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Size-dependent catalytic and melting properties of platinum-palladium nanoparticles.

Guisbiers G, Abudukelimu G, Hourlier D - Nanoscale Res Lett (2011)

Bottom Line: The melting temperature, melting enthalpy, and catalytic activation energy were found to decrease with size.The predictions were compared with the available experimental data in the literature.PACS: 65.80-g; 82.60.Qr; 64.75.Jk.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Mechanics, Materials and Civil Engineering, Catholic University of Louvain, 2 Place Sainte Barbe, 1348 Louvain-La-Neuve, Belgium. gregory.guisbiers@physics.org.

ABSTRACT
While nanocatalysis is a very active field, there have been very few studies in the size/shape-dependent catalytic properties of transition metals from a thermodynamical approach. Transition metal nanoparticles are very attractive due their high surface to volume ratio and their high surface energy. In particular, in this paper we focus on the Pt-Pd catalyst which is an important system in catalysis. The melting temperature, melting enthalpy, and catalytic activation energy were found to decrease with size. The face centered cubic crystal structure of platinum and palladium has been considered in the model. The shape stability has been discussed. The phase diagram of different polyhedral shapes has been plotted and the surface segregation has been considered. The model predicts a nanoparticle core rich in Pt surrounded by a layer enriched in Pd. The Pd segregation at the surface strongly modifies the catalytic activation energy compared to the non-segregated nanoparticle. The predictions were compared with the available experimental data in the literature. PACS: 65.80-g; 82.60.Qr; 64.75.Jk.

No MeSH data available.


Related in: MedlinePlus

Phase diagram of the Pt-Pd system considering the surface segregation effect. Surface segregation effect at a size equal to 4 nm for a spherical nanoparticle.
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Figure 4: Phase diagram of the Pt-Pd system considering the surface segregation effect. Surface segregation effect at a size equal to 4 nm for a spherical nanoparticle.

Mentions: Considering the surface segregation in the Pt-Pd system, we can see in Figure 4 that the lens shape of the surface liquidus/solidus curves is deformed compared to the core. At a given temperature, the liquidus and solidus curves of the surface are enriched in Pd compared to the core; meaning that the surface is depleted of Pt (the higher bond energy element) which is in agreement with experimental observations[27-29] and other theoretical calculations[29-31]. This is due to the fact that Pd has a lower solid surface energy, a lower cohesive energy compared to Pt and also because diffusion is enhanced at the nanoscale [32].


Size-dependent catalytic and melting properties of platinum-palladium nanoparticles.

Guisbiers G, Abudukelimu G, Hourlier D - Nanoscale Res Lett (2011)

Phase diagram of the Pt-Pd system considering the surface segregation effect. Surface segregation effect at a size equal to 4 nm for a spherical nanoparticle.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211490&req=5

Figure 4: Phase diagram of the Pt-Pd system considering the surface segregation effect. Surface segregation effect at a size equal to 4 nm for a spherical nanoparticle.
Mentions: Considering the surface segregation in the Pt-Pd system, we can see in Figure 4 that the lens shape of the surface liquidus/solidus curves is deformed compared to the core. At a given temperature, the liquidus and solidus curves of the surface are enriched in Pd compared to the core; meaning that the surface is depleted of Pt (the higher bond energy element) which is in agreement with experimental observations[27-29] and other theoretical calculations[29-31]. This is due to the fact that Pd has a lower solid surface energy, a lower cohesive energy compared to Pt and also because diffusion is enhanced at the nanoscale [32].

Bottom Line: The melting temperature, melting enthalpy, and catalytic activation energy were found to decrease with size.The predictions were compared with the available experimental data in the literature.PACS: 65.80-g; 82.60.Qr; 64.75.Jk.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Mechanics, Materials and Civil Engineering, Catholic University of Louvain, 2 Place Sainte Barbe, 1348 Louvain-La-Neuve, Belgium. gregory.guisbiers@physics.org.

ABSTRACT
While nanocatalysis is a very active field, there have been very few studies in the size/shape-dependent catalytic properties of transition metals from a thermodynamical approach. Transition metal nanoparticles are very attractive due their high surface to volume ratio and their high surface energy. In particular, in this paper we focus on the Pt-Pd catalyst which is an important system in catalysis. The melting temperature, melting enthalpy, and catalytic activation energy were found to decrease with size. The face centered cubic crystal structure of platinum and palladium has been considered in the model. The shape stability has been discussed. The phase diagram of different polyhedral shapes has been plotted and the surface segregation has been considered. The model predicts a nanoparticle core rich in Pt surrounded by a layer enriched in Pd. The Pd segregation at the surface strongly modifies the catalytic activation energy compared to the non-segregated nanoparticle. The predictions were compared with the available experimental data in the literature. PACS: 65.80-g; 82.60.Qr; 64.75.Jk.

No MeSH data available.


Related in: MedlinePlus