- Email: [email protected]
MnO2 composite networks deposited on graphite felt as free-standing electrode for supercapacitors
Materials Letters 104 (2013) 48–52
Contents lists available at SciVerse ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Three-dimensional polypyrrole/MnO2 composite networks deposited on graphite felt as free-standing electrode for supercapacitors Mingping He a, Yuying Zheng b,n, Qifeng Du b a b
College of Chemistry and Chemical Engineering, Fuzhou University, Fuzhou 350108, China College of Materials Science and Engineering, Fuzhou University, Fuzhou 350108, China
art ic l e i nf o
a b s t r a c t
Article history: Received 23 January 2013 Accepted 3 April 2013 Available online 11 April 2013
Polypyrrole/MnO2 composites with unique three-dimensional network structure were successfully deposited on graphite felt (GF) fibers at the temperature of 50 1C to fabricate PYMG-HT composite, which can be used as a free-standing electrode for supercapacitors. For comparison, PYMG-LT electrode was also prepared in ice bath, and the polypyrrole/MnO2 deposits on GF prepared at 0 1C exhibit nanoflower shape, which is different from PYMG-HT. The PYMG-HT electrode displays specific capacitance as high as 821.3 F g−1 at the current density of 0.5 A g−1, which is much higher than that of PPy/MnO2 reported previously. Moreover, the PYMG-HT exhibits enhanced capacitive performance compared to PYMG-LT electrode. & 2013 Elsevier B.V. All rights reserved.
Keywords: Polymers Composite materials Electrical properties
1. Introduction Manganese dioxide (MnO2) is the most promising material for supercapacitors owing to its low cost and high theoretical specific capacitance value (1370 F g−1) [1,2]. However, the actual capacitance of MnO2 is far away from its theoretical value and the capacitance drops rapidly with the increase of loading amount, which may be ascribed to its poor electronic conductivity and low utilization [3]. In order to improve the performance of MnO2, an effective method is to incorporate MnO2 into electrically conductive materials, such as carbonaceous materials and conducting polymers [4–10]. But most of the attempts are based on low mass loading of MnO2, which hinders its practical applications. Another problem is that the composite materials reported previously were mostly powder-based, and during the making process of electrode, dead volume would arise from the dense aggregation of active materials and the use of a binder would reduce the conductivity of the electrode. To solve this problem, active materials can be directly grown on free-standing substrates. Compared to flat substrates, three-dimensional (3D) porous free standing conductive substrates with larger surface area for high mass loading of active materials may be more promising substrates. Graphite felt (GF) is attractive due to its 3D porous structure and reasonable electrical conductivity. In this work, polypyrrole/MnO2 composite with unique 3D network structure was successfully deposited on GF substrate to
n
Corresponding author. Tel./fax: +86 591 22866529. E-mail addresses: [email protected] (M. He), [email protected] (Y. Zheng). 0167-577X/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.matlet.2013.04.008
fabricate PYMG-HT free-standing electrode at the temperature of 50 1C. The PYMG-HT electrode exhibited excellent specific capacitance, which was investigated by electrochemical technique. 2. Experimental 2.1. Materials Pyrrole was purified by distillation under reduced pressure prior to use. All other reagents used in the experiment were of analytical grade and were used without further purification. 2.2. Pretreatment of graphite felt GF was cleaned with acetone followed by electrochemical oxidation carried out in 0.5 M H2SO4 at a constant potential of 2 V for 300 s. This electrochemical pretreatment was conducted on a CHI660D Electrochemical Workstation (Chenhua, China) using a conventional three-electrode electrochemical system which consists of a piece of GF as the working electrode, Pt wire as the counter electrode, and Ag/AgCl (in 3 M KCl solution) as the reference electrode. 2.3. Preparation of polypyrrole/MnO2/graphite felt composites In a typical procedure of the synthesis, the pretreated GF was immersed into 0.1 M pyrrole acetone solution to absorb the pyrrole monomer. After drying naturally for 0.5 h, the sample was dipped into 0.1 M potassium permanganate (KMnO4) acidic solution whose pH value was adjusted to 1 by hydrochloride acid.
M. He et al. / Materials Letters 104 (2013) 48–52
The in-situ reaction was carried out at 50 1C for 1 h. The resulting product was rinsed using deionized water and ethanol several times to remove the residual reactants and dried at 60 1C for 12 h to obtain the final product denoted as PYMG-HT. And the areal mass loading of PPy/MnO2 is about 3 mg cm−2. While maintaining the other parameters, sample PYMG-LT was also obtained by carrying out the whole reaction process at 0 1C.
49
Na2SO4 as electrolyte, with N2 purging for 10 min before the measurements. The specific capacitance can be calculated by the equation (1). C¼
It mV
ð1Þ
where C is the specific capacitance, I is the current density, t is the discharge time, m is the weight of PPy/MnO2, and V is the efficient potential window.
2.4. Characterization The samples were investigated by FTIR (Perkin Elmer Spectrum 2000), XPS (Thermo Scientific ESCALAB 250), FE-SEM (Nova NanoSEM 230) and TEM (FEI Tecnai G2). All electrochemical measurements were performed at room temperature in a threeelectrode electrochemical system mentioned above using 0.5 M
3. Results and discussion The corresponding morphologies of the samples were characterized by FE-SEM as shown in Fig. 1. Fig. 1a and b depicts the SEM images of GF, indicating that GF microfibers construct a
Fig. 1. FESEM images of GF (a, b), PYMG-HT (c, d) and PYMG-LT (e, f).
50
M. He et al. / Materials Letters 104 (2013) 48–52
three-dimensional configuration and its surface is very smooth. The SEM images of PYMG-HT are shown in Fig. 1c and d, which reveal a unique three-dimensional network structure of polypyrrole/MnO2 deposits on the surface of GF fiber. When the experimental process is carried out at the temperature of 0 1C, the morphology of the as-prepared sample (PYMG-LT) is entirely different from that of PYMG-HT. It can be seen from Fig. 1e and f that polypyrrole/MnO2 nanoflowers were deposited on the surface of GF fiber. TEM images of the obtained composites are presented in Fig. 2. In the case of PYMG-HT, PPy/MnO2 nanoshell with a thickness of around 100 nm is deposited on the surface of GF fibers, while for PYMG-LT, the thickness of PPy/MnO2 nanoshell is around 50 nm. Furthermore, in both cases, it can be observed that the MnO2 is
embedded as a molecular level dispersion into the PPy matrix because there is no distinct boundary between MnO2 and PPy. Fig. 3a shows the FTIR spectra of PYMG-HT composite. All of the characteristic absorption peaks of PPy can be observed clearly. 1578 cm−1 can be attributed to pyrrole ring vibration. The bands at 1286 cm−1 and 1069 cm−1 are assigned to QC–H in-plane vibration. 1174 cm−1 and 948 cm−1 are for bipolaron of doped PPy. The bands located at 850 cm−1 and 656 cm−1 are attributed to aromatic C–H out-of-plane vibration [11–16]. Fig. 3b displays the full spectrum which shows the signals from Mn, O, N and C elements, indicating the existence of MnO2, PPy and GF. The Mn 2p core level spectrum (Fig. 3c) presents two peaks centered at the binding energies of 641.9 eV and 653.7 eV,
Fig. 2. TEM images of PYMG-HT (a) and PYMG-LT (b).
Fig. 3. (a) FTIR spectra, (b) XPS full spectrum, (c) Mn 2p core level XPS spectra and (d) O 1s core level XPS spectra of PYMG-HT.
M. He et al. / Materials Letters 104 (2013) 48–52
51
Fig. 4. (a) Cyclic voltammograms of PYMG-HT and PYMG-LT at a scan rate of 50 mV s−1; (b) charge and discharge curves of PYMG-HT electrode at different current densities; (c) charge and discharge curves of PYMG-LT electrode at different current densities; and (d) Nyquist plots of the EIS for PYMG-HT and PYMG-LT electrodes.
which can be ascribed to Mn 2p3/2 and Mn 2p1/2, respectively. The spin energy separation is 11.8 eV, which is in good agreement with the previously reported data for MnO2 [17,18]. As shown in Fig. 3d, XPS spectrum of O1s core-level can be fitted with three components which are related to the Mn–O–Mn bond (529.96 eV) for the tetravalent oxide, the Mn–O–H bond (531.56 eV) for a hydrated trivalent oxide, and the H–O–H bond (533.11 eV) for residual water, respectively. Cyclic voltammogram (CV) and galvanostatic charge/discharge measurement were employed to evaluate the electrochemical performance of the fabricated electrodes. Fig. 4a shows the CV curves of the PYMG-HT and PYMG-LT electrodes at a scan rate of 50 mV s−1. The CV curve of the PYMG-HT electrode exhibits better rectangular and symmetric shape compared to PYMG-LT, suggesting fast reversible Faradic reactions and ideal capacitive behavior of PYMG-HT. Fig. 4b displays the galvanostatic charge/discharge curves of PYMG-HT at different current densities, which are symmetrical, indicating good capacitive performance. GF has low capacitance and contributes negligibly to the overall capacitance of the electrode [19]. The specific capacitance of PYMG-HT based on PPy/MnO2 is calculated to be 821.3 F g−1 at the current density of 0.5 A g−1, which is much higher than that of the PPy-based and MnO2-based materials reported previously [20–23]. The galvanostatic charge/discharge curves of PYMG-LT are presented in Fig. 4c. And the specific capacitance of PYMG-LT is 650 F g−1 at the current density of 0.5 A g−1. The PYMG-HT electrode exhibits much larger specific capacitance than PYMG-LT, which may be ascribed to the unique 3D network structure of polypyrrole/MnO2 deposits, facilitating easy access of electrolytes to the active materials. Fig. 4d shows the resulting Nyquist plots of the EIS spectra for the PYMGHT and PYMG-LT electrodes. Both of the curves are composed of
an arc in the high frequency region and a straight line in the low frequency range. The diameter of the arc in the curve of PYMG-HT is much smaller than that of PYMG-LT, which shows that charges can transfer more easily in PYMG-HT, since the diameter of the arc corresponds to the charge-transfer resistance of the electrode.
4. Conclusions Polypyrrole/MnO2/graphite felt composite (PYMG-HT) which can be used as a free-standing electrode for supercapacitors was fabricated via a simple in-situ redox reaction at the temperature of 50 1C. The polypyrrole/MnO2 composites deposited on graphite felt (GF) construct a unique three-dimensional network structure. For comparison, polypyrrole/MnO2 composites with nanoflower shape were also deposited on GF fibers at the temperature of 0 1C to fabricate PYMG-LT electrode. PYMG-HT composite displays large specific capacitance as high as 821.3 F g−1 at the current density of 0.5 A g−1, which is much larger than that of PPy/MnO2 reported previously. Moreover, the PYMG-HT exhibits enhanced specific capacitance compared to PYMG-LT (650 F g−1), which may be ascribed to the unique network structure of polypyrrole/MnO2 deposits facilitating the easy access of electrolyte to the composites and leading to enhancement of the capacitive performance. Therefore, PYMG-HT can serve as a promising free-standing electrode for supercapacitors.
Acknowledgments This work was supported by Educational Office of Fujian Province (Grant no. JK2011004).
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M. He et al. / Materials Letters 104 (2013) 48–52
References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11]
Toupin M, Brousse T, Belanger D. Chem Mater 2004;16:3184–90. Wei W, Cui X, Chen W, Ivey DG. Chem Soc Rev 2011;40:1697–721. Pang SC, Anderson MA, Chapman TW. J Electrochem Soc 2000;147:444–50. Cheng Q, Tang J, Ma J, Zhang H, Shiya N, Qin LC. Carbon 2011;49:2917–25. Liu J, Essner J, Li J. Chem Mater 2010;22:5022–30. Fischer AE, Pettigrew KA, Rolison DR, Stroud RM, Long JM. Nano Lett 2007;7:281–6. Bordjiba T, Belanger D. Electrochim Acta 2010;55:3428–33. Liu R, Duay J, Lee SB. ACS Nano 2010;4:4299–307. Lu Q, Zhou Y. J Power Sources 2011;196:4088–94. Jafri JRI, Mishra AK, Ramaprabhu S. J Mater Chem 2011;21:17601–5. Cheng QL, Pavlinek V, Li CZ, Lengalova A, He Y, Saha P. Appl Surf Sci 2006;253:1736–40.
[12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23]
Ballav N, Biswas M. Mater Lett 2006;60:514–7. Zhang WX, Wen XG, Yang SH. Langmuir 2003;19:4420–6. Xu J, Li XL, Liu JF, Wang X, Peng Q, Li YD. J Polym Sci Part A 2005;43:2892–900. Chen AH, Xie HX, Wang HQ, Li HY, Li XY. Synth Met 2006;156:346–50. Omastva M, Trchova M, Kovarova J, Stejskal J. Synth Met 2003;138:447–55. Lee SW, Kim J, Chen S, Hammond PT, Yang SH. ACS Nano 2010;4:3889–96. Li Q, Liu J, Zou J, Chunder A, Chen Y, Zhai L. J Power Sources 2011;196:565–72. He MP, Zheng YY, Du QF, Polym Compos, in press. DOI 10.1002/pc.22481. Zang JF, Li XD. J Mater Chem 2011;21:10965–9. Bao LH, Zang JF, Li XD. Nano Lett 2011;11:1215–20. Bao LH, Li XD. Adv Mater 2012;24:3246–52. Dubal DP, Lee SH, Kim JG, Kim WB, Lokhande CD. J Mater Chem 2012;22:3044–52.
Contents lists available at SciVerse ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Three-dimensional polypyrrole/MnO2 composite networks deposited on graphite felt as free-standing electrode for supercapacitors Mingping He a, Yuying Zheng b,n, Qifeng Du b a b
College of Chemistry and Chemical Engineering, Fuzhou University, Fuzhou 350108, China College of Materials Science and Engineering, Fuzhou University, Fuzhou 350108, China
art ic l e i nf o
a b s t r a c t
Article history: Received 23 January 2013 Accepted 3 April 2013 Available online 11 April 2013
Polypyrrole/MnO2 composites with unique three-dimensional network structure were successfully deposited on graphite felt (GF) fibers at the temperature of 50 1C to fabricate PYMG-HT composite, which can be used as a free-standing electrode for supercapacitors. For comparison, PYMG-LT electrode was also prepared in ice bath, and the polypyrrole/MnO2 deposits on GF prepared at 0 1C exhibit nanoflower shape, which is different from PYMG-HT. The PYMG-HT electrode displays specific capacitance as high as 821.3 F g−1 at the current density of 0.5 A g−1, which is much higher than that of PPy/MnO2 reported previously. Moreover, the PYMG-HT exhibits enhanced capacitive performance compared to PYMG-LT electrode. & 2013 Elsevier B.V. All rights reserved.
Keywords: Polymers Composite materials Electrical properties
1. Introduction Manganese dioxide (MnO2) is the most promising material for supercapacitors owing to its low cost and high theoretical specific capacitance value (1370 F g−1) [1,2]. However, the actual capacitance of MnO2 is far away from its theoretical value and the capacitance drops rapidly with the increase of loading amount, which may be ascribed to its poor electronic conductivity and low utilization [3]. In order to improve the performance of MnO2, an effective method is to incorporate MnO2 into electrically conductive materials, such as carbonaceous materials and conducting polymers [4–10]. But most of the attempts are based on low mass loading of MnO2, which hinders its practical applications. Another problem is that the composite materials reported previously were mostly powder-based, and during the making process of electrode, dead volume would arise from the dense aggregation of active materials and the use of a binder would reduce the conductivity of the electrode. To solve this problem, active materials can be directly grown on free-standing substrates. Compared to flat substrates, three-dimensional (3D) porous free standing conductive substrates with larger surface area for high mass loading of active materials may be more promising substrates. Graphite felt (GF) is attractive due to its 3D porous structure and reasonable electrical conductivity. In this work, polypyrrole/MnO2 composite with unique 3D network structure was successfully deposited on GF substrate to
n
Corresponding author. Tel./fax: +86 591 22866529. E-mail addresses: [email protected] (M. He), [email protected] (Y. Zheng). 0167-577X/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.matlet.2013.04.008
fabricate PYMG-HT free-standing electrode at the temperature of 50 1C. The PYMG-HT electrode exhibited excellent specific capacitance, which was investigated by electrochemical technique. 2. Experimental 2.1. Materials Pyrrole was purified by distillation under reduced pressure prior to use. All other reagents used in the experiment were of analytical grade and were used without further purification. 2.2. Pretreatment of graphite felt GF was cleaned with acetone followed by electrochemical oxidation carried out in 0.5 M H2SO4 at a constant potential of 2 V for 300 s. This electrochemical pretreatment was conducted on a CHI660D Electrochemical Workstation (Chenhua, China) using a conventional three-electrode electrochemical system which consists of a piece of GF as the working electrode, Pt wire as the counter electrode, and Ag/AgCl (in 3 M KCl solution) as the reference electrode. 2.3. Preparation of polypyrrole/MnO2/graphite felt composites In a typical procedure of the synthesis, the pretreated GF was immersed into 0.1 M pyrrole acetone solution to absorb the pyrrole monomer. After drying naturally for 0.5 h, the sample was dipped into 0.1 M potassium permanganate (KMnO4) acidic solution whose pH value was adjusted to 1 by hydrochloride acid.
M. He et al. / Materials Letters 104 (2013) 48–52
The in-situ reaction was carried out at 50 1C for 1 h. The resulting product was rinsed using deionized water and ethanol several times to remove the residual reactants and dried at 60 1C for 12 h to obtain the final product denoted as PYMG-HT. And the areal mass loading of PPy/MnO2 is about 3 mg cm−2. While maintaining the other parameters, sample PYMG-LT was also obtained by carrying out the whole reaction process at 0 1C.
49
Na2SO4 as electrolyte, with N2 purging for 10 min before the measurements. The specific capacitance can be calculated by the equation (1). C¼
It mV
ð1Þ
where C is the specific capacitance, I is the current density, t is the discharge time, m is the weight of PPy/MnO2, and V is the efficient potential window.
2.4. Characterization The samples were investigated by FTIR (Perkin Elmer Spectrum 2000), XPS (Thermo Scientific ESCALAB 250), FE-SEM (Nova NanoSEM 230) and TEM (FEI Tecnai G2). All electrochemical measurements were performed at room temperature in a threeelectrode electrochemical system mentioned above using 0.5 M
3. Results and discussion The corresponding morphologies of the samples were characterized by FE-SEM as shown in Fig. 1. Fig. 1a and b depicts the SEM images of GF, indicating that GF microfibers construct a
Fig. 1. FESEM images of GF (a, b), PYMG-HT (c, d) and PYMG-LT (e, f).
50
M. He et al. / Materials Letters 104 (2013) 48–52
three-dimensional configuration and its surface is very smooth. The SEM images of PYMG-HT are shown in Fig. 1c and d, which reveal a unique three-dimensional network structure of polypyrrole/MnO2 deposits on the surface of GF fiber. When the experimental process is carried out at the temperature of 0 1C, the morphology of the as-prepared sample (PYMG-LT) is entirely different from that of PYMG-HT. It can be seen from Fig. 1e and f that polypyrrole/MnO2 nanoflowers were deposited on the surface of GF fiber. TEM images of the obtained composites are presented in Fig. 2. In the case of PYMG-HT, PPy/MnO2 nanoshell with a thickness of around 100 nm is deposited on the surface of GF fibers, while for PYMG-LT, the thickness of PPy/MnO2 nanoshell is around 50 nm. Furthermore, in both cases, it can be observed that the MnO2 is
embedded as a molecular level dispersion into the PPy matrix because there is no distinct boundary between MnO2 and PPy. Fig. 3a shows the FTIR spectra of PYMG-HT composite. All of the characteristic absorption peaks of PPy can be observed clearly. 1578 cm−1 can be attributed to pyrrole ring vibration. The bands at 1286 cm−1 and 1069 cm−1 are assigned to QC–H in-plane vibration. 1174 cm−1 and 948 cm−1 are for bipolaron of doped PPy. The bands located at 850 cm−1 and 656 cm−1 are attributed to aromatic C–H out-of-plane vibration [11–16]. Fig. 3b displays the full spectrum which shows the signals from Mn, O, N and C elements, indicating the existence of MnO2, PPy and GF. The Mn 2p core level spectrum (Fig. 3c) presents two peaks centered at the binding energies of 641.9 eV and 653.7 eV,
Fig. 2. TEM images of PYMG-HT (a) and PYMG-LT (b).
Fig. 3. (a) FTIR spectra, (b) XPS full spectrum, (c) Mn 2p core level XPS spectra and (d) O 1s core level XPS spectra of PYMG-HT.
M. He et al. / Materials Letters 104 (2013) 48–52
51
Fig. 4. (a) Cyclic voltammograms of PYMG-HT and PYMG-LT at a scan rate of 50 mV s−1; (b) charge and discharge curves of PYMG-HT electrode at different current densities; (c) charge and discharge curves of PYMG-LT electrode at different current densities; and (d) Nyquist plots of the EIS for PYMG-HT and PYMG-LT electrodes.
which can be ascribed to Mn 2p3/2 and Mn 2p1/2, respectively. The spin energy separation is 11.8 eV, which is in good agreement with the previously reported data for MnO2 [17,18]. As shown in Fig. 3d, XPS spectrum of O1s core-level can be fitted with three components which are related to the Mn–O–Mn bond (529.96 eV) for the tetravalent oxide, the Mn–O–H bond (531.56 eV) for a hydrated trivalent oxide, and the H–O–H bond (533.11 eV) for residual water, respectively. Cyclic voltammogram (CV) and galvanostatic charge/discharge measurement were employed to evaluate the electrochemical performance of the fabricated electrodes. Fig. 4a shows the CV curves of the PYMG-HT and PYMG-LT electrodes at a scan rate of 50 mV s−1. The CV curve of the PYMG-HT electrode exhibits better rectangular and symmetric shape compared to PYMG-LT, suggesting fast reversible Faradic reactions and ideal capacitive behavior of PYMG-HT. Fig. 4b displays the galvanostatic charge/discharge curves of PYMG-HT at different current densities, which are symmetrical, indicating good capacitive performance. GF has low capacitance and contributes negligibly to the overall capacitance of the electrode [19]. The specific capacitance of PYMG-HT based on PPy/MnO2 is calculated to be 821.3 F g−1 at the current density of 0.5 A g−1, which is much higher than that of the PPy-based and MnO2-based materials reported previously [20–23]. The galvanostatic charge/discharge curves of PYMG-LT are presented in Fig. 4c. And the specific capacitance of PYMG-LT is 650 F g−1 at the current density of 0.5 A g−1. The PYMG-HT electrode exhibits much larger specific capacitance than PYMG-LT, which may be ascribed to the unique 3D network structure of polypyrrole/MnO2 deposits, facilitating easy access of electrolytes to the active materials. Fig. 4d shows the resulting Nyquist plots of the EIS spectra for the PYMGHT and PYMG-LT electrodes. Both of the curves are composed of
an arc in the high frequency region and a straight line in the low frequency range. The diameter of the arc in the curve of PYMG-HT is much smaller than that of PYMG-LT, which shows that charges can transfer more easily in PYMG-HT, since the diameter of the arc corresponds to the charge-transfer resistance of the electrode.
4. Conclusions Polypyrrole/MnO2/graphite felt composite (PYMG-HT) which can be used as a free-standing electrode for supercapacitors was fabricated via a simple in-situ redox reaction at the temperature of 50 1C. The polypyrrole/MnO2 composites deposited on graphite felt (GF) construct a unique three-dimensional network structure. For comparison, polypyrrole/MnO2 composites with nanoflower shape were also deposited on GF fibers at the temperature of 0 1C to fabricate PYMG-LT electrode. PYMG-HT composite displays large specific capacitance as high as 821.3 F g−1 at the current density of 0.5 A g−1, which is much larger than that of PPy/MnO2 reported previously. Moreover, the PYMG-HT exhibits enhanced specific capacitance compared to PYMG-LT (650 F g−1), which may be ascribed to the unique network structure of polypyrrole/MnO2 deposits facilitating the easy access of electrolyte to the composites and leading to enhancement of the capacitive performance. Therefore, PYMG-HT can serve as a promising free-standing electrode for supercapacitors.
Acknowledgments This work was supported by Educational Office of Fujian Province (Grant no. JK2011004).
52
M. He et al. / Materials Letters 104 (2013) 48–52
References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11]
Toupin M, Brousse T, Belanger D. Chem Mater 2004;16:3184–90. Wei W, Cui X, Chen W, Ivey DG. Chem Soc Rev 2011;40:1697–721. Pang SC, Anderson MA, Chapman TW. J Electrochem Soc 2000;147:444–50. Cheng Q, Tang J, Ma J, Zhang H, Shiya N, Qin LC. Carbon 2011;49:2917–25. Liu J, Essner J, Li J. Chem Mater 2010;22:5022–30. Fischer AE, Pettigrew KA, Rolison DR, Stroud RM, Long JM. Nano Lett 2007;7:281–6. Bordjiba T, Belanger D. Electrochim Acta 2010;55:3428–33. Liu R, Duay J, Lee SB. ACS Nano 2010;4:4299–307. Lu Q, Zhou Y. J Power Sources 2011;196:4088–94. Jafri JRI, Mishra AK, Ramaprabhu S. J Mater Chem 2011;21:17601–5. Cheng QL, Pavlinek V, Li CZ, Lengalova A, He Y, Saha P. Appl Surf Sci 2006;253:1736–40.
[12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23]
Ballav N, Biswas M. Mater Lett 2006;60:514–7. Zhang WX, Wen XG, Yang SH. Langmuir 2003;19:4420–6. Xu J, Li XL, Liu JF, Wang X, Peng Q, Li YD. J Polym Sci Part A 2005;43:2892–900. Chen AH, Xie HX, Wang HQ, Li HY, Li XY. Synth Met 2006;156:346–50. Omastva M, Trchova M, Kovarova J, Stejskal J. Synth Met 2003;138:447–55. Lee SW, Kim J, Chen S, Hammond PT, Yang SH. ACS Nano 2010;4:3889–96. Li Q, Liu J, Zou J, Chunder A, Chen Y, Zhai L. J Power Sources 2011;196:565–72. He MP, Zheng YY, Du QF, Polym Compos, in press. DOI 10.1002/pc.22481. Zang JF, Li XD. J Mater Chem 2011;21:10965–9. Bao LH, Zang JF, Li XD. Nano Lett 2011;11:1215–20. Bao LH, Li XD. Adv Mater 2012;24:3246–52. Dubal DP, Lee SH, Kim JG, Kim WB, Lokhande CD. J Mater Chem 2012;22:3044–52.