Hydrogen permeability and stability of palladium films in a high pressure reactor

Abstract

Palladium (Pd) thin films were fabricated by colloidal spray deposition (CSD) on substrates of porous yttrium-stabilized zirconium oxide (YSZ). The films were sintered at 1140–1160 °C for 2–3 h in argon and had thickness of 5–11 µm. The hydrogen (H2) permeation flux for the Pd film was measured with simulated feed gases (90% H2/He, syn-gas/steam, or syn-gas/steam with H2S) flowing on the film side and sweep gas (Ar) flowing on the substrate side. The hydrogen flux with the Pd film was obtained by adjusting the flow rate and pressure of the gas. Hydrogen flux values of 121–173 cm3 min−1 cm−2 were measured at 388–596 °C (feed: 90% H2/He at 200 mL min−1; sweep: Ar at 1400 mL min−1; and ΔP = ~170 psi), and the permeability was calculated and compared with literature values. Because Pd is known to be sensitive to some gases, the stability of Pd films was evaluated by examining the microstructures of samples after their exposure to gas mixtures containing CO, CO2, H2O, and H2S. From the results of stability tests in H2S-containing atmospheres, the Pd/Pd4S phase boundary was determined, and this measured boundary was compared to the Pd/Pd4S boundary calculated from the thermodynamic data in the literature.