CO Oxidation of Pt Nanostructures Supported by TiO₂/Ti

This study examined the CO oxidation reactivity of Pt deposited on TiO₂. The Pt catalysts were prepared by the evaporation of Pt on Ti foils covered with TiO₂, and their surface structures were characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Separate Pt nanoparticles could be observed with lower amounts of deposited Pt (<2 nm). With increasing Pt thickness, these Pt nanoparticles appeared to agglomerate into more complicated nanostructures. When approximately 5 nm of Pt was deposited, the TiO₂ surface was almost completely covered by Pt. Additional deposition of Pt on these complete Pt-layers resulted in the deposition of small nanoparticles (∼5 nm) on top of the Pt underlayer. The CO oxidation reactivity at 160 °C, normalized with respect to the Pt thickness, initially decreased with increasing amount of Pt. This was attributed mainly to the decrease in the surface-to-volume ratio. However, the reactivity increased when the amount of Pt exceeded 5 nm, which can be rationalized in part by the unique structural properties of Pt-films according to SEM imaging. We also suggest that a stronger influence of the metal-support interactions at lower Pt coverages results in reduced catalytic activity.