Composite Pd–Ag membranes supported on modified porous stainless steel substrates were prepared by sequential electroless plating. To improve the stability of the Pd–Ag alloy, two different intermediate layers of α-Fe2O3 and γ-Al2O3 oxides were employed as diffusion barriers. A new activation method was also investigated which consisted in the impregnation of a layer of Pd supported γ-Al2O3 to generate Pd seeds. The membranes were studied by X-ray diffraction, Auger depth profiling, scanning electron microscopy and EPMA. They were tested in a gas permeation system to determine the H permeability and selectivity. The Pd–Ag/PSS membranes had a good thermal resistance. The membranes prepared with alumina diffusion barriers exhibited lower ideal selectivity than the Pd–Ag/α-Fe2O3/PSS. However, the former membranes had two times higher H permeability. The Auger depth profiles did not show the presence of Fe in the Pd–Ag film, indicating that the γ-Al2O3 layer effectively blocked intermetallic diffusion.

Different Oxides Used as Diffusion Barriers in Composite Hydrogen Permeable Membranes. D.Yepes, L.M.Cornaglia, S.Irusta, E.A.Lombardo: Journal of Membrane Science, 2006, 274[1-2], 92-101