Tailoring thermal stability of ceria-zirconia mixed oxide by doping of rare earth elements: From theory to experiment

Abstract

Ceria-zirconia mixed oxides (CZMO) are widely used in many important catalysis fields. However, pure CZMO is known to have poor thermal stability. In this paper, a strategy was proposed to design Ce0.475Zr0.475M0.05O2 (M = La, Y, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Er, Lu, and, Yb) oxide surface with high thermal stability by using first-principles molecular dynamics (FPMD) simulation and experiment method. Through the structure stability analysis at different temperatures, the surface energy γ as a function of Rion/Dave is identified as a quantitative structure descriptor for analyzing the doping effect of rare earth (RE) elements on the thermal stability of Ce0.475Zr0.475M0.05O2. By doping the suitable RE, γ can be adjusted to the optimal range to enhance the thermal stability of Ce0.475Zr0.475M0.05O2. With this strategy, it can be predicted that the sequence of thermal stability improvement is Y > La > Gd > Nd > Pr > Pm > Sm > Eu > Tb > Er > Yb > Lu, which was further verified by our experiment results. After thermal treatment at 1100 °C for 10 h, the specific surface area (SSA) of aged Y-CZ and La-CZ samples can reach 21.34 and 19.51 m2/g, which is 63.02% and 49.04% higher than the CZMO sample without doping because the surface doping of Y and La is in favor of inhibiting the surface atoms thermal displacement. In a word, the strategy proposed in this work can be expected to provide a viable way for designing the highly efficient CZMO materials in extensive applications and promoting the usages of the high-abundance rare-earth elements Y and La.