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          Institute: Fritz-Haber-Institut     Collection: Theory     Display Documents

ID: 360596.0, Fritz-Haber-Institut / Theory
First-principles investigation of Ag-Cu alloy surfaces in an oxidizing environment
Authors:Piccinin, Simone; Stampfl, Catherine; Scheffler, Matthias
Date of Publication (YYYY-MM-DD):2008-02-26
Title of Journal:Physical Review B
Journal Abbrev.:Phys. Rev. B
Issue / Number:7
Start Page:075426-1
End Page:075426-9
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:In this paper, we investigate by means of first-principles density functional theory calculations the (111) surface of the Ag-Cu alloy under varying conditions of pressure of the surrounding oxygen atmosphere and temperature. This alloy has been recently proposed as a catalyst with improved selectivity for ethylene epoxidation with respect to pure silver, the catalyst commonly used in industrial applications. Here, we show that the presence of oxygen leads to copper segregation to the surface. Considering the surface free energy as a function of the surface composition, we construct the convex hull to investigate the stability of various surface structures. By including the dependence of the free surface energy on the oxygen chemical potential, we are able compute the phase diagram of the alloy as a function of temperature, pressure, and surface composition. We find that, at temperature and pressure, typically used in ethylene epoxidation, a number of structures can be present on the surface of the alloy, including clean Ag(111), thin layers of copper oxide, and thick oxidelike structures. These results are consistent with, and help explain, recent experimental results.
External Publication Status:published
Document Type:Article
Communicated by:Matthias Scheffler
External Affiliations:School of Physics, The University of Sydney, Sydney, New South Wales 2006, Australia
Identifiers:URL: [Free to Read]
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