Hydrogen permeation performance of three thin palladium- copper composite membranes with different thicknesses had been studied between 398 K and 753 K. Hydrogen permeance was obtained up to 2.7 x 10(-6) mol/(m(2) s Pa) with an ideal selectivity over 1000 at 753 K. The hydrogen permeation exhibited two different activation energies over the temperature range: lower activation energy of about 9.8 kJ/mol above 548 K, while higher activation energy of about 26.4 U/mol below 548 K. After permeation tests, the alloy membranes were characterized by X-ray photoelectron spectroscopy, scanning electron microscopy, energy dispersive X-ray analysis and in situ X-ray diffraction. Palladium segregation on the surface of these palladium-copper alloys may induce changes of hydrogen permeation performance and thus influence the activation energies. (C) 2007 Elsevier B.V. All rights reserved.