par Bagot, Paul A. J.;Cerezo, Alfred;Smith, George D.W.;Visart de Bocarmé, Thierry 
;Godfrey, Terence J.
Référence Surface and interface analysis, 39, 2-3, page (172-177)
Publication Publié, 2007-01-23
;Godfrey, Terence J.Référence Surface and interface analysis, 39, 2-3, page (172-177)
Publication Publié, 2007-01-23
Article révisé par les pairs
| Résumé : | 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. |
