Preparation of thin and highly stable Pd/Ag composite membranes and simulative analysis of transfer resistance for hydrogen separation

Composite Pd/Ag membranes supported on an α-alumina substrate have been prepared by sequential electroless plating and the morphology of the membranes has been examined by SEM and XRD analysis. SEM pictures revealed that the Pd/Ag film was of columnar form perpendicular to the substrate. Homogeneous alloy films of Pd/Ag were obtained by annealing the separate Pd and Ag deposited layers at temperatures higher than 600 °C in a hydrogen atmosphere. Hydrogen fluxes of up to 0.35 mol/(m2 s) and hydrogen/nitrogen selectivities of 4500 were obtained and a long-term temperature cycling test showed no deterioration in membrane performance. A simulative analysis was carried out to investigate the effect of boundary layer and the distribution of hydrogen transfer resistance between the boundary layer, the Pd/Ag film and the substrate.