Experimental Issues Associated with Measurement of Local Electrochemical Impedance

A detailed analysis from both numerical calculations and experimental results is presented for the local electrochemical impedance spectroscopy (LEIS) measurements of a disk electrode, which accounted for the placement of the LEIS probe above the electrode surface. The calculations for an electrode with a local constant phase element behavior were in excellent agreement with experimental observations for a stainless steel electrode in a (pH 4) electrolyte. Measurement of the local impedance at two positions above the electrode surface allowed estimations of the local interfacial impedance and the local ohmic impedance, which were in excellent agreement with the simulations. The results demonstrate that the local impedance measurement itself cannot be used to estimate the surface area sampled by the LEIS probe. The area sampled must be determined instead by the probe geometry.