Mechanism of grain reconstruction of Pd and Pd/Ni wires during Pt–catchment

Asbjørn Slagtern Fjellvåg*, Peter Stanley Jørgensen, David Waller, David Stephen Wragg, Marco Di Michiel, Anja Olafsen Sjåstad*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review


We have investigated industrial Pd and Pd/Ni (91.3/8.7 at.%) wires and gauzes used for Pt-catchment during the ammonia oxidation process, focusing on the origin of the grain reconstruction phenomena. In situ X-ray absorption tomography experiments reveal severe reconstruction of polycrystalline Pd and Pd/Ni wires over the course of 10 days, caused solely by the presence of gaseous PtO2 and dry air. A high partial pressure of PtO2 results in higher Pt-catchment rates, which in turn causes more severe reconstruction of the Pd-based wire. Additionally, the Pt-catchment efficiency is reduced when the Pt-content on the wire surface increases. Scanning electron microscopy accompanied by energy dispersive X-ray analysis reveal that Pt diffuses rapidly into the wire core via grain boundaries already after 1 day of Pt catchment. However, quasi monocrystalline (pre-annealed) Pd and Pd/Ni samples show significantly less Pt-catchment and only a little reconstruction compared to the polycrystalline samples. With support from experiments and simulations, we conclude that bulk diffusion is one of the main limitations for Pt-catchment on both poly- and quasi monocrystalline Pd and Pd/Ni wires. The diffusion limitation causes a high surface concentration of Pt, which in turn limits further Pt-catchment due to a gas-surface equilibrium. The polycrystalline wire can overcome the diffusion limitation by utilizing a rapid grain boundary diffusion, transporting both Pt to the wire core and Pd to the wire surface. However, this transport process is also the cause of grain reconstruction.
Original languageEnglish
Article number101359
Number of pages16
Publication statusPublished - 2022


Dive into the research topics of 'Mechanism of grain reconstruction of Pd and Pd/Ni wires during Pt–catchment'. Together they form a unique fingerprint.

Cite this