Identification of thermally stable Pd-alloy composite membranes for high temperature applications

In this work, the inert gas leak evolution problem in electrolessly-plated palladium (Pd)-based composite membranes has been revisited. Pd was doped with a higher melting point element such as ruthenium (Ru) or platinum (Pt) and the thermal stability of the membranes was evaluated. Pd, Pd–Ru and Pd–Pt composite membranes were synthesized by electroless plating techniques and the rate of increase of the nitrogen leak in the temperature range of 773–873 K for these membranes in a pure hydrogen atmosphere was determined. The results showed that doping Pd with Pt or Ru significantly reduces the rate at which the nitrogen leak increased compared to a pure Pd membrane by almost one order of magnitude. The effect of these Pd-alloys on the hydrogen permeance stability at high temperatures (≥823 K) was also investigated. The addition of a trace amount, less than 1 wt%, of Ru to Pd was sufficient to enhance the thermal stability of pure Pd membrane by lowering the nitrogen leak growth rate, though the hydrogen permeance stability was not improved. The Pd–Pt alloy membrane, despite having a lower hydrogen permeance, had a very stable hydrogen permeation flux at higher temperatures (up to 873 K).