Binary and Multicomponent Metal Catalysts

Reactions involving large (e.g., organic) molecules require a certain coordination between several closely spaced surface sites. The smaller the crystallite, the smaller will be the probability of finding segments offering a favorable coordination. 

Differences in the parameters of the electron gas between fine crystallites and the compact metal or large crystals. 

According to EXAFS experiments, the number of oxygen atoms relative to metal atoms in the air-oxidized state is much higher in fine crystallites than in large crystals, so that their behavior approaches that of oxides. 

Experimental observations exist according to which a foreign substrate may influence the catalytic properties of the microcrystalline metal supported by it, and the supported metal conversely may influence the catalytic properties of the substrate. 

A quantitative investigation of the influence exerted by a substrate on the properties of disperse catalysts is hampered by the distorting effects of many other factors, particularly the macrokinetic limitations and the size effects mentioned in Section 28.5.4. 

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