Catalysis on faceted noble-metal nanocrystals: both shape and size matter

Experimental studies with single-crystal surfaces and computational simulations have long established that the activity and selectivity of a heterogeneous catalyst for a structure-sensitive reaction can be maximized by controlling the arrangement of atoms on the surface. The essence of these studies, however, could not be materialized until very recently when it became possible to generate faceted nanocrystals with controlled shapes and sizes, including those with high-index facets. In principle, the size of a faceted nanocrystal determines the surface-to-bulk atomic ratio and the proportions of different types (e.g. vertex, edge, and face) of atoms while the shape governs the types of facets on its surface and thus the arrangement of face atoms. Additionally, the adsorption of atomic/molecular species during the synthesis of nanocrystals and operation of a catalytic reaction can alter their shape and thus their durability as a catalyst. All of these issues need to be fully understood and addressed in the design, synthesis, and utilization of faceted noble-metal nanocrystals for catalytic applications.