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

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 fee {111} facets above this size. Ph 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.