Carbon monoxide-induced adatom sintering in a Pd-Fe sub(3)O sub(4) model catalyst

The coarsening of catalytically active metal clusters is often accelerated by the presence of gases, but the role played by gas molecules is difficult to ascertain and varies from system to system. We use scanning tunnelling microscopy to follow the CO-induced coalescence of Pd adatoms supported on...

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Bibliographic Details
Published in:Nature materials 2013-08, Vol.12 (8), p.724-728
Main Authors: Parkinson, Gareth S, Novotny, Zbynek, Argentero, Giacomo, Schmid, Michael, Pavelec, Jiri, Kosak, Rukan, Blaha, Peter, Diebold, Ulrike
Format: Article
Language:English
Subjects:
Carbon
Clusters
Coalescence
Coalescing
Coarsening
Density
Palladium
Scanning tunneling microscopy
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Summary:The coarsening of catalytically active metal clusters is often accelerated by the presence of gases, but the role played by gas molecules is difficult to ascertain and varies from system to system. We use scanning tunnelling microscopy to follow the CO-induced coalescence of Pd adatoms supported on the Fe sub(3)O sub(4)(001) surface at room temperature, and find Pd-carbonyl species to be responsible for mobility in this system. Once these reach a critical density, clusters nucleate; subsequent coarsening occurs through cluster diffusion and coalescence. Whereas CO induces the mobility in the Pd/Fe sub(3)O sub(4) system, surface hydroxyls have the opposite effect. Pd atoms transported to surface OH groups are no longer susceptible to carbonyl formation and remain isolated. Following the evolution from well-dispersed metal adatoms into clusters, atom-by-atom, allows identification of the key processes that underlie gas-induced mass transport.
ISSN:1476-1122
DOI:10.1038/nmat3667