CeO₂–MO _x (M: Zr, Ti, Cu) mixed metal oxides with enhanced oxygen storage capacity

The effect of composition on the thermal stability and oxygen storage capacity (OSC) of a series of CeO₂–MOx (M: Zr, Ti, Cu) mixed oxides was investigated. X-ray diffraction, N₂ adsorption–desorption analysis (BET), transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy were used to examine structural and microstructural properties. The total OSC of the fresh and aged mixed oxides were measured using thermogravimetric–differential thermal analysis at 600 °C, under alternating reductive and oxidative environment. Ceria doping was found to be effective toward an enhancement of its redox properties. The addition of Zr⁴⁺ into the CeO₂ lattice was found to have the least effect in enhancing the catalytic properties. In contrast with other studies in the literature [1, 2], increasing ZrO₂ content led to an increase of the OSC of the samples of up to 522 μmol O₂ g⁻¹ for 75 % Zr⁴⁺ content. On the other hand, the CeO₂–CuO with (1:3) molar ratio showed an almost three times higher OSC value than CeO₂–ZrO₂, which is deemed in the literature as one of the most promising OSC materials. In this work, the highest OSC values (1565 μmol-O₂ g⁻¹) were obtained for the fresh sample with CeO₂–CuO (25:75) composition. The CeO₂–CuO (25:75) mixed oxide still showed the highest OSC values with an only 6 % drop of OSC after aging at 900 °C for 6 h among all aged catalysts. On the other hand, ZrO₂ containing samples showed the best thermal resistance against aging.