The effect of electroless plating time on the morphology, alloy formation and H_2 transport properties of Pd-Ag composite membranes

摘要

The effect of plating times and metal deposition sequence on the morphology of Pd-Ag films on porous supports and also on alloy formation has been investigated. Pd-Ag composite membranes were prepared by electroless plating; the substrates were modified using dip coated alumina and in situ hydrothermal synthesis of NaA zeolite with secondary growth. The chemical and physical phenomena involved in the atomic diffusion during the thermal treatment as well as the crystalline structure were tracked by scanning electron microscopy, energy-dispersive X-ray analysis, X-ray photoelectron spectroscopy, and X-ray diffraction. In order to isolate the main component of the hydrogen transport (solution-diffusion mechanism), the composite membranes were considered as layers in series, with porous and dense parts; the porous areas were modeled by the dusty gas model. This allowed a more accurate estimation of Sievert's transport parameters and a critical comparison with data reported in the literature.