Inversion of Pattern Anisotropy During CO Oxidation on Pt(110) Correlated with Appearance of Subsurface Oxygen

Abstract

Spatiotemporal patterns occurring during the catalytic oxidation of carbon monoxide on Pt(110) show a strong anisotropy due to differences in the diffusion coefficients along the two major crystallographic axes of the catalyst: Reaction waves propagating parallel to the missing rows of the reconstructed Pt surface are much faster than reaction waves propagating in the perpendicular direction. In this Article, we report on the observation that, as a function of the exposure to reactant gases, the propagation velocities on the Pt surface change drastically, resulting in a complete reversal of the anisotropy. This observation is correlated with the appearance of subsurface oxygen in photoemission electron microscopic images of the reaction patterns.