Site-selective surface reactions: Hydrocarbon oxidation processes on oxidized Mo(110)

The site specificity for elementary steps important in hydrocarbon oxidatio n are investigated on oxidized Mo(110). Our studies illustrate how detailed mechanistic information is obtained about surface reactions by separating complex problems into elementary reaction steps on well-defined materials. This methodology is particularly powerful for the study of fundamental stru cture-reactivity relationships, including issues of site specificity. Metho ds for synthesizing and characterizing oxidized surfaces with specific type s of oxygen coordination are described to demonstrate how a model system ca n be constructed. We have focused on the C-O bond formation step in the oxi dation of methane via our investigations of methyl radical reactions with s urface oxygen and the microscopic reverse, methyl evolution from adsorbed m ethoxy. A combination of infrared and electron energy loss spectroscopies i s used to identify specific intermediates on the surface. Our results are d iscussed in terms of hydrocarbon oxidation on MoO3-based materials.