Effects of Fe-doping of ceria-based materials on their microstructural and dynamic oxygen storage and release properties

Abstract

The structural/textual characteristics and dynamic oxygen storage capacity (DOSC) of Fe0.1Ce0.9Ox and Fe0.1Ce0.6Zr0.3Ox samples prepared by sol–gel method are investigated by X-ray powder diffraction (XRD), Raman, Hydrogen temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS) and mass spectrometry with CO/O2 transient pulses. The dynamic oxygen storage capacity and rate are largely promoted by Fe doping, and their thermal stability is enhanced by Fe and Zr co-doping. The DOSC (at 673 K) are ordered as: Fresh: Fe0.1Ce0.6Zr0.3Ox (566.6 μmol/g) > Fe0.1Ce0.9Ox (551.8 μmol/g) > Ce0.67Zr0.33O2 (287.5 μmol/g) > CeO2 (140.3 μmol/g); Annealed1,173K: Fe0.1Ce0.6Zr0.3Ox (101.6 μmol/g) > Ce0.67Zr0.33O2 (45.3 μmol/g) > Fe0.1Ce0.9Ox (44.9 μmol/g) > CeO2 (43.3 μmol/g). The H2-TPR results showed that Fe-incorporation improve the total oxygen storage capacity (TOSC) of mixed oxide and low temperature activity. The TOSC are ordered as: Fe0.1Ce0.9Ox (1.53 mmol/g) > Fe0.1Ce0.6Zr0.3Ox (1.42 mmol/g) > Ce0.67Zr0.33O2 (1.16 mmol/g) > CeO2 (0.88 mmol/g). XRD and Raman results indicate that Fe0.1Ce0.9Ox and Fe0.1Ce0.6Zr0.3Ox are characterized with the fluorite-type cubic structure similar to CeO2. TPR and XPS analyses reveal that the introduction of Fe into ceria and ceria-zirconia mixed oxides strongly modified the structural and textural properties, which influenced the kinetics of bulk oxygen diffusion.