Improvement in the electrochemical pulse time-lag technique made it possible to measure the hydrogen diffusion coefficient on the silver-rich side of Pd-Ag alloys, in spite of the extremely low hydrogen solubility in pure silver and silver-rich alloys. The measured macroscopic diffusion coefficient of hydrogen in Ag attained values comparable to diffusion in pure Pd, but was orders of magnitude higher than that in the Pd0.5Ag0.5 alloy. The diffusion coefficient reached values of about 8 x 10-8cm2/s for Pd0.2Ag0.8 and 6 x 10-8cm2/s for pure silver. The calculated mean-square distance exhibited an analogous behavior, with increasing silver content, to that of the measured macroscopic diffusion coefficient. This implied that hydrogen diffusion through Pd-Ag alloys took place preferably by a roundabout route via so-called Pd-rich diffusion paths; avoiding Ag-rich regions.

Hydrogen-Diffusion in Pd1−xAgx (0⩽x⩽1). L.Opara, B.Klein, H.Züchner: Journal of Alloys and Compounds, 1997, 253–254, 378-80