A transfer function for electrochemical hydrogen permeation through metallic membranes was defined, and its analytical form was obtained from a theoretical model which included surface processes and bulk diffusion. By means of the EIS technique, combined with electrochemical hydrogen permeation, this transfer function was experimentally measured for iron membranes, covered with a thin layer of electrodeposited Pd at the exit side, immersed in both acid and alkaline media at the input cell. By fitting the model to experimental results, a hydrogen diffusion coefficient in iron of 9.6 x 10-9m2/s was obtained; independently of both the membrane thickness and the input side solution pH. It was demonstrated that the oxide film formed on iron at the output side of the membrane delayed hydrogen transport, and that the thin Pd layer avoided the formation of this film without introducing significant new delays.

Hydrogen Diffusion in α-Iron Studied using an Electrochemical Permeation Transfer Function. P.Bruzzoni, R.M.Carranza, J.R.Collet-Lacoste, E.A.Crespo:

Electrochimica Acta, 1999, 44[16], 2693-704