Preparation of hydrogen-permselective palladium-silver alloy composite membranes by electroless co-deposition

This study investigates the co-deposition behavior of palladium and silver on porous alumina by means of electroless plating technique. The fabrication parameters of the membranes in electroless plating process for the preparation of Pd-Ag composite membrane are also investigated. The thickness and surface morphology of the specimen is also inspected using a scanning electron microscope (SEM). For the Pd-90-Ag-10/alpha-alumina composite membrane prepared at 333 K, the thickness of the Pd-Ag layer on the alpha-Al2O3 support for plating 8 h is 20 mum. Subsequently, the Pd90Ag10/alpha-alumina composite membrane (20 mum) is used for hydrogen and nitrogen permeation experiments under 473-616 K and 80-250 kPa. The ideal separation factor of H-2/N-2 through the membrane is found in the range 30-178 under the indicated experimental conditions. Furthermore, a resistance model is used to account for the simultaneous transport of hydrogen through the a-alumina support and skin layer of the Pd-90-Ag-10/alpha-alumina composite membrane. It reveals that the transport behavior of hydrogen through the skin layer of the membrane is a combination of solution-diffusion and Knudsen diffusion with minimal contribution of viscous flow. (C) 2003 Elsevier Science B.V. All rights reserved.