Electrochemical impedance spectroscopy (EIS) is an effective method
for characterization of electrode processes. Complex plane (Nyquist)
plots of the EIS are often utilized for an easy estimate of the circuit elements.
These plots include a semicircle portion and a linear portion. The
Nyquist diameter is equal to the charge transfer resistance, Rct. Fig. 5A
and B displays the Nyquist diagram of the carbon paste electrode in
the absence and presence of SDS in solution, respectively. As we could
notice, the visible decrease in the diameter of semicircle would happen.
Rct decrease from 8.64 × 105 Ω cm2 for CPE in the absence of SDS to
1.65 × 105 Ω cm2 in the presence of SDS.