ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY STUDY OF RESTRICTED DIFFUSION IN A BILAYER - APPLICATION TO THE HYDROGEN INTERCALATION IN PD/PD ALLOY BILAYERS

The diffusion of an intercalated species into a two-layers thin film is studied theoretically using Electrochemical Impedance Spectroscopy (EIS). The restricted diffusion impedance expression is given in this paper and some possible shapes of the impedance diagrams are shown in the Nyquist complex plane. The intercalation of hydrogen into palladium / palladium alloy bifilms is taken as a model system and is studied experimentally by EIS. There is a good agreement between impedance measurements and theoretical results. Hydrogen concentration and diffusion coefficient values in the various materials have been determined using a fitting procedure.