Poly(2,6-di(thiophene-2-yl)-3,5bis(4-(thiophene-2-yl)phenyl)dithieno [3,2-b;2',3'-d]thiophene)/carbon nanotube composite for capacitor applications

A novel monomer, 2,6-di(thiophene-2-yl)-3,5bis(4-(thiophene-2-yl)phenyl) dithieno[3,2-b;2',3'-d]thiophene (Th₄DTT) has been synthesized and used as an electro-active material. It has been electropolymerized onto glassy carbon (GC) electrode in sodium dodecyl sulfate (SDS) solution (0.1 M) together with multi-walled carbon nanotubes (MWCNT). A good capacitive characteristics for P(Th₄DTT)/MWCNT composite has been obtained by electrochemical impedance spectroscopy (EIS), which is, to our best knowledge, the first report on capacitor behavior of a dithienothiophene. A synergistic effect has been resolved by Nyquist, Bode-magnitude - phase and admittance plots. Specific capacitance of the conducting polymer/MWCNT, calculated from cyclic voltammogram (CV) together with area and charge formulas, has been found to be 20.17 F g^-1. Long-term stability of the capacitor has also been tested by CV, and the results indicated that, after 500 cycles, the specific capacitance is 87.37% of the initial capacitance. An equivalent circuit model of R _s(C₁(R₁(Q(R₂W))))(C ₂R₃) has been obtained to fit the experimental and theoretical data. The double layer capacitance (C_dl) value of P(Th₄DTT)/MWCNT (4.43 mF cm^-2) has been found to be 25 times higher than P(Th₄DTT) (C_dl= 0.18 mF cm ^-2).