This is an attempt to develop a method for determining the oxidation state of surface layers of metal-oxide catalysts during a catalytic reaction. Up to now, such data have been unobtainable except under very unrealistic conditions. The method combines transient kinetics at atmospheric or near- atmospheric pressures with spectroscopy (especially Auger electron spectroscopy) under ultrahigh vacuum. Two types of oxides are studied: thick (micron-sized) films of one-and two-componement oxides on polycrystalline gold, and thin (nanometer-sized) films of spinels grown epitaxially on single crystals of gold. Raman spectroscopy and low-energy electron diffraction are used to characterize the films. Ethanol is used as a chemical probe; both acid-base and redox reactions are followed. Metal oxides are technologically important materials because of their strength, stability, and varied optical, electric, and magnetic properties. In the fabrication of oxides, as well as in many of their applications, surface properties are important. The materials studied in this project are typical of many multicomponent systems used in industrial applications. This investigation of the relationships between atomic structure, composition, oxidation state, and surface chemical reactivity therefore has wide applicability, especially for materials design using the principles of molecular architecture.
