Size-dependent catalytic and melting properties of platinum-palladium nanoparticles
1 Institute of Mechanics, Materials and Civil Engineering, Catholic University of Louvain, 2 Place Sainte Barbe, 1348 Louvain-La-Neuve, Belgium
2 Yili Normal University, 298 Jie Fang Lu Street, Yi Ning Shi, Xinjiang, China
3 Institute of Electronics, Microelectronics and Nanotechnology, Scientific City, Avenue Henri Poincaré BP60069, 59652 Villeneuve d'Ascq, France
Nanoscale Research Letters 2011, 6:396 doi:10.1186/1556-276X-6-396Published: 26 May 2011
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.
65.80-g; 82.60.Qr; 64.75.Jk