Randles equivalent circuit, diagram

By taking into account the double-layer capacity, Q, and the electrolyte resistance, Re, one obtains the Randles equivalent circuit [150] (Fig. 10), where the faradaic impedance Zp is represented by the transfer resistance Rt in series with the Warburg impedance W. It can be shown that the high-frequency part of the impedance diagram plotted in the complex plane (Nyquist plane) is a semicircle representing Rt in parallel with Cd and the low-frequency part is a Warburg impedance. 

Figure 6. Randles equivalent circuit and complex plane diagram for activation control.

Idealised Nyquist diagram corresponding to the equivalent circuit of Ershler-Randles (Fig.2.6). 

Figure 8-11. Equivalent circuit of a polarized electrode obtained by modification of the Randles diagram, where / s is the electrolyte resistance, Q the double layer capacity, R, the charge transfer resistance, Rg the anodic process resistance, R the cathodic process resistance, CPE the constant phase element, and the diffusion impedance.

A prototypical equivalent circuit for electrochemical systems is the Randles circuit illustrated in Fig. 20.25. The circuit is contained in Fig. 20.25a, and the corresponding complex plane diagram is shown in Fig. 20.25b. This particular circuit shares some of the fea-... 

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