Effect of particle morphology on the ripening of supported Pt nanoparticles

Artikel i vetenskaplig tidskrift, 2012

To improve the understanding of sintering in diesel and lean-burn engine exhaust aftertreatment catalysts, we examined oxygen-induced sintering in a model catalyst consisting of Pt nanoparticles supported on a planar, amorphous Al2O3 substrate. After ageing at increasing temperatures, transmission electron microscopy analysis reveals that highly monodisperse ensembles of nanoparticles transformed into ensembles with bimodal and subsequently Lifshitz-Slyozov-Wagner particle size distributions. Moreover, scanning transmission electron microscopy and atomic force microscopy analysis suggest that the Pt nanoparticles have size-dependent morphologies after sintering in 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 shapes.