Influence of Micrometric-Scale Electrode Heterogeneity on Electrochemical Impedance Spectroscopy

Numerical simulations for a disk electrode show that the frequency at which time-constant dispersion appears depends on the characteristic dimension of the feature causing the dispersion. The characteristic dimension for a disk is the radius; for roughness, it is a function of rugosity and the period of the roughness; and for a capacitance distribution, it is the period of the distribution. Distributions of charge-transfer resistance do not cause time-constant dispersion because they influence neither the ohmic resistance nor the capacitance. As only the high-frequency impedance is affected by roughness and capacity distributions and charge-transfer resistance distributions do not cause frequency dispersion, surface heterogeneity in the form of roughness, capacitance, or charge-transfer resistance cannot provide an explanation for CPE behavior associated with surface distributions.