Electrochemical impedance of mercury electrodes with hematite particles adhered

The effect of hematite particles adhesion on the electrochemical impedance of mercury electrodes was studied at different electrode potentials. The im pedance decreases as the number of attached particles increases: this imped ance decrease is related to strong adhesion of particles. The impedance dia grams show, in the low frequency range, the presence of a constant phase el ement (CPE), with an exponent of ca. 0.5. The experimental results are anal yzed in terms of an equivalent circuit including the CPE. The magnitude of this CPE is directly related to the coverage of the electrode. A qualitativ e interpretation for this behavior, when an AC signal is applied. is propos ed in terms of a pore model for the metal/hematite particles interphase.