Fig. 5.
The impedance of electrochemical electrodes fabricated from a number of materials is well described by a constant-phase-element model. The real (circles, left axis) and imaginary (triangles, right axis) admittances are plotted versus frequency for Au, DLC:N and ITO planar electrodes with mean areas of 365, 384 and 285 μm2, respectively, whereas the CF microelectrodes had a mean area of 69 μm2 (areas estimated from capacitance measurements). The admittances represent average values from seven (DLC:N), six (Au) or five (ITO and CF) electrodes. The fits to the CPE model are the solid curve (real admittance) and dashed curve (imaginary admittance). Since fits were not very sensitive to Rs, Rs was set to a value of zero. The “background” admittance with electrodes covered with insulation was subtracted in each case.