A Metastable State Facilitates Low Temperature CO Oxidation over Pt Nanoparticles

The dynamic response of heterogeneous catalytic materials to their environment opens a wide variety of possible surface states which may have increased catalytic activity. In this work, we find that it is possible to facilitate the oxidation of CO over metallic 2nm Pt nanoparticles at room temperature after performing a thermal treatment of a CO*-covered Pt catalyst. By combining pressure pulse experiments with in situ spectroscopy, we find that thermal treatment in the presence of adsorbed CO* is necessary to access this metastable state and that the state collapses after elevated thermal treatment or by further readsorption of CO at room temperature. The exact nature of this surface change remains open to speculation, but it is hypothesised that this metastable high-activity state is formed after desorption of weakly bound CO* molecules from well-coordinated Pt sites.