PNNL

Abstract

The interaction between metal particles and their oxide support can be strong so as to affect the reactivity of a catalyst system by, for example, encapsulation of the particles by the oxide. Direct observation of metal-oxide interfaces with atomic resolution is a challenge and can only be achieved by cross sectional high-resolution transmission electron microscopy (HRTEM). With this approach, we found partial encapsulation of Pd particles by reduced ceria-zirconia in a model, single-crystal thin film auto catalyst, indicating a strong interaction between Pd and the oxide. Besides obtaining HRTEM images, the valence of cerium was determined by electron energy loss spectroscopy (EELS). The effect of reduction and oxidation conditions on this interaction provides a qualitative explanation for a previously observed reversible reactivation of oxygen storage in model powder auto catalysts. The technique of cross sectional HRTEM can be applied to the study of other metal-particle-on-oxide systems.