Effect of Particle Morphology on the Ripening of Supported Pt Nanoparticles

To improve the understanding of sintering in diesel and lean-burn engine exhaust after-treatment catalysts, we examined oxygen-induced sintering in a model catalyst consisting of Pt nanoparticles supported on a planar, amorphous Al2O3 substrate. After aging at increasing temperatures, a transmission electron microscopy analysis reveals that a highly monodispersed ensemble of nanoparticles transformed into an ensemble with bimodal and subsequently Lifshitz-Slyozov-Wagner particle size distribution. Moreover, scanning transmission electron microscopy and atomic force microscopy analyses suggest that the Pt nanoparticle had size-dependent morphologies after sintering in the oxidizing environment. The evolution of the particle sizes is described by a simple kinetic model for ripening, and the size-dependent particle morphology is proposed as an explanation for the observed bimodal particle size distribution shape.