The physical structure of a catalyst can significantly influence its activity and selectivity. Catalysts often possess a hierarchical structure with features ranging from the atomic to the macroscopic scale. This includes nanoparticles, mesoporous materials, and bulk phases. The interplay between these different scales can lead to unique catalytic properties that are not evident in simpler systems. For instance, the size and shape of metal nanoparticles can affect the availability and nature of active sites.
