Points, explanatory
Toward a More Accurate Understanding of Impedance Behaviors of Randles-type Equivalent Circuits
2018 Volume 64 Issue 2 Pages 91-96
Details
2018 Volume 64 Issue 2 Pages 91-96
On the complex plane, an impedance of a Randles-type equivalent circuit, which is commonly used for the analysis of an electrochemical impedance, traces a semicircle originated from the parallel connection of the charge-transfer resistance (Rct) and the double-layer capacitance (Cdl), and a 45-degree line originated from the Warburg element (ZW). It is often mentioned that there is an “overlap” between the semicircle and the extrapolation of the 45-degree line, and mathematically it has a length of 2⋅σ 2⋅Cdl. Although this is correct, to emphasize the existence of such an “overlap” may mislead the analysis, since its magnitude is extremely small compared with the size of the semicircle, when the figures of the semicircle and line are visibly separated from each other.
