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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

Size-dependent melting temperature of palladium versus the size for different shapes.
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Figure 2: Size-dependent melting temperature of palladium versus the size for different shapes.

Mentions: The size-dependent melting temperatures of platinum and palladium are plotted in Figures 1 and 2 respectively. The materials properties of the considered materials are indicated in Table 1. The melting properties for the sphere have been calculated using for the solid surface energy the mean value of experimental data [13]. For the other polyhedra shapes, we have considered the fcc crystal structure of the metals and the respective solid surface energy for each face [14]. Tables 2 and 3 indicate the parameters used for the calculation of the melting properties. Experimentally, the melting of agglomerated Pt nanocrystals (tetrahedrons and cubes) with an average size around approximately 8 nm starts at approximately 900 K [15] in relative good agreement with our theoretical predictions. Molecular dynamics simulations [16] have calculated the size effect on the melting temperature of Pd and found ╬▒sphere = 0.95 nm while our theory predicts 1.68 nm.


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

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

Size-dependent melting temperature of palladium versus the size for different shapes.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: Size-dependent melting temperature of palladium versus the size for different shapes.
Mentions: The size-dependent melting temperatures of platinum and palladium are plotted in Figures 1 and 2 respectively. The materials properties of the considered materials are indicated in Table 1. The melting properties for the sphere have been calculated using for the solid surface energy the mean value of experimental data [13]. For the other polyhedra shapes, we have considered the fcc crystal structure of the metals and the respective solid surface energy for each face [14]. Tables 2 and 3 indicate the parameters used for the calculation of the melting properties. Experimentally, the melting of agglomerated Pt nanocrystals (tetrahedrons and cubes) with an average size around approximately 8 nm starts at approximately 900 K [15] in relative good agreement with our theoretical predictions. Molecular dynamics simulations [16] have calculated the size effect on the melting temperature of Pd and found ╬▒sphere = 0.95 nm while our theory predicts 1.68 nm.

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