A voltammetric and electrochemical impedance study of glassy carbon electrodes galvanostatically coated with approximately 23 nm of polycarbazole (GC/PCZ) was conducted in various concentrations of aqueous H2SO4 and KNO3 and their mixtures. Cyclic voltammetry showed strong dependencies on both the electrolyte type and concentration, while the impedance characteristics were influenced much less. This was shown to be due to strong ion transport effects in voltammetry which became insignificant in the small amplitude impedance experiments, which were dominated by electron transport though the polycarbazole layer. Thus combination of the two techniques provided a more complete description of the polycarbazole electrochemistry. Both techniques provided evidence of cation insertion which extended the range of electroactivity to lower potentials at high KNO3 concentrations and when both KNO3 and H2SO4 were present. (C) 2014 Elsevier Ltd. All rights reserved.