Dynamic oxygen storage and release over Mn 0.1Ce 0.9O x and Mn 0.1Ce 0.6Zr 0.3O x complex compounds and structural characterization

Abstract

The dynamic oxygen storage capacity (DOSC) and rate (DOSR) over Mn 0.1Ce 0.9O x and Mn 0.1Ce 0.6Zr 0.3O x prepared by sol–gel method were investigated. The results show that Ce-based compounds containing Mn oxides with variable valences contribute to the majority of DOSC and DOSR performances at low temperature, and the DOSC and DOSR of Mn–Ce–O can be enhanced by the Zr addition at high temperature. Both materials were characterized by XRD, BET, Raman, TPR, EPR and XPS. XRD and Raman results indicate that Mn 0.1Ce 0.9O x and Mn 0.1Ce 0.6Zr 0.3O x are characterized with the fluorite-type cubic structure similar to CeO 2, and furthermore the thermal stability of M–Ce–O materials is improved by the introduction of some Zr atoms. EPR researches reveal that there are three types of Mn 2+ species: isolated Mn 2+ substituting for Ce 4+ ions in the lattice with a cubic symmetry, ones in defect with a noncubic symmetry and at the surface of samples. From XPS, it can be concluded that Mn 2+/Mn 3+ redox couples exist on the surface of Mn 0.1Ce 0.9O x and Mn 0.1Ce 0.6Zr 0.3O x samples.