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

Abstract

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.