Electrochemical Impedance Spectroscopy and its Applications by Andrzej Lasia

Author:Andrzej Lasia
Language: eng
Format: epub, pdf
Publisher: Springer New York, New York, NY

The porous electrode model described in Eq. (9.7) cannot be represented by a simple connection of R, L, and C elements. However, it can be represented by a semi-infinite series of R-C elements called a transmission line [410, 411], shown in Fig. 9.4. Of course, this representation is equivalent to Eq. (9.7). Some authors tried to use a transmission line to approximate experimental data using a sufficient number of RC elements and verifying whether the number of these parameters was sufficient. This procedure can approximate, then, experimental impedances, but the use of Eq. (9.7) is more appropriate because it allows for the direct estimation of certain parameters and their standard deviations. This model is included in the recent version of the ZView program.

The model presented above is valid for the isolated pore. However, such pores are usually present in an electrode material, and the capacitance of the top flat layer must be taken into account and added to the total electrode impedance [352]. In such a case the total impedance consists of the impedance of the porous part, , and that of a flat part of the electrode, . The corresponding electrical equivalent circuit is displayed in Fig. 9.6.

Fig. 9.6Equivalent electrical circuit of electrode containing porous and external flat part

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