Pd–Pt/YSZ composite membranes for hydrogen separation from synthetic water–gas shift streams

Palladium–platinum (Pd–Pt) alloy membranes have been fabricated by sequential, electroless deposition onto porous yttria-stablized zirconia supports manufactured by Praxair, Inc. Membranes were synthesized with thicknesses of 4–12 μm that contained up to 27 wt% Pt. Pd–Pt alloy membranes had lower pure-gas hydrogen flux compared with pure Pd membranes of equal thickness. However, when tested at 673 K under an identical synthetic water–gas shift feed gas mixture composed of H2, H2O, CO2, and CO at 689.5 kPa total pressure, the Pd–Pt alloy membranes had over 25% higher hydrogen fluxes than a pure Pd membrane of similar thickness. Membrane films were analyzed after testing with SEM, EDS, and ICP-AES to corroborate membrane thickness and alloy compositions estimated by mass gain. SEM thickness estimates on membrane cross sections were similar to those estimated by mass gain. ICP-AES analysis was performed on two membranes and confirmed the composition estimated by gravimetric analysis. In five of six membranes the film composition estimated by gravimetric analysis was consistent with the surface composition estimated by EDS which indicated that the membranes had been adequately annealed.

► Pd–Pt alloy membranes were fabricated by sequential, electroless deposition with 5–27 wt% Pt.
► Membranes were annealed at 773 K for 12–30 h to promote metallic interdiffusion and homogeneous Pd–Pt alloy formation.
► Membrane compositions, estimated by mass gain, were verified by ICP-AES.
► Pd–Pt membranes have lower pure-gas hydrogen fluxes than Pd membranes of similar thickness.
► Pd–Pt membranes have higher fluxes than an equivalent Pd membrane in WGS feed gas mixture.