Ab initio study of element segregation and oxygen adsorption on PtPd and CoCr binary alloy surfaces
| Autor: | Manfred Bobeth, Wolfgang Pompe, Lucio Colombi Ciacchi, Arezoo Dianat, Nicola Seriani, Janina Zimmermann |
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| Přispěvatelé: | Publica |
| Jazyk: | angličtina |
| Rok vydání: | 2008 |
| Předmět: |
alloying
Alloy FOS: Physical sciences Chemisorption chemistry.chemical_element engineering.material Oxygen Electronegativity Adsorption Computational chemistry Materials Chemistry platinum Surface layer Bimetallic strip Condensed Matter - Materials Science Materials Science (cond-mat.mtrl-sci) Cobalt Surfaces and Interfaces palladium Condensed Matter Physics Surface energy Surfaces Coatings and Films electronic structure calculation chemistry engineering Physical chemistry chromium bimetallic surface |
| Popis: | The segregation behavior of the bimetallic alloys PtPd and CoCr in the case of bare surfaces and in the presence of an oxygen ad-layer has been studied by means of first-principles modeling based on density-functional theory (DFT). For both systems, change of the d-band filling due to charge transfer between the alloy components, resulting in a shift of the d-band center of surface atoms compared to the pure components, drives the surface segregation and governs the chemical reactivity of the bimetals. In contrast to previous findings but consistent with analogous PtNi alloy systems, enrichment of Pt atoms in the surface layer and of Pd atoms in the first subsurface layer has been found in Pt-rich PtPd alloy models, despite the lower surface energy of pure Pd compared to pure Pt. Similarly, Co surface and Cr subsurface segregation occurs in Co-rich CoCr alloys. However, in the presence of adsorbed oxygen, Pd and Cr occupy preferentially surface sites due to their lower electronegativity and thus stronger oxygen affinity compared to Pt and Co, respectively. In either cases, the calculated oxygen adsorption energies on the alloy surfaces are larger than on the pure components when the more noble components are present in the subsurface layers. |
| Databáze: | OpenAIRE |
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