Structural Insight into Strong Pt–CeO2 Interaction: From Single Pt Atoms to PtOx Clusters

Pt–CeO2 nanocomposites were obtained by coprecipitation, varying the Pt loading over a wide range of 1–30 wt %. The samples were calcined in air at 450–1000 °C. The Pt–CeO2 nanocomposites were investigated by a set of structural (X-ray diffraction, extended X-ray absorption fine structure (EXAFS), pair distribution function (PDF), and transmission electron microscopy) and spectroscopic (X-ray photoelectron spectroscopy and Raman spectroscopy) methods. Over the whole range of Pt loading, the main species were Pt2+ and Pt4+. They were localized either in a single-atom state or in the form of PtOx clusters on the ceria surface. The joint PDF and EXAFS modeling based on the combination of [Pt2+O4] single-atom and Pt3O4 structural fragments allowed us to propose the local structure of the PtOx clusters. The formation of such surface structures is associated with a distorted ceria surface on the Pt–CeO2 nanocomposites. We assume that the close arrangement of platinum ions in the PtOx clusters could be responsible for the effective redox properties of the samples.