Fig. 3.
General scheme of a Nyquist plot and its Randles’ equivalent circuit: a Nyquist plot emerges from plotting the imaginary (capacitive) against real (resistive) components of impedance. Most relevant features are: resistance of the solution Rs; charge transfer resistance Rct; the maximum double-layer capacitance Cdl and the Warburg impedance W, which is only observed in Faradaic sensors and represents mass transfer diffusion effects. b Randles’ equivalent circuit representing an electrical circuit modelling a Faradaic sensor