High resolution transmission electron microscopy of iridium, rhodium, and platinum nanocrystals in zeolite X

Abstract

Iridium, rhodium, and platinum particles with sizes of a few nm grown inside the lattice of zeolite NaX were studied by high resolution electron microscopy. The morphology of these particles exhibits a transition from rounded shapes below a diameter of 2 nm to well developed crystal shapes with atomically smooth fcc 111 facets above this size. Rh and Ir particles above 2 nm are bounded exclusively by 111 surfaces, while Pt particles also have rounded surface regions and 100 facets. Particles above 2 nm grow in an orientation relationship with the zeolite lattice.