A comparative study in structure and reactivity of “FeO x -on-Pt” and “NiO x -on-Pt” catalysts

Abstract

Oxide nanostructures grown on noble metal surfaces are often highly active in many reactions, in which the oxide/metal interfaces play an important role. In the present work, we studied the surface structures of FeO x -on-Pt and NiO x -on-Pt catalysts and their activity to CO oxidation reactions using both model catalysts and supported nanocatalysts. Although the active FeO1−x structure is stabilized on the Pt surface in a reductive reaction atmosphere, it is prone to change to an FeO2−x structure in oxidative reaction gases and becomes deactivated. In contrast, a NiO1−x surface structure supported on Pt is stable in both reductive and oxidative CO oxidation atmospheres. Consequently, CO oxidation over the NiO1−x -on-Pt catalyst is further enhanced in the CO oxidation atmosphere with an excess of O2. The present results demonstrate that the stability of the active oxide surface phases depends on the stabilization effect of the substrate surface and is also related to whether the oxide exhibits a variable oxidation state.