Resistance limiting low-frequency

The limiting (low frequency) resistance / i. is obtained from the intercept of the impedance plot with the real axis as illustrated in Fig. 20.27a. In real-life systems, however, the semicircle is not centered on the real axis (i.e., depressed arc phenomenon) nor is the capacitive branch parallel to the imaginary axis as exemplified in Fig. 20.27b. The microscopic origins of these effects are not very well understood at present but are believed to be related to surface inhomogeneities" and roughness" effects (see above). Other analyses of the impedance of polymer-modified electrodes are available, including effects related to migration within the film and (lateral) redox-site interactions [114,115]. 

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