Correlations between Oxygen Uptake and Vacancy Concentration in Pr-Doped CeO2

The oxygen uptake of a series of Pr-CeO2 materials was measured using thermogravimetric analysis at 420 and 600 degrees C, and at both temperatures, 20% Pr-CeO2 was found to have the highest uptake. The materials were characterized using X-ray diffraction and scanning transmission electron microscopy. Defects in the materials were identified using Raman spectroscopy, and ultraviolet-visible spectroscopy was used to show the presence of Pr cations in the +3 oxidation state. The existence of these species was attributed to be responsible for the ability of the materials to uptake oxygen. Electron energy loss spectroscopy was used to investigate the effect of Pr addition to CeO2; the Ce M-5/M-4 and O I-B/I-C ratios were calculated to indicate the relative changes in the Ce3+ and oxygen vacancy concentration, respectively. There was no observable increase in the Ce3+ concentration; however, the oxygen vacancy concentration increased with an increase in the Pr content. Thus, Pr increases the defect concentration and the ability of the materials to uptake oxygen.