(617g) 2-D Wulff Construction of FeOx Islands Grown on Pt(111) for Use in Catalysis

Supported ultra-thin metal oxide films grown on metallic surfaces garner substantial interest in their ability to solve hosts of engineering problems, ranging from micro-electronics, protective coatings, magnetic devices and catalysis. Much of research being performed on these materials involves understanding the long-range structures, magnetic and optical properties of these films. For their use in catalysis, however, it is generally accepted that the reactions of interest occur at the interface created by the edge of the film and the substrate. A clear example of this is that FeO_x films supported on Pt(111) have shown improved performance for the CO oxidation reaction. Normally, a Pt(111) surface is rather inactive for the oxidation of CO, but the addition of a monolayer FeO_x film on the Pt enhances the catalytic properties by several orders of magnitude. Several experimental and computational studies infers that this reaction occurs through a bifunctional mechanism with the reaction is occurring at the interface between FeO and Pt(111). But the nature of this interface is not well understood and as with all catalysts, it is essential that one gains an understanding of the nature of the active site to elucidate how the reaction could proceed. This work first uses Density Functional Theory to examine a series of possible edge and corner structures that could be present for FeO_x islands supported on Pt(111). This information can be then translated into the creation of 2D Wulff constructions, allowing for the determination of the oxidation state and ratio of the different edges or a range of conditions. In addition, the thermodynamically predicted size of the FeO_x islands is also studied, where it is observed that the calculated island size drops as the island becomes more oxidized. This methodology would allow for an estimate of the conditions that would facilitate the edges that are the most reactive towards certain reactions.