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Automobile exhaust catalysis at the atomic scale: atom‐probe investigations on platinum alloys
Author(s) -
Bagot P. A. J.,
Cerezo A.,
Smith G. D. W.,
de Bocarmé T. Visart,
Godfrey T. J.
Publication year - 2007
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.2484
Subject(s) - catalysis , rhodium , platinum , chemistry , alloy , oxide , atomic units , atom probe , atom (system on chip) , analytical chemistry (journal) , organic chemistry , physics , quantum mechanics , computer science , embedded system
A dedicated three‐dimensional atom‐probe has been fitted with an in situ high pressure/temperature reaction cell. This was used for studying the interaction of gases with Pt‐alloy surfaces typical of those employed in automotive exhaust catalysis. The reactions of nitric oxide (NO) and oxygen (O 2 ) on Pt and Pt–17.4 at.% Rh FIM specimens were explored, revealing a range of surface restructuring and segregation effects, which depend sensitively on catalyst composition, orientation, temperature and gas chemistry. Specifically, we observed that exposure of Pt–Rh to either NO or O 2 at 422–473 K and 10 mbar induced Rh surface segregation uniformly over the surface. However, on raising the temperature to 573 K or higher, the Pt–Rh{111} surface remained Rh‐enriched but the Pt–Rh{001} surface became severely Rh‐depleted. We attribute this observation to the possible diffusion of Rh species across the specimen apex, indicating that segregation occurs in directions both normal and parallel to the surface in Pt–Rh catalysts. Copyright © 2007 John Wiley & Sons, Ltd.