Novel ultra-thin Pd and Pd alloy (Pd-Ag, Pd -Cu) membranes, with a phosphorus component, were prepared on a porous hollow fiber alpha-alumina support. The aim was to study the effect of the presence of a P additive on the behavior of the membranes towards sulfur poisoning. To incorporate P in the structure, the membranes were exposed to PH3 as a gaseous phosphorous source. The performance and sulfur resistance of the membranes with and without P was evaluated by measuring the hydrogen permeance and the H-2/N-2 selectivity at 673 K before and during exposure to a gas mixture of 100 ppm H2S in H-2, and also after regeneration in H-2. The membranes were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), both before exposure to H2S and after exposure/regeneration. XRD shows no detectable amounts of sulfur or phosphorus compounds in any of the exposed or P-treated membranes respectively. XPS indicates that S was located On the surface of the H-2/N-2 treated Pd and Pd-Ag membranes. No S was detected On the surface of the Pd-Cu membranes indicating that no irreversible S compounds were formed in the latter. P was also detected on the surface of the P-treated membranes. The presence of phosphorus lowered the hydrogen permeance and H-2/N-2 selectivity; however it drastically improved the Pd-alloy membranes capacity of recovery in H-2 after H2S poisoning. The Pcl-Cu membrane recovered only part of its H-2 permeance after regeneration, going from 11.2 x 10(-7) mol m-2 s(-1) Pa-1 (as-prepared) to 2.3 x 10(-7) mol m(-2) S-1Pa-1, while in the presence of P the H2 permeance varied from 5.2 x 10(-7) mol m(-2) s(-1) Pa-1 (as-prepared) to 6.5 x 10(-7) mol m(-2) s(-1) Pa-1 and its H-2/N-2 selectivity increased from 30,000 to 40,000. Similarly, the Pd-Ag membrane recovered better in the presence of P going from 17 x 10(-7) mol m(-2) s(-1) Pa-1 (asprepared) to 6.3 x 10(-7) mol m(-2) s(-1) Pa-1 in contrast to 52 x 10(-7) mol m(-2) s(-1) Pa-1 (as-prepared) to 5.9 x 10(-7) mol m(-2) s(-1) Pa-1 in the absence of P. SEM images show that in the absence of P. more cracks and pinholes are visible on the surface of the H-2/N-2 exposed membranes. The presence of P produces more homogeneous surfaces and less segregation, conferring a structural integrity to the membrane by suppressing the formation of cracks and pinholes. (C) 2014 Elsevier B.V. All rights reserved,