The performance of the NI and the Pd/Au alloy (8 wt%Au) composite membrane prepared by the clectroless and galvanic displacement deposition in a 548 ppm H2S/H-2 mixture was investigated Upon testing, the Pd membrane showed the permeance decline in two stages resulted from the surface site blocking and bulk sulfidanon The Pd membrane also failed to separate H-2 from other gases after the H2S exposure due to the deterioration of the structure caused by the possible formation of bulk Pd4S On the other hand, the Pd/Au alloy membrane exhibited resistance to bulk sulfidation and the permeance decline during the H2S exposure was mainly caused by the surface site blocking by the dissociative adsorption of H2S. which was essentially reversible as evidenced by the near full restoration of the H-2 permeance in pule H-2 at 500 degrees C No significant change in He leak after the H2S tests substantiated that there was no significant structural changes of the Pd/Au alloy membrane due to the bulk sulfide formation Higher temperatures resulted in less permeance loss during poisoning and more permeance restoration during recovery, which was due to the exothermic nature of the dissociative adsorption of H2S on metals (C) 2010 Elsevier B V All rights reserved