Supercapacitor Behavior of Poly(Carbazole-EDOT) Derivatives/Multi-Walled Carbon Nanotubes, Characterizations and Equivalent Circuit Model Evaluations

Abstract

Three new different comonomers of carbazole-EDOT derivatives had been previously synthesized and characterized in detail. In this study, electroactive materials were electropolymerized onto multi-walled carbon nanotube (MWCNT) modified glassy carbon (GC) electrode in 0.1 M sodium dodecyl sulphate (SDS) solution. The electrochemical impedance spectroscopic results of Nyquist, and Bode-magnitude and Bode-phase plots show that polymers/MWCNT composites possess good capacitive characteristics. P(Com2)/MWCNT/GCE system's specific capacitance was up to Sc = 132.6 F g⁻¹ at the scan rate of 70 mV s⁻¹ from the area formula, Eq. (1). Furthermore, P(Com2)/MWCNT composite had very rapid charge/discharge ability with specific capacitance of Sc = 75.23 F g⁻¹ at DC potential of 0.3 V from Nyquist plot, and Sc = 90.53 F g⁻¹ at the scan rate of 60 mVs⁻¹ from charge formula, Eq. (2), which is important practical advantage. In addition, such composite had a good cycling performance and a wide potential window. Long-term stability of the capacitor was also tested by CV, and the results indicated that, after 500 cycles, the specific capacitance was still at ∼100.0%, ∼89%, and ∼97.0% of the initial capacitance for P(Com1)/MWCNT, P(Com2)/MWCNT, and P(Com3)/MWCNT, respectively. An equivalent circuit model of R_s(C₁(R₁(Q(R₂W))))(C_GCR_GC) was obtained to fit the experimental and theoretical data. Solution resistance (Rs) and resistance from GCE decrease gradually. However, capacitance of film (C₁), constant phase element (Q), and n values increase for P(Com1), P(Com2), and P(Com3)/MWCNT, respectively. Therefore, more homogeneous and less rough surface composite film was obtained by addition of MWCNT in the composite material.

Keywords:

• Carbon nanotube
• Functional polymer
• Pseudo-capacitance
• Specific capacitance
• Supercapacitor
• Synthesis

ACKNOWLEDGMENTS

The authors wish to thank Serhat Tıkız (Afyon Kocatepe Uni., TUAM, Afyon, Turkey) for recording SEM-EDX measurements. The authors also thank Yakup Bakis (BINATAM, Fatih University, Istanbul, Turkey) for recording AFM images.

Notes

Values range from −0.1 V to 0.4 V for P(Com1), P(Com2), and P(Com3)/MWCNT/GCE. ([Kom1]₀ = 5 mM, 1.3 V, 300 s), ([Kom2]₀ = 1 mM, 1.2 V, 100 s), and ([Kom3]₀ = 2 mM, 1.3 V, 75 s). 0.3 V means the highest specific capacitances were obtained for nanocomposite film.

Values range from 5 mV s⁻¹ to 100 mV s⁻¹ for P(Com1), P(Com2), and P(Com3)/MWCNT/GCE. ([Kom1]₀ = 5 mM, 1.3 V, 300 s), ([Kom2]₀ = 1 mM, 1.2 V, 100 s), and ([Kom3]₀ = 2 mM, 1.3 V, 75 s). 70 mV/s means the highest specific capacitances were obtained for nanocomposite films.

Values range from 5 mV s⁻¹ to 100 mV s⁻¹ for P(Com1), P(Com2), and P(Com3)/MWCNT/GCE. ([Kom1]₀ = 5 mM, 1.3 V, 300 s), ([Kom2]₀ = 1 mM, 1.2 V, 100 s), and ([Kom3]₀ = 2 mM, 1.3 V, 75 s). 60 mV/s means the highest specific capacitances were obtained for nanocomposite films.

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