mortar and grinded equably. Then 5 wt% of polytetra-fluoroethylene (PTFE) aqueous suspension and a few drops of anhydrous ethanol were added into the CPAC/Mn3O4 mixture. After removing the solvent by evaporation, the resulting paste was pressed into the nickel foam substrate using a spatula with a coating area of about 10 mm × 10 mm, and dried in vacuum at 80 °C for 2 h, then the electrode of nickel foam was pressed at 10 MPa for 1–2 min, and dried in vacuum for 4 h.
2.4 Characterization and electrochemical measurement
The morphology of the electrodes was characterized by FESEM (JSM-6701F, Japan) and the structure was affirmed by XRD (RINT-2000, Japan). The electrochemical measurement of CPAC/Mn3O4 electrodes was carried out using an electrochemical working station (CHI660B, Shanghai, China) in a three electrode cell at room temperature. A platinum gauze electrode and a saturated calomel electrode (SCE) served as the counter electrode and the reference electrode, respectively. KOH solution (2 mol L−1) was used as the electrolyte, each electrode possessed about 8 mg of electro active material and had a geometric surface area of about 1 cm2. The charge and discharge properties of electrode materials, circulation current–voltage performance were measured.
3 Results and discussion
3.1 FESEM analysis
3.3 Charge/discharge test of CPAC/Mn(OH)2
In the above equation, C is the specific capacitance; I is the constant discharging current; Δt is the time period for the potential change ΔE; and m is the mass of the electrode materials measured.
3.4 The electrochemical characterizations of CPAC/Mn3O4
3.4.2 Cyclic voltammetry
Employing CPAC as a matrix, the precursor CPAC/Mn(OH)2 were prepared by Sol–Gel method. The CPAC/Mn3O4 nanocomposite electrode materials were then obtained by calcination of the precursor. FESEM images show that the manganese oxide embedded in the nanocomposite electrode has a nano-rod structure. Electrochemical test results show that the precursor has a relatively good electrochemical performance when the manganese content is 20 wt%. With 20 wt% manganese content in precursor, under a calcining temperature of 500 °C and a calcining time of 3 h, the nanocomposite electrode material exhibits a better electrochemical performance and its specific capacitance reaches up to 277 F g−1.
This work was financially supported by the Funds for Creative Research Groups of China (Grant NO.51121062) and Excellent Young Teachers in Lanzhou University of Technology Training Project (Grant NO.1005ZCX016).
- 4.Z. Sun, K.Y. Liu, H.F. Zhang et al., Acta Phys. Chim. Sin. 25, 1991 (2009)Google Scholar
- 6.S.C. Yan, J.S. Wu, J. Nanjing Univ. Posts Telecommun. (Nat. Sci.). 31, 134 (2011)Google Scholar
- 7.S.J. Li, S.L. Wang, B. Xu, Chin. J. Chem. Eng. 59, 514 (2008)Google Scholar
- 8.E.H. Liu, R. Ding, X.Y. Meng, S.T. Tan, J.C. Zhou, J. Mater. Sci. Mater. Electron. 18, 1179 (2007)Google Scholar
- 9.L.I. Hill, A. Verbaere, D. Guyomard, J. Power Sources 119/121, 226 (2003)Google Scholar
- 10.Z.D. Chen, L. Gao, J.Y. Cao, Acta Chim. Sinica 69, 503 (2011)Google Scholar
- 11.J. Yan, Z.J. Fan, T. Wei, M.L. Zhang, J. Mater. Sci. Mater. Electron. 21, 619 (2010)Google Scholar
- 12.L.F. Wan, X.P. Huang, F. Mao, J. China Three Gorges Univ. (Nat. Sci.). 30, 108 (2008)Google Scholar
- 13.X.Y. Wang, X.Y. Wang, T.L. Hou, Chin. J. Chem. Eng. 57, 442 (2006)Google Scholar
- 15.H.M. Luo, S.R. Yu, H.X. Feng, J. China Coal Soc. 34, 971 (2009)Google Scholar
- 16.H.M. Luo, P. Yang, F.B. Zhang, J. Mater. Sci. Mater. Electron. Online first. doi: 10.1007/s10854-012-0838-y (2012)
- 17.N. Tang, X.K. Tian, C. Yang, Mater. Res. Bull. 71, 258 (2010)Google Scholar
- 18.H. Gui, H.C. Zeng, J. Phys Chem B. 8, 3492 (2004)Google Scholar
- 20.Y.C. Gui, L.W. Qian, X.F. Qian, Chinese. J. Inorg. Chem. 25, 668 (2009)Google Scholar
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