Hydrogen permeability and sulfur tolerance of a novel dual membrane of PdAg/PdCu layers deposited on porous stainless steel

Palladium membrane is the best choice for hydrogen ultra-purification; however, it suffers from difficulties such as hydrogen embrittlement and poisoning with sulfur compounds. In order to overcome these problems, a dense PdAg alloy composite membrane was synthesized using the sequential electroless plating of Pd and Ag onto a porous stainless steel. Then a thin layer of sulfur tolerant PdCu fcc phase was deposited on this layer by electroless plating, too. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) were used to study lattice phase, alloying, thickness and elemental composition of the membrane. The membraneʹs permeation performance was tested at different temperatures between 502 and 553 K and a pressure difference up to 90 kPa. By lowering the temperature from 553 K to 502 K, the best pressure exponent changes from 0.5 to 0.7. Hydrogen permeability of 1.77×10−8 mol m/m2 s Pa0.5 has been obtained at a temperature of 553 K. The membrane sulfur resistance was confirmed by exposure to a combined gas of H2 and H2S.