EXPERIMENTAL-STUDY OF THE IMPEDANCE OF BLOCKING QUASI-FRACTAL AND ROUGH ELECTRODES

Impedance measurements on highly ramified and rough electrodes were carried out in quasi-blocking conditions. The responses of both types of electrode exhibit two frequency domains separated by a crossover frequency which depends on the electrode's macroscopic size and is approximately inversely proportional to the electrolyte resistivity. The results show that the length Λ(ω) = (ρ{variant}γω)-1, where ρ{variant} is the electrolyte resistivity and γ the specific capacitance of the interface, is a scaling-length for this problem. It determines the Constant Phase Angle (C.P.A.) behaviour. When Λ(ω) is larger than the size of the electrode the impedance is that of a normal surface. It is shown that scaling implies a power law dependence of the impedance upon the electrolyte resistivity. It also implies that the impedance of such an electrode is a non-extensive quantity. © 1990.