Modulating of facets-dependent oxygen vacancies on ceria and its catalytic oxidation performance

To study the correlation between crystal facets and oxygen vacancies, three kinds of ceria samples with various crystal facets, cube [100], rod [110] and octahedron [111], were prepared. For further comparison, two kinds of ceria samples with [110] facets (20–30 nm rod and 5–8 nm filiform) were also constructed. The morphology, crystal structure, surface composition, reducibility and oxygen defects of the prepared samples were characterized by SEM, XRD, N2 adsorption–desorption, H2-TPR, XPS and EPR, respectively. The results showed that the surface oxygen defect contents of the samples followed the order: CeO2–F > CeO2–C > CeO2–R > CeO2–O, indicating that the content of oxygen vacancies is closely related on the crystal facets. The catalytic performance of the samples are all in line with that of the Oads/Olatt ratios, suggesting that crystal facets play a crucial role on surface oxygen vacancies and phenol oxidation of the ceria samples. Furthermore, although the CeO2–R sample (rods) and the CeO2–F sample (filiform) are mainly enclosed by [110] facets, the CeO2–F showed better catalytic performance than that of CeO2–R, revealing that the phenol oxidation not only depends on the crystal facets of CeO2 but also with its surface oxygen vacancy contents.