On the Composition of Bimetallic Near-Surface Alloys in the Presence of Oxygen and Carbon Monoxide

Journal Article · Sat Jul 05 00:00:00 EDT 2014 · Catalysis Communications, 52:65-71

DOI:https://doi.org/10.1016/j.catcom.2013.10.021· OSTI ID:1222118

Herron, Jeffrey A.; Mavrikakis, Manos

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 oxophillic 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.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1222118
• Journal Information: Catalysis Communications, 52:65-71, Journal Name: Catalysis Communications, 52:65-71
• Country of Publication: United States
• Language: English

Related Subjects

Environmental Molecular Sciences Laboratory