  In this work, we study the influence of the average crystallite size and
dopant oxide on the reducibility of CeO2-based nanomaterials. Samples were
prepared from commercial Gd2O3-, Sm2O3- and Y2O3-doped CeO2 powders by
calcination at different temperatures ranging between 400 and 900C and
characterized by X-ray powder diffraction, transmission electron microscopy and
BET specific surface area. The reducibility of the samples was analyzed by
temperature-programmed reduction and in situ dispersive X-ray absorption
spectroscopy techniques. Our results clearly demonstrate that samples treated
at lower temperatures, of smallest average crystallite size and highest
specific surface areas, exhibit the best performance, while Gd2O3-doped ceria
materials display higher reducibility than Sm2O3- and Y2O3-doped CeO2.
