The results were presented of low-temperature H permeation experiments performed by using a Pd/Cu membrane. The inlet pressure was varied from 5 to 180psig, at 25 to 275C. The Pd/Cu membranes exhibited flow stability problems at low temperatures and pressures when using ultra-high purity H. A pre-conditioning step of high temperatures and inlet pressures of pure H was necessary in order to stimulate any substantial permeation flow. After pre-conditioning, the results revealed zero H flow when using 3 to 4%H, mixed with He or Ar. It was suggested that the inert gas atoms were adsorbed into the membrane surface and thus blocked H-atom dissolution. When using pure H at low to moderate temperatures and low pressures, no measurable permeation flow was observed. Also, zero permeation flow was observed at a relatively high temperature (150C) and a low inlet pressure (5psig). The cause of the zero permeation flow, when using pure H, was attributed to interface control of the permeation process. Such interface control could be due to an insufficient energy to split the H molecule into H atoms, or to a reversible phase change - from β to α - of crystals at the near surface.

Low Temperature Hydrogen Transport using a Palladium/Copper Membrane. P.A.Lessing, H.C.Wood, L.D.Zuck: Journal of Materials Science, 2003, 38[11], 2401-8