Cubooctahedron, small supported particle

CTP, see Cluster with terminal pseudo-atoms Cu. Pd -TSM, propylene gas-phase oxidation over, 39 320-322 Cubane, isomerization of, 24 148 Cubooctahedron, small supported particle model, 36 80-81... 

It seems plausible that the catalytic activity of small metal particles would be influenced by the crystal structure. Yacaman et al. (118) have studied pentane hydrogenolysis over Rh -A C, Rh/Si02, Rh/C, Rh/Ti02, and Rh/MgO. The support and preparation method, all for particles of d < 5 nm, determined whether cubooctahedrons or icosahedrons were formed, but the catalytic properties depended more on d than on crystal type. 

In general, in catalysis, the active centers are located at the surface so that the properties of metal particles are related to the number of surface atoms (Nj). The particles are very often characterized by their dispersion (D=Ns/N,) (N,=total number of atoms of the metal particle). Increasing the number of surface atoms (Ns) per total number of atoms (N,) requires particles of small sizes, typically in the nanometer range. Van Hardeveld and Hartog [66] proposed, a long time ago, that the shape of nanosized particles can be represented by cubooctahedrons. To our knowledge, even if this shape is a good model and is sometimes observed, there is no experimental proof that all particles have such a shape or preserve such structure at any temperature, especially when they are deposited on a support... 

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