DISSERTATION
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Results and Discussion<br />
C d = 1<br />
(3.4)<br />
2πfZ<br />
′′<br />
where ω is the angular frequency.<br />
Figure 3.13. Example of a Nyquist plot used for the system characterization and<br />
calculation of Cd. The presented curve was recorded for a potential of 0.8 V vs. Pb/PbF2/5<br />
M KF (0.2 V vs. Ag/AgCl/3 M KCl) in the frequency range from 4 kHz to 100 Hz. The<br />
measurement was performed in 10 mM PB with 20 mM K2SO4. A capacitive bridge (2 µF)<br />
was used. The beige line represents the fit to the RC equivalent circuit.<br />
Figure 3.14 shows the obtained Cd values for three electrolyte solutions of different ionic<br />
strengths calculated at three different frequencies. Comparing different ionic strengths, no clear<br />
minimum is observed (Figure 3.14, a-c). On the contrary, for the highest ionic strength a<br />
maximum was observed in one part of the curve. This behavior was previously observed for<br />
high ionic strength electrolytes 83 . Furthermore, looking at the individual ionic strength, the<br />
same trend can be observed for all three chosen frequencies. However, when different ionic<br />
strengths for the same frequency are compared (Figure 3.14, d-f), the biggest difference is<br />
observed between different ionic strengths for a frequency of 100 Hz (Figure 3.14, d).<br />
3.2 Importance of knowing the surface 45