Optimization and characterization of electroless co-deposited PdRu membranes: Effect of the plating variables on morphology

PdRu films were successfully synthesized on top of non-porous stainless steel supports by electroless co-deposition. The effect of synthesis variables on morphology, substrate adherence, bulk and surface composition was studied. The microstructure and morphology of the samples were analyzed by X-ray diffraction and scanning electron microscopy. Homogeneous and defect-free PdRu films were obtained employing baths at low pH, moderate to high agitation speeds, high concentration of hydrazine, using EDTA as a stabilizer and temperatures near 50 °C. Films characterized by X-ray photoelectron spectroscopy showed Pd segregation after annealing the sample at 400 °C in H2 (5%)/Ar in the load-lock chamber of the spectrometer. The optimized conditions were employed to synthesize a PdRu composite membrane on top of a tubular porous stainless steel substrate (0.1 μm grade). Hydrogen permeation was measured over a 350–450 °C temperature range and a trans-membrane pressure up to 100 kPa. The PdRu membrane showed good performance with a hydrogen permeability of 6.5 × 10−9 mol m−1 s−1 Pa−0.5 and a selectivity higher than 1700.

► PdRu membranes were prepared by simultaneous electroless plating technique. ► The films synthesized in an EDTA-free plating bath presented heterogeneous and dendritic morphologies. ► Defect-free PdRu films were synthesized employing baths at pH 11.5, using EDTA as a stabilizer and temperatures near 50 °C. ► Pd segregation to the surface takes place under hydrogen permeation experiments.