An Explanation for Depressed Semi-circular Arcs in Interfacial Impedance Plots of the Interface between Metal and Electrolyte

Abstract

A new electrical equivalent circuit accounting for metal/solution interface about the surface heterogeneity of electrodes was proposed instead of the known semi-circular law. The present equivalent model consists of a ladder network of elements, where each element is made of a solution resistance in series with a parallel combination of double layer of capacitance and charge transfer resistance. The parameter σ, the standard deviation of normal distribution of double layer capacitance affected the depressed semi-circular arcs of different extent, which may be caused by various heterogeneities of the surface reactivity. The circuit which gives a depressed semi-circular arc is in agreement with the results of electrodeposition of copper from acidic copper sulphate solution.