(609e) Morphology And Diffusion Mechanism Of Platinum Nanoparticles On Carbon Nanotube Bundles

Molecular dynamics simulations were used to investigate the mobility and morphology of platinum nanoparticles supported on carbon-based materials. The embedded-atom method was used to model Pt-Pt interactions, and the Pt-C interactions were modeled using the Lennard-Jones potential. The supports considered include a single graphite layer as well as carbon nanotubes, regarded as bundles. In all supports the carbon atoms were held fixed. The goal of our work is to assess the effect of the substrate morphology on the properties of the metal nanoparticles. The properties of interest include the mobility and morphology of the supported nanoparticles. Our results show that the diffusion coefficients of Pt nanoparticles on carbon nanotube bundles are one order of magnitude lower than those of Pt nanoparticles supported by graphite. Density profiles, radial distribution functions, and average coordination numbers were calculated to study the structure of the supported nanoparticles. Pt nanoparticles deposited on carbon nanotubes differ structurally from those deposited on graphite. In particular, they are characterized by a lower average coordination number than those supported by graphite. These results suggest that the catalytic properties of supported Pt nanoparticles can be tuned by changing the substrate and may provide partial explanation of recent experimental studies according to which metal nanoparticles deposited on carbon nanotubes yield effective catalysts. We have also conducted simulations with flexible nanotubes, using the Tersoff potential to model the C-C interactions. Preliminary results show that Pt nanoparticles can cause deformation of the nanotubes, and that the strength of the Pt-C interaction has a significant effect on the amount of this deformation. Our preliminary results suggest that it is possible to control which Pt crystallographic plane is exposed, a significant step towards the preparation of 100% selective catalysts (G.A. Somorjai and R.M. Rioux, Catalysis Today 100 (2005) 201-215).