To enable the formation of defect-free PdAu composites by electroless plating, the vacuum-assisted ZrO2-modified method was optimized on top of porous stainless steel disks. Both the ZrO2-modified supports and the PdAu synthesized membranes were characterized by XRD (X-ray diffraction), SEM (scanning electron microscopy), EDS (energy dispersive X-ray analysis) and XPS (X-ray photoelectron spectroscopy). SEM cross-section results showed that dense, continuous, defect-free PdAu films were deposited on top of the ZrO2-modified PSS disks, and the EDS data indicated that no significant concentration gradient was present on the thickness. At 400 degrees C and 100 kPa, the pure hydrogen permeation flux for a 10 mu m thick PdAu membrane was about 0.14 mol s(-1) m(-2) and the H-2/N-2 ideal selectivity was higher than 10,000. (C) 2012 Elsevier B.V. All rights reserved.