Capacitive behavior of polycarbazole- and poly(N-vinylcarbazole)-coated carbon fiber microelectrodes in various solutions

The electrochemical behavior of polycarbazole (PCz) and poly(N-vinyl carbazole) P(NVCz) was investigated by means of electrochemical impedance spectroscopy (EIS). Supporting electrolytes made from various combinations of solvents (acetonitrile and propylene carbonate) and salts (sodium perchlorate, lithium perchlorate, and tetraethyl ammonium perchlorate) were employed in the investigation. Information on the double layer capacitance (C_dl) and specific capacitance (C_sp) of P(NVCz) was achieved by cyclic voltammetry (CV), chronoamperometry and chronopotentiometry. Carbon fiber microelectrodes (CFME) were electrocoated by cyclic voltammetry in a monomer-free solution and displayed film thicknesses in the range ~200 nm to ~4.8 μm. The capacitive behavior of the PCz- and P(NVCz)-coated carbon fiber microelectrodes was also investigated by CV. The effects of the type of electrolyte and solvent on the electrochemical impedance spectroscopic data were subsequently fitted with an ((R(C(R(Q(RW))))(CR))-equivalent circuit model to calculate the numerical values of the proposed components. The obtained experimental C_sp values for PCz/CFME and P(NVCz)/CFME, as measured in LiClO₄/ACN, were 280.5 mF g⁻¹ and 294.1 mF g⁻¹, respectively.