Clusters, surfaces, and catalysis.
The surface science of heterogeneous metal catalysis uses model systems ranging from single crystals to monodispersed nanoparticles in the 1-10 nm range. Molecular studies reveal that bond activation (C-H, H-H, C-C, CO) occurs at 300 K or below as the active metal sites simultaneously restructure. The strongly adsorbed molecules must be mobile to free up these sites for continued turnover of reaction. Oxide-metal interfaces are also active for catalytic turnover. Examples using C-H and CO activation are described to demonstrate these properties. Future directions include synthesis, characterization, and reaction studies with 2D and 3D monodispersed metal nanoclusters to obtain 100% selectivity in multipath reactions. Investigations of the unique structural, dynamic, and electronic properties of nanoparticles are likely to have major impact in surface technologies. The fields of heterogeneous, enzyme, and homogeneous catalysis are likely to merge for the benefit of all three.