title: Unexpected behavior of the surface composition of PtRh alloys during chemical reaction.
abstract: The changes in the surface composition of a Pt(50)Rh(50)(100) alloy due to an ongoing 2H(2) + O(2)-->2H(2)O chemical reaction have been studied in situ. Exploiting the high-energy resolution and surface sensitivity of synchrotron radiation core-level spectroscopy it was possible to monitor the population of the two transitions metals atoms at the gas-surface interface. Sequences of fast high-resolution core-level spectra of the Rh3d(5/2), Pt4f(7/2), and O1s core levels showed a continuous exchange of atoms between the first and subsurface layers. An unexpected Pt surface enrichement was found under slightly oxidizing conditions, opposite to what found in a highly oxidizing atmosphere.
authors.affiliation: Dipartimento di Fisica, Università di Trieste, Via Valerio 2, 34127 Trieste, Italy. alessandro.baraldi@elettra.trieste.it
authors.forename: Alessandro
authors.initials: A
authors.lastname: Baraldi
authors.forename: Dario
authors.initials: D
authors.lastname: Giacomello
authors.forename: Luca
authors.initials: L
authors.lastname: Rumiz
authors.forename: Mauro
authors.initials: M
authors.lastname: Moretuzzo
authors.forename: Silvano
authors.initials: S
authors.lastname: Lizzit
authors.forename: Francesco
authors.initials: F
authors.lastname: Buatier de Mongeot
authors.forename: Giorgio
authors.initials: G
authors.lastname: Paolucci
authors.forename: Giovanni
authors.initials: G
authors.lastname: Comelli
authors.forename: Renzo
authors.initials: R
authors.lastname: Rosei
authors.forename: Bernard E
authors.initials: BE
authors.lastname: Nieuwenhuys
authors.forename: Ugo
authors.initials: U
authors.lastname: Valbusa
authors.forename: Maya P
authors.initials: MP
authors.lastname: Kiskinova