Orientation and morphology of iridium, rhodium and platinum nanocrystals in zeolite X

Abstract

Iridium, rhodium and platinum particles with sizes of a few nanometers grown inside the lattice of zeolite X were studied by electron microscopy. The metals form fcc crystallites which grow with their crystallographic axes parallel to the corresponding axes of the zeolite lattice. This orientation relationship is exploited to determine the morphology of the metal crystals. Rhodium and iridium crystallites are bounded almost exclusively by {111} surfaces and thus have more or less regular octahedral shapes. The platinum particles have less well-defined crystal shapes, but the {111} surfaces appear to predominate in these crystals also.