Degradation mechanism of a Pd/Ta composite membrane: catalytic surface fouling with inter-diffusion

Yongha Park, Yeonsu Kwak, Saerom Yu, Arash Badakhsh, Yu Jin Lee, Hyangsoo Jeong, Yongmin Kim, Hyuntae Sohn, Suk Woo Nam, Chang Won Yoon, Jonghee Han, Young Suk Jo*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)

Abstract

Composite metallic membranes comprising Pd coated on group 5 elements such as V, Nb, and Ta are actively explored as a promising material for hydrogen permeable membrane. However, such composite membranes are known to suffer from performance degradations owing to excessive surface fouling due to inter-diffusion between Pd and group 5 elements at high temperatures. In this study, mechanically stable Pd/Ta composite membranes are fabricated, and their H2 permeation flux degradation rates and mechanism of membrane degradation are investigated. Fabricated membranes had full coverage of Pd on Ta surface, with less than 5 wt% of impurities. H2 permeation rates of Pd/Ta membrane samples with different Pd and Ta thicknesses are evaluated at temperatures from 450 °C to 650 °C for a prolonged period of 20–100 h. Over the tested period, degradation in H2 permeation rate was 5% or higher, with temperature being a dominant factor. SEM, TEM, and XRD analyses of the surface and cross-sectional morphology, compositions, and crystallinity reveal that the main degradation mechanism of the composite membrane is the inter-diffusion between Pd and Ta leading to the formation of intermetallic compounds as well as morphology change of the catalytic layer. By evaluating the exponential factor in Sievert's equation over the degradation period, it was found that the diffusion mechanism does not change over time, confirming that the bulk diffusion mechanism is affected by the inter-diffusion. H2 flux degradation was less prominent at lower temperatures with thicker Pd catalytic layers.

Original languageEnglish
Article number157196
Number of pages12
JournalJournal of Alloys and Compounds
Volume854
Early online date28 Sept 2020
DOIs
Publication statusPublished - 15 Feb 2021

Keywords

  • alloying effects
  • composite metallic membrane
  • hydrogen permeable membrane
  • inter-diffusion
  • palladium/tantalum composite
  • permeability degradation

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