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.

Catalytic performance and stability of Fe-doped CeO2 in propane oxidative dehydrogenation using carbon dioxide as an oxidant

Propane oxidative dehydrogenation (ODH) in the presence of CO₂ was investigated over a series of Fe-doped CeO₂ catalysts.

Cu/CeO2 Catalyst for Water-Gas Shift Reaction: Effect of CeO2 Pretreatment

CuO/CeO₂ is a kind of promising catalysts for the water-gas shift (WGS) reaction. Efforts were put in to improve its performance through modification of CeO₂ support. In this study, portions of CeO₂ prepared by a co-precipitation method were separately annealed at 300 °C in air, under vacuum and with H₂ , and were used as supports for the fabrication of CuO/CeO₂ catalysts. The physicochemical properties of the catalysts were characterized by X-ray diffraction, N₂ -physisorption, inductively coupled plasma, Raman spectroscopy, CO₂ temperature-programmed desorption, and H₂ temperature-programmed reduction techniques. The relation between catalytic performances and physicochemical properties of the CuO/CeO₂ catalysts were discussed. Among the three catalysts, the one with CuO supported on H₂ -reduced CeO₂ shows the highest catalytic activity, mainly due to strong CuO-CeO₂ synergetic interaction and high concentration of Frenkel-type oxygen vacancies. The superior catalytic activities can also be attributed to the Cu⁰ crystals of small size and the oxygen vacancies in non-stoichiometric CeO_2-x .

Influence of local structure on photoluminescence properties of Eu3+ doped CeO2 red phosphors through induced oxygen vacancies by contrasting rare earth substitutions

A new family of red phosphors, Ce_0.9-xRE_xO_2-δ:0.1Eu³⁺ (RE = Y and La; x = 0, 0.20, 0.40, 0.60, 0.80, and 0.90), was synthesized by a conventional solid-state route. The influence of contrasting rare earth substitutions (Y and La) in the system was investigated on the local structure and associated photoluminescence properties by various characterization techniques. Both trivalent ion substitutions lead to the same kind of variation during phase transformation from fluorite to the respective parent oxide structure (x ≥ 0.6). On the other hand, the substitutions have a distinct effect on local structure, absorption, luminescence and lifetimes. The smaller Y³⁺ ion substitution enables the ordering of oxygen vacancies in a lattice, inhibiting the defect formation of Ce³⁺ oxidation states. In contrast, the larger La³⁺ ion substitution liberates oxygen vacancies, allowing defect formation. Consequently, the concentration of Ce³⁺ is dependent on the ionic radius of the metal ions and it has a bearing on the band gap and luminescence properties of the system. Ce_0.1Y_0.8O_2-δ:0.1Eu³⁺ phosphor exhibited maximum red emission intensity at 612 nm, which is 8 times higher than that of Ce_0.9O_2-δ:0.1Eu³⁺ and better than that of commercial Philips red phosphor, whereas La substitution yielded poor emission intensities with higher concentrations. The co-substitution of contrasting rare earth metals with Eu³⁺ allow the understanding of local structure and a smaller ion like Y³⁺ greatly functionalizes CeO₂:Eu³⁺ phosphor.