Parametrization of impedance spectra of GC/H2SO4 electrode: trials and errors

Impedance spectra of two differently prepared (polished and anodically oxidized) GC electrodes measured at +0.30 V vs. SCE in 0.5 mol dm(-3) H2SO4 electrolyte have been analysed on the basis of presumed electrical equivalent circuit(s) and complex non-linear least square fitting procedure. Statistical analysis of model residuals and reliability of the estimated values of parameters were used as indicators for correct or incorrect modeling. In such a way, the polished GC electrode has been modeled using not-ideal capacitive element describing relatively flat surface, whereas anodically oxidized GC electrode has been modeled using not-ideal capacitive element loaded by transmision line element representing a porous surface structure.