Oxygen activation on the interface between Pt nanoparticles and mesoporous defective TiO₂ during CO oxidation

Platinum-based heterogeneous catalysts are mostly used in various commercial chemical processes because of their high catalytic activity, influenced by the metal/oxide interaction. To design rational catalysts with high performance, it is crucial to understand the relationship between the metal-oxide interface and the reaction pathway. Here, we investigate the role of oxygen defect sites in the reaction mechanism for CO oxidation using Pt nanoparticles supported on mesoporous TiO₂ catalysts with oxygen defects. We show an intrinsic correlation between the catalytic reactivity and the local properties of titania with oxygen defects (i.e., Ti³⁺ sites). In situ infrared spectroscopy observations of the Pt/mesoporous TiO_2-x catalyst indicate that an oxygen molecule bond can be activated at the perimeter between the Pt and an oxygen vacancy in TiO₂ by neighboring CO molecules on the Pt surface before CO oxidation begins. The proposed reaction pathways for O₂ activation at the Pt/TiO_2-x interface based on density functional theory confirm our experimental findings. We suggest that this provides valuable insight into the intrinsic origin of the metal/support interaction influenced by the presence of oxygen vacancies, which clarifies the pivotal role played by the support.