Effects of Ni-Doping of Ceria-Based Materials on Their Micro-Structures and Dynamic Oxygen Storage and Release Behaviors

Abstract

The structural, textural, and dynamic oxygen storage/release behaviors of Ni0.1Ce0.9Ox and Ni0.1Ce0.6Zr0.3Ox (prepared by sol–gel method) are investigated by X-ray diffraction (XRD), Raman, H2-TPR, X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and CO/O2 pulses with mass spectrometry studies. The dynamic oxygen storage capacity and rate are largely promoted by Ni doing, and the thermal stability of the sample is also enhanced. XRD and Raman results indicate that Ni0.1Ce0.9Ox and Ni0.1Ce0.6Zr0.3Ox have the fluorite-type cubic structure similar to CeO2. TPR, EPR, and XPS analyses reveal that the introduction Ni into ceria and ceria–zirconia mixed oxides strongly modifies the structural and textural properties, which influence the kinetics of bulk oxygen diffusion. The dynamic oxygen storage capacity (DOSC) of Ni doped samples (Ni0.1Ce0.9Ox and Ni0.1Ce0.6Zr0.3Ox) and reference samples (CeO2 and Ce0.67Zr0.33O2) were investigated with CO/O2 transient pulses. The results show that Ce-based materials containing Ni oxides with variable valences contribute to the majority of DOSC and DOSR performances, and the stability of DOSC is obviously enhanced by Ni and Zr codoping.