Local Electrochemical Impedance Spectroscopy: Correlation with Global Impedance Measurements

Electrochemical techniques such as cyclic voltammetry or electrochemical impedance spectroscopy (EIS) are widely used for investigating the kinetics of heterogeneous electron-transfer reactions, co upled chemical reactions, or adsorption processes. In such conventional electrochemical experiments, the electrode response to a perturbation signal corresponds to a surface-averaged measurement, whereas the electrochemical systems rarely exhibits such an ideal behavior, and this can lead to difficulties with data interpretation. Among the various local techniques devised for investigating electrochemical processes on a local scale, local electrochemical impedance spectroscopy (LEIS) [1, 2] is very promising since it combines the advantage of a transient analysis with the use of potentiometric probes. In a recent series of papers [3-5], our group revisited the basis of the LEIS technique. A key contribution was the definition of three local impe dances. The local interfacial impedance (z0) was defined to involve both a local current density and the local potential drop across the diffuse double layer. The local Ohmic impedance (ze) was defined to involve a local current density and potential drop from the outer region of the diffuse double layer to the distant reference electrode. The local impedance ( z) was thus the sum of the local interfacial impedance and the local Ohmic impedance. All these measurements can be performed simultaneously with the experimental setup depicted in Fig. 1.