The effect of precipitation pH on thermal stability and structure of Ce0.35Zr0.55(LaPr)0.1O2 oxides prepared by co-precipitation method

Cerium zirconium-based oxygen storage material is indispensable in improving the catalytic efficiency for TWCs. However, the synthesis mechanism is seldom investigated with a method by RE/Zr chloride and sodium hydroxide. Therefore, in this study, Ce0.35Zr0.55(LaPr)0.1O2 oxides were prepared by co-precipitation method at different precipitation pH. The relationships between pH and physicochemical properties of Ce0.35Zr0.55(LaPr)0.1O2 oxides were elucidated. The results showed that the obtained Ce0.35Zr0.55(LaPr)0.1O2 oxides exhibited homogenous phase structure, best thermal stability and highest oxygen storage capability at pH = 10. In order to analysis the results, the colloidal nuclear reaction model was proposed and the rationality of the model was clearly illustrated by measuring zeta potential (ζ), impurities content of Na+ and Cl− and pH variations of the co-precipitation reaction system. It was proved that the cerium zirconium mixed oxides precursor's surface potential was changed from positively charged to negatively charged along with the pH values changed from low to high and had iso-electric point (IEP) at pH = 8. In addition, the pH values of all solutions were reduced differently after the precipitation reaction. The model may provide a good reference for preparation cerium zirconium mixed oxides with different composition under chloride raw material system.