ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY ST UDY OF RESTRICTED DIFFUSIONIN A BILAYER - APPLICATION TO THE HYDROGEN INTERCALATION IN PD PD ALLOY BILAYERS/

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