Catalytic Oxidation of CO on a Curved Pt(111) Surface: Simultaneous Ignition at All Facets Through a Transient CO-O Complex

We combine PLIF and NAP-XPS to investigate the CO oxidation reaction at vicinal Pt(111) surfaces in the millibar regime, using a curved sample. We find that the catalytic activation of Pt occurs in all vicinal planes simultaneously,irrespectively of the reaction parameters. The systematic analysis of chemical species across the entire curved surface provides the clues for this surprising behavior. As the surface CO concentration decreases when approaching ignition, minor amounts of oxygen build up at both steps and (111) terraces. First-principles theory indicates that the latter is forming a CO-Pt-O complex that binds CO molecules to terraces strongly, leveling its adsorption energy to that of low-coordinated steps, and explaining why CO abruptly desorbs at the same temperature along the different crystal facets that make up the curved Pt surface.