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Pd–Cu composite membranes were made by successive electroless deposition of Pd and then Cu onto various tubular porous ceramic supports. Pure gas (H2, N2) permeability tests were conducted at high temperature with simultaneous annealing to induce intermetallic diffusion. Both the alloy composition and the support structure are shown to be responsible for the differences in membrane performance. The highest hydrogen permeability was observed at an alloy composition of 60 wt.% Pd at a constant temperature of 350°C. A typical H2 flux for this membrane was 0.81 mol/m2@s at 350°C and 255 kPa H2 partial pressure.

We studied the effect of Pd alloy composition and substrate characteristics on the H2 permeation of composite membranes. Regarding the dependence of hydrogen permeability on the metal film composition, we found that it was consistent with the behavior noticed by McKinley and described elsewhere in the literature. The highest hydrogen permeability was observed at an alloy composition of 60 wt.% Pd at a constant temperature of 350°C. Support structure also was found to affect significantly the H2 permeation of these membranes. The top layer pore size and roughness were found to determine the minimum metal film thickness to form an impervious membrane. Nominally 1-µm-thick metal films were consistently deposited on top of 20 nm and 50 nm cut-off ceramic supports by a sequential electroless plating technique. Additionally, the support’s internal structure affects the overall mass transfer resistance to H2 permeation as much higher H2 fluxes were observed for similar metal films on asymmetric supports compared to filters with a symmetric structure.