DISSERTATION

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Results and Discussion
where σm represents the excess charge of the metal and Cd the differential capacitance. This
equation explains that at the pzc the Cd-E curve shows a minimum. In order to find this potential,
we need to evaluate the nature of the differential capacitance and on what parameters it depends.
surface at the potential of zero (free)
charge
σ m = 0
σ i = 0
σ ddl = 0
surface at the potential of zero total
charge
σ m + σ i = 0
σ ddl = 0
surface at any other potential
σ m + σ i + σ ddl = 0
Figure 3.11. Schematic representation of the electrode-electrolyte interface upon
polarization at different potentials. σm, σi and σddl stand for the excess charge in the metal,
compact layer and diffuse double layer, respectively.
3.2 Importance of knowing the surface 42