Investigation in the influence of metal-support interactions on the thermal stability of CeO₂ nanorods

[Background] The oxygen vacancies concentration and thermal stability of CeO₂ based catalysts play an important role in their catalytic performance. However, the effect of metal loading on oxygen vacancy and thermal stability remains ambiguous. Therefore, a comprehensive and systematic method for elucidating the oxygen vacancies and the strong synergistic metal-support interactions in CeO₂ nanocrystals is desirable. [Purpose] This work aims to determine the relationship between the lattice constant and the concentration of oxygen vacancies, and to highlight the strong synergistic metal-support interactions in CeO₂ nanocrystals using bulk and surface characterization tools. [Methods] The samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma spectrometer (ICP). [Results] The XRD results indicate that the lattice constant of annealed CeO₂ was smaller than that of as-synthesized CeO₂ due to the decrease in oxygen vacancy concentration. Therefore, a linear relationship between lattice constant and oxygen vacancy concentration is established. Compared with as-synthesized and annealed CeO₂, Pt/CeO₂ nanorods present higher oxygen vacancy concentrations. The XPS, XRD and ICP results show that Pt diffuse into the CeO₂ during the annealing process. Hence, the strong synergistic metal-support interactions between Pt and CeO₂ protect the Pt clusters from further oxidation to PtO₂. [Conclusion] The relationship between lattice constant and the concentration of oxygen vacancies in CeO₂ shows that a decrease in lattice constant is related to the decrease in concentration of oxygen vacancies when CeO₂ is annealed in dry air. Moreover, the Pt loading distorts the lattice structure of CeO₂, thereby increasing its lattice strain and the lattice constant. Accordingly, Pt diffusion into CeO₂ at high temperature is responsible for the improved thermal stability of oxygen vacancy and Pt/CeO₂. (authors)