Hydrogen permeation of Pd–Ag alloy coated V–15Ni composite membrane: effects of overlayer composition

Effects of Ag concentration (0–45 at.%) on the hydrogen permeation of Pd–Ag coated V–15Ni composite membranes were investigated in the temperature range of 423–673 K, using gas permeation technique. Dense and uniform Pd–Ag alloy overlayer was obtained using a DC multi-target sputtering system. At temperatures higher than 473 K, the hydrogen permeation through the V–15Ni/Pd–Ag composite membranes was mainly bulk-diffusion limited and had little dependence on the overlayer composition. At 473 K and lower, the addition of Ag to the overlayer obviously increased the hydrogen permeability of the V–15Ni/Pd–Ag composite membranes. The hydrogen permeability of Pd–30Ag coated composite membrane was 2.53×10−8 mol H2 m−1 s−1 Pa−1/2 at 473 K, which was about 27% higher than that of Pd-coated composite membrane. The resistance of overlayer to hydrogen-induced cracking increased with the addition of Ag. Effects of the interfacial contaminants on the hydrogen permeation of the composite membrane were discussed.