Catalysis Science of Surface Metal Oxide Catalytic Active Sites
Israel E. Wachs, Lehigh University, Department of Chemical Engineering, Iacocca Hall, 111 Research drive, Behtlehem, PA 18015-4791
Surface metal oxide sites represent the catalytic active sites present in oxide-based catalytic materials (zeolites, supported metal oxides, heteropolyoxo anions, bulk mixed metal oxides and clays). Recent in situ and operando Raman, IR and UV-Vis DRS characterization advances are allowing for the complete determination of the molecular and electronic structures of the surface metal oxide catalytic active surface sites under reaction conditions. Combination of the molecular and electronic structural information with the corresponding kinetics of the surface chemistry is allowing, for the first time, the establishment of molecular/electronic structure-activity/selectivity relationships. These fundamental studies with molecularly designed metal oxide catalysts are allowing for the direct determination of the number of catalytic active sites involved in a specific catalytic reaction (one, two or greater), the relative contributions of isolated and polymeric surface metal oxide sites as well as oxide nanoparticles, the role of the oxide support ligand, the effect of cation oxidation state, and the mechanism by which promoters influence specific catalytic reactions.