Models of metal catalysts: beyond single crystals

Abstract

Because solid catalysts are typically complex in structure and composition, researchers have often used structurally simple models in attempts to identify catalytic sites and understand reaction mechanisms. Among models of metal catalysts, single crystals are the prototypes, but, because they cannot represent support effects or the smallest metal clusters and cannot easily be used in long-term catalyst testing, they are complemented by other types of model catalysts, including metal particles on well-defined planar supports and nearly molecular clusters of a few metal atoms each on metal oxide and zeolite supports. This account is a comparison of the various types of model metal catalysts and a summary of the advantages and limitations of each. Examples of rhodium and of platinum catalysts are given to illustrate the catalyst types and connections between them. More data are needed as a basis for comparisons of the performance of the various model catalysts.