Comparative study of CeO2 and doped CeO2 with tailored oxygen vacancies for CO oxidation.

We report on the preparation and characterization of CeO(2) nanofibers (CeO(2)-NFs) and nanocubes (CeO(2)-NCs), as well as Sm- and Gd-doped CeO(2) nanocubes (Sm-CeO(2)-NCs and Gd-CeO(2)-NCs), synthesized by a simple hydrothermal process for CO catalytic oxidation. The samples were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), Raman spectroscopy, and photoluminescence spectroscopy. Their oxygen-storing capacity (OSC) was examined by means of hydrogen temperature-programmed reduction (H(2)-TPR) and oxygen pulse techniques. Their catalytic properties for CO catalytic oxidation were comparatively investigated. The results showed that the CeO(2)-NFs possessed a higher catalytic activity compared to the CeO(2)-NCs because of their smaller size and the greater number of oxygen vacancies. The activity of the Sm-CeO(2)-NCs was higher than that of the CeO(2)-NCs due to an increase in the number of oxygen vacancies, which results from the substitution of Ce(4+) species with Sm(3+) ions. In contrast, Gd doping had a negative effect on the CO catalytic oxidation due to the special electron configuration of Gd(3+) (4f(7)). Our work demonstrates that the oxygen vacancies in pure CeO(2) and the electron configuration of the dopants in doped CeO(2) play an important role in CO oxidation.