Automobile exhaust catalysis at the atomic scale: Atom-probe investigations on platinum alloys

P. A J Bagot; A. Cerezo; G. D W Smith; T. Visart De Bocarmé; T. J. Godfrey

doi:10.1002/sia.2484

Automobile exhaust catalysis at the atomic scale: Atom-probe investigations on platinum alloys

P. A J Bagot, A. Cerezo, G. D W Smith, T. Visart De Bocarmé, T. J. Godfrey

School of Engineering & Physical Sciences

Research output: Contribution to journal › Article › peer-review

19 Citations (Scopus)

Abstract

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 (O₂) 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 O₂ 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.

Original language	English
Pages (from-to)	172-177
Number of pages	6
Journal	Surface and Interface Analysis
Volume	39
Issue number	2-3
DOIs	https://doi.org/10.1002/sia.2484
Publication status	Published - Feb 2007

Keywords

Atom-probe
Heterogeneous catalysis
Platinum
Rhodium
Segregation
Surface diffusion

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title = "Automobile exhaust catalysis at the atomic scale: Atom-probe investigations on platinum alloys",

abstract = "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 (O2) 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 O2 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 {\textcopyright} 2007 John Wiley & Sons, Ltd.",

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AU - Cerezo, A.

AU - Smith, G. D W

AU - Visart De Bocarmé, T.

AU - Godfrey, T. J.

PY - 2007/2

Y1 - 2007/2

N2 - 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 (O2) 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 O2 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.

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KW - Atom-probe

KW - Heterogeneous catalysis

KW - Platinum

KW - Rhodium

KW - Segregation

KW - Surface diffusion

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JO - Surface and Interface Analysis

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IS - 2-3

ER -

Automobile exhaust catalysis at the atomic scale: Atom-probe investigations on platinum alloys

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Keywords

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