Synthesis and Oxygen Storage Capacities of Yttrium-Doped CeO₂ with a Cubic Fluorite Structure

Doping CeO2 with Y cations was achieved in this study using three strategies: doping only during the hydrothermal process (H-Y-doped CeO2), doping only during the impregnation process (I-Y-doped CeO2), and doping during both the hydrothermal and impregnation processes (H/I-Y-doped CeO2). During the three synthesis strategies of Y-doped CeO2, these Y ions could be incorporated into the CeO2 lattice in the +3 state while holding the cubic fluorite structure, and no impurity phases were detected. Pure CeO2 crystal itself contained a certain number of intrinsic VO defects, and Y-doping was beneficial for the creation of extrinsic VO defects. The relative concentrations of VO defects were quantified by the values of A592/A464 obtained from Raman spectra, which were 1.47, 0.93, and 1.16 for the H-Y-, I-Y-, and H/I-Y-doped CeO2, respectively, and were higher than that of the undoped one (0.67). Moreover, the OSCs of the three Y-doped CeO2 were enhanced, and the sequence of OSCs was: H-Y-doped CeO2 (0.372 mmol/g) > H/I-Y-doped CeO2 (0.353 mmol/g) > I-Y-doped CeO2 (0.248 mmol/g) > Undoped CeO2 (0.153 mmol/g); this result was in good agreement with the Raman spectroscopy results.