Effect of preparation method on the surface and redox properties of Ce0.67Zr0.33O2 mixed oxides

Four types of Ce0.67Zr0.33O2 (CZC, CZH, CZM and CZS) mixed oxides were prepared by the coprecipitation, hydrothermal, microemulsion and sol-gel methods, respectively, and were characterized by the XRD, BET, SEM and TPR analyses. It is found that TPR of CeO2ZrO2 depends on two main factors, phase homogeneity and textural properties. By enhancing the homogeneity of the Ce and Zr atoms in the mixed oxides with appreciate surface area, CZS shows the best low-temperature reducibility. After calcinations at 950 °C for 20 h, however, the greatly reduced surface area results in the disappearance of a reduction of surface Ce4+, and only one peak remains in the TPR profile of CZS, which is an intrinsic feature of bulk oxygen reduction and depends on the material. Meanwhile, the phase segregation strongly affects the hydrogen uptake behavior of CZC and CZH after aging. The favorable thermal stability in both structural and textural properties brings a promise of the application of a reverse microemulsion synthesis to prepare CeO2ZrO2 mixed oxides to meet the increasingly stringent requirement of service life of three-way catalysts.