Hydrogen transport through V–Pd alloy membranes: Hydrogen solution, permeation and diffusion

Despite the fastest transcrystalline transport of hydrogen in V, the application of pure V for the membranes permeable to hydrogen is problematic because of too large hydrogen solubility. The latter prevents from working at pressures of practical interest and obtaining a relevant permeation flux. To get a membrane material with optimal hydrogen solubility the substitutional V–Pd alloys with the content of Pd from 5 to 18.8 at% were studied with respect to hydrogen solution, diffusion and permeation in the pressure range from 0.02 to 1.2MPa at 350 and 400°C. Though Pd itself is a good occluder of hydrogen, the alloying of V with Pd suppressed the hydrogen solubility stronger than that is known with any other alloying elements while the hydrogen diffusivity was only slightly reduced. Hydrogen permeability was examined with plane and tubular membranes of the V–Pd alloys with thickness from 60 to 160μm and surface area from 10 to 40cm2. Both sides of the membranes were plated with Pd. Hydrogen permeability of the V–Pd alloys significantly exceeded that of Pd. The permeation flux density reached 0.7scc/(cm2s) at a tolerable concentration of solute hydrogen when feed and permeate pressures of hydrogen were in the range of practical interest: ≈1 and 0.1MPa respectively.