2D-Arrays of Nanoparticles as Model Catalysts

From studies on supported model catalysts, we know that the reactivity of catalysts depends on the size and shape of the metal nanoparticles but also for some reactions it can depend on the distance between them. We discuss recent methods to prepare regular arrays of supported model catalysts. One of these methods is based on the growth of regular arrays of metal clusters on a template (graphene or h-BN monolayers or ultrathin oxide film on a metal single crystal) and allows the study of size effects down to clusters of a few atoms. A second method uses self-assembled micelles from diblock co-polymers, and produces hexagonal arrays of clusters on large area flat supports which are well suited to study effects of the size (1-10 nm) and of the density of clusters. A third method using colloidal synthesis is able to produce in large quantity metal nanoparticles with a very narrow size distribution and a single shape which spontaneously self-organize in regular arrays on a large area. This method is very promising for studying the effect of the shape of metal particles on catalytic activity and selectivity. We discuss also some other methods like electron beam or nanosphere lithography which are less promising for the fabrication of model catalysts. Finally we make some remarks about the likely evolution of studies on supported model catalysts.