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

ID: 378932.0, Fritz-Haber-Institut / Theory
Ag-Cu alloy surfaces in an oxidizing environment: A first-principles study
Authors:Piccinin, Simone; Stampfl, Catherine; Scheffler, Matthias
Date of Publication (YYYY-MM-DD):2009-01-11
Title of Journal:Surface Science
Journal Abbrev.:Surf. Sci.
Issue / Number:10-12
Start Page:1467
End Page:1475
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:Recent experiments on model catalysts have shown that Ag-Cu alloys have improved selectivity with respect to pure silver for ethylene epoxidation. In this paper we review our first-principles investigations on the (111) surface of this alloy and present new findings on other low index surfaces. We find that, for every surface orientation, the presence of oxygen leads to copper segregation to the surface. Considering the alloy to be in equilibrium with an oxygen atmosphere and accounting for the effect of temperature and pressure, we compute the surface free energy and study the stability of several surface structures. Investigating the dependence of the surface free energy on the surface composition, we construct the phase diagram of the alloy for every surface orientation. Around the temperature, pressure and composition of interest for practical applications, we find that a limited number of structures can be present, including a thin layer of copper oxide on top of the silver surface and copper-free structures. Different surface orientations show a very similar behavior and in particular a single layer with CuO stoichiometry, significantly distorted when compared to a layer of bulk CuO, has a wide range of stability for all orientations. Our results are consistent with, and help explain, recent experimental measurements.
Comment of the Author/Creator:Special Ertl issue
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: [For a reprint, please contact]
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0811.0864v1.pdf  [460,00 Kb] [Comment:arXiv:0811.0864v1 [cond-mat.mtrl-sci] 6 Nov 2008]  
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