Different oxides used as diffusion barriers in composite hydrogen permeable membranes

D. YEPES, L.M. CORNAGLIA, S. IRUSTA AND E.A. LOMBARDO

JOURNAL OF MEMBRANE SCIENCE

Elsevier

Año: 2006 vol. 274 p. 92 - 101

0376-7388

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   a-Fe2O3   and g-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 g-Al2O3 to generate palladium seeds.  The  membranes were  studied by  XRD, Auger depth profiling,  SEM and EPMA. They  were tested in a gas permeation system to determine the  hydrogen 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/a-Fe2O3/ PSS. However, the former membranes had two  times higher hydrogen permeability.  The Auger depth profiles did not  show the presence of Fe in the Pd-Ag film, indicating that the g-Al2O3 layer effectively blocked the intermetallic diffusion.