Effect of overlayer composition on hydrogen permeation of Pd–Cu alloy coated V–15Ni composite membrane

Effect of Cu content (0–60 wt.%) on the hydrogen permeation of Pd–Cu coated V–15Ni composite membranes was investigated in the temperature range of 423–673 K. The hydrogen permeability of composite membrane is closely related to the overlayer composition, it increases with the Cu content until 40 wt.% Cu, and then decreases rapidly with Cu content increasing. The highest hydrogen permeability was obtained for the Pd60Cu40/V–15Ni composite membrane. In the temperature range of 473–673 K, the hydrogen permeability of Pd60Cu40/V–15Ni composite membrane is about 1.5–5.0 times that of Pd60Cu40 alloy membrane. Hydrogen permeation kinetics of the Pd–Cu/V–15Ni composite membranes was mainly limited by bulk diffusion at temperature higher than 473 K. When the temperature is lower than 473 K, the hydrogen permeation flux saturates at high upstream H2 pressure, surface-related reaction should be responsible for the flux saturation at low temperature.