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On the composition of bimetallic near-surface alloys in the presence of oxygen and carbon monoxide

Paper ID Volume ID Publish Year Pages File Format Full-Text
49659 46759 2014 7 PDF Available
Title
On the composition of bimetallic near-surface alloys in the presence of oxygen and carbon monoxide
Abstract

•We studied surface segregation in bimetallic Pt alloys in the presence of oxygen or CO.•Phase diagrams of PtRu alloys as a function of (O2, CO) pressure and temperature•In an oxygen atmosphere, surface becomes rich in more oxophilic metal.•CO provides a weaker driving force than oxygen for adsorbate-induced segregation.

Periodic, self-consistent density functional theory calculations (GGA-PW91) are used to examine surface segregation in close-packed bimetallic Pt-overlayer alloy surfaces (Pt*/M, M = Au, Ag, Cu, Pd, Ir, Rh, Os, Ru, and Re) in different environments. In particular, we find that the thermodynamically stable surface termination in these Pt*/M alloys can be inverted from Pt-terminated in vacuum to M-terminated under exposure to oxygen (for an M that is more oxophilic than Pt). Interestingly, in many of these alloys, Pt is not driven into the bulk; rather it remains in the first subsurface layer where it enhances oxygen binding through a ligand interaction with the surface metal atoms. On the other hand, exposure to CO provides a much milder driving force for the surface composition inversion. To quantify segregation under catalytically relevant conditions, we constructed approximate phase diagrams for the PtRu system as a function of O2 and CO chemical potential (temperature, pressure). The results show that the surface termination inverts with many orders of magnitude higher CO pressure than with O2.

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Keywords
Platinum alloys; Surface segregation; Density functional theory; Catalysis; Oxygen; CO
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On the composition of bimetallic near-surface alloys in the presence of oxygen and carbon monoxide
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Publisher
Database: Elsevier - ScienceDirect
Journal: Catalysis Communications - Volume 52, 5 July 2014, Pages 65–71
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
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Price was $35.95
You save - $31
Price after discount Only $4.95
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