Solvothermal synthesis of CeO₂-ZrO₂-M₂O₃ (M = La, Y, Bi) mixed oxide and their soot oxidation activity

CeO₂-ZrO₂-M₂O₃ (M = La, Y, Bi) mixed oxide has been prepared by a solvothermal synthesis method. The physico-chemical properties of the mixed oxide have been studied by X-ray powder diffraction (XRD), Raman spectroscopy, BET, X-ray photoelectron spectroscopy (XPS), TEM and temperature-programmed reduction (TPR), and the catalytic activity for soot oxidation has been studied by thermogravimetry (TG). La³⁺, Y³⁺ and Bi³⁺ exhibit positive effects on lowering the oxidation temperature of the soot. The XRD and Raman results showed formation of mixed oxides and TEM images suggested the nanosized nature of the particles. The benefit of yttrium or lanthana doping on the catalytic activity of ceria can be related to active oxygen formation provoked by the defective structure of ceria due to the presence of La³⁺ and Y³⁺. The benefit of Bi³⁺ doping on catalytic activity can be related to the reduction at low temperature both with Bi₂O₃ and ceria.