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 0.1M 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=132.6Fg(-1) at the scan rate of 70mVs(-1) from the area formula, Eq. (1). Furthermore, P(Com2)/MWCNT composite had very rapid charge/discharge ability with specific capacitance of Sc=75.23Fg(-1) at DC potential of 0.3V from Nyquist plot, and Sc=90.53Fg(-1) at the scan rate of 60mVs(-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 500cycles, the specific capacitance was still at approximate to 100.0%, approximate to 89%, and approximate to 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(C-1(R-1(Q(R2W))))(CGCRGC) was obtained to fit the experimental and theoretical data. Solution resistance (Rs) and resistance from GCE decrease gradually. However, capacitance of film (C-1), 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.