Double or Triple Pore Structure

4 Porous Electrode with Ohmic Drop in Solution and in Electrode Material (i c = 0,rg 0, r. / 0) 

Earlier it was assumed that the electrode material was well conducting and its resistance negligible. However, when the resistivity of the electrode material cannot be neglected, i.e., it becomes comparable to or larger than that of the solution, a 

Assuming that the electrode impedance does not depend on the position in a pore (macrohomogeneous material), an analytical equation describing this circuit was developed [426 29]  

Equation (9.16) can also be written in a form similar to that in Eq (9 7)- 

Equation (9.19) differs from de Levie s equation, Eq. (9.7), by the presence of one additional term. It should be noted that when r = 0, Eq. (9.19) reduces to Eq. (9.6) or (9.7). When the frequency m oo, A - oo, the second term in Eq. (9.19) goes to zero and the first term becomes Wa,p, which corresponds to the average harmonic resistance of the solution and the electrode. When w 0, the real part of the first term in parentheses goes to 2/3 and the first term becomes 2/ n,p/3, while the real part of the second term goes to R o,p/3. This means that the low-frequency impedance is real and equal to 2R o,p/3 + R o,p/3. At low frequencies the imaginary parts of both terms go to infinity and the electrode displays its capacitive behavior. The complex plane plots of the total impedance, as well as those of the first and second terms, are compared in Fig. 9.15. The second term in Eq. (9.19), Fig. 9.15c, shows a complex plane plot that is similar to that in the absence of the electrode resistance (de Levie s solution). The first term shows a 

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