Hydrogen transport by group 5 metals: Achieving the maximal flux density through a vanadium membrane

Hydrogen transport by 100-$\mu$m-thick vanadium and palladium membranes was studied in the pressure range from 1 $\times$ 10$^{-8}$ to 4.5 $\times$ 10$^{-1}$ MPa at a temperature of 400$^\circ$C. Both sides of the vanadium membrane were covered by 2 $\mu$m of palladium (Pd–V–Pd) for facilitating the dissociative absorption and associative desorption of H$_2$ molecules. At low pressures, hydrogen flux densities through vanadium and palladium membranes are nearly the same; at high pressures, the flux through the vanadium membrane becomes 16 times larger than the flux through the palladium membrane and attains a value of 2.4 scc cm$^{-2}$ s$^{-1}$. This flux of permeating hydrogen is larger than all values ever observed earlier for membranes made of group 5 metals or any other unsupported metal membranes.