Models of the impedance of an electrochemical interface
Electrochemical methods - Impedance measurements

The case of quasi-reversible charge transfer, controlled by matter transport, will be considered first. The only reaction taking place at the interface is the redox process: $\text{Ox}+ne\underset{k_{\text{i}}}{\overset{k_{\text{d}}}{\rightleftharpoons }}\text{Red}$

where k_d and k_i are the direct and reverse reaction rates expressed in mol · s^-1· m^-2.

The concentrations c_Red and c_Ox of the Red and Ox species diffusing into and out of the solution satisfy the following equations (known as Fick's second law), derived from equation