Defect‐free palladium membranes on porous stainless‐steel support

Defect‐free Pd membranes were prepared by an electroless plating technique on porous stainless‐steel tubes. The effective surface of Pd membranes was up to 75 cm 2 . The helium flux was not detected at room temperature and pressure difference of 3 atm. At 350°C hydrogen permeances of up to {article}{empty}{document}8\ m³ /(m² · h · atm0.5){document} were obtained. A t a pressure difference of 1 atm and 350°C, selectivity coefficients as high as J(H 2 /JN 2 ) = 5,000 were observed. Fluxes of gases, impermeable through the Pd, were quantitatively described as a combination of Knudsen diffusion and viscous flow through the gaps created in the Pd layer at high temperatures. The stability of the prepared membranes at temperatures up to 700°C was investigated. The membranes were stable at 350°C over a period of 1,100 h, with no significant changes in the steady‐state hydrogen flux and with a recrystallization texture and aggregation of Pd grains.