Effect of metal-support interface on hydrogen permeation through palladium membranes

Thin palladium membranes of different thicknesses were prepared on sol-gel derived mesoporous γ-aluminai α-alumina and yttria-stabilized zirconial a-alumina supports by a method combining sputter deposition and electroless plating. The effect of metalsupport interface on hydrogen transport permeation properties was investigated by comparing hydrogen permeation data for these membranes measured under different conditions. Hydrogen permeation fluxes for the Pdlγ-Al ₂O ₃/-al ₂O ₃ membranes are significantly smaller than those for the Pd/YSZ/α.-Al ₂O ₃ membranes under similar conditions. As the palladium, membrane thickness increases, the difference in permeation fluxes between these two groups of membranes decreases and the pressure exponent for permeation flux approaches 0.5 from 1. Analysis of the permeation data with a permeation model shows that both groups of membranes have similar hydrogen permeability for bulk diffusion, but the Pd/γ-Al ₂O ₃/a-Al ₂O ₃ membranes exhibit a much lower surface reaction rate constant with higher activation energy, due possibly to the formation of Pd-AI alloy, than the Pd/YSZ/α-Al ₂O ₃ membranes.