Preparation and characterization of Pd-Cu alloy composite membranes

Thin Pd-Cu/ZrO₂-PSS composite membranes were prepared by modified electroless plating technique on 0.2 μm graded 316L porous stainless steel (PSS) disks. After the surface of PSS was modified by Pd-doped zirconia, the zirconia side of the modified support was successively coated with palladium and copper by electroless plating. Finally, the as-deposited Pd-Cu/ZrO₂-PSS composite membrane was annealed in hydrogen at 773 K for 5-10 h in order to form a homogeneous palladium-copper alloy film by thermal diffusion. XPS analyses showed the average surface composition of the two membranes were respectively Pd₉₀Cu₁₀ and Pd₅₉Cu₄₁ (mass fraction/%). XRD analyses indicated that deposited Pd₉₀Cu₁₀ alloy film contained only fcc (face-centred cubic) phase structure whereas Pd₅₉Cu₄₁ alloy film contained a mixture of fcc and bcc (body-centred cubic phase). Surface micrographs made by SEM showed the presence of some visible pin-holes on the 5 μm thick Pd-Cu/ ZrO₂-PSS membrane, and pinhole free surface for the 10 μm one which should possess an excellent perm-selectivity for hydrogen.