Binding and Reactive Sites in Metal Cluster Catalysts Homogeneous-Heterogeneous Bridges

Identification of Binding and Reactive Sites in Metal Cluster Catalysts Homogeneous-Heterogeneous Bridges 

One method of synthesizing a greater fraction of coordinatively unsaturated sites in a metal catalyst is to create smaller particles or clusters of the metal, as more atoms will be on the surface than on the inside of such a particle. There are several geometry-based correlations between the different populations of corner, edge, and terrace atoms as a function of particle size on variously shaped clusters [4, 5], 

Bridging Heterogeneous and Homogeneous Catalysis Concepts, Strategies, and Applications, First Edition. 

These correlations demonstrate that the number density of the most coordinatively unsaturated surface atoms (the corner atoms) increases sharply as a fraction of the total number of atoms, for particle sizes less than 2 nm. On the other hand, the same data demonstrate that the number density of less coordinatively unsaturated edge sites decreases gradually as particle sizes increases over 2 nm. As the particle size increases further beyond 2 nm, almost all surface atoms are located on terraces, which are the most coordinatively saturated of the surface atoms [4, 5]. 

More contemporary examples of synthesizing coordinatively unsaturated or open sites via heating have followed. Vidrak et al. [8] were able to increase the number of low coordinated aluminum ions along grain boundaries in y-AljOj using thermal treatments at 1073 K. Evidence for the increased number of Al ions in open coordination environments after thermal treatment came from a variety of 

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