Enhanced thermal stability and oxygen storage capacity of ceria-zirconia prepared by flame spray pyrolysis under high temperature

Abstract

Ceria zirconia solid solution with high oxygen storage capacity (OSC) and thermal stability under 1000 ​°C is quite important for support materials in three-way catalysts (TWCs). In this work, Ce1-xZrxO2 with different Zr dopants (x ​= ​0, 0.125, 0.250 and 0.375) have been prepared by flame spray pyrolysis (FSP) with carboxylic acid or ethanol and carboxylic acid (v:v 1:4) solvents. The influences of Zr content and the addition of ethanol into carboxylic acid on the OSC performance and thermal stability have been systematically characterized by X-ray diffraction (XRD), N2 adsorption-desorption, Raman analysis, field emission scanning electron microscope (FESEM), high resolution transmission electron microscope (HRTEM), X-ray photoelectron spectroscopy (XPS), hydrogen-temperature programmed reduction (H2-TPR), and pulse thermal analysis using H2 as reducing agent. The presence of cubic-tetragonal interfaces in the Ce0.750Zr0.250O2 sample can enhance the formation of oxygen vacancies and the mobility of lattice oxygen in ceria-zirconia solutions, which results in the largest OSC (349 ​μmol ​g−1) among the fresh samples. The cubic-tetragonal interfaces in the Ce0.750Zr0.250O2 sample can also promote the thermal stability under 1000 ​°C to preserve better OSC (202 ​μmol ​g−1) than other aged samples. Furthermore, after adding with ethanol into carboxylic acid solvent, the OSC of the sample further increases to 371 ​μmol ​g−1 for the increment of oxygen vacancy concentration. It is worthy to note that the introduction of ethanol can suppress Zr migration from the lattice to the surface of CeO2 at high temperature, further enhancing OSC (240 ​μmol ​g−1) and thermal stability.