engleski

Oxygen-induced structural transformation of pyrochlore Ce2Zr2O7+x to the k-Ce2Zr2O8 phase

The temporary storage of oxygen in a solid catalyst is imperative for many important industrial oxidation reactions in the gas phase, for instance the post-treatment of automotive exhaust gas. A peculiar mixed Ce-Zr (1:1) oxide, the ordered -Ce2Zr2O8 phase, is a promising catalytic material exhibiting an extraordinarily high oxygen storage capacity (OSC) and high thermal and chemical stability. We elucidated the temperature-dependent transformation between the pyrochlore pyr- Ce2Zr2O7.3 and -Ce2Zr2O8 phase upon oxygen uptake by in-situ X-ray diffraction, X-ray absorption and in-situ Raman spectroscopy, providing insights into the electronic and structural changes on the atomic level, which are at the heart of the extraordinarily high OSC. We demonstrate that the Ce3+ concentration can be followed during transformation in-situ by Raman spectroscopy of the electronic spin flip in the f-shell of Ce3+. The catalytic activity of the k-Ce2Zr2O8 phase has been investigated without an additional active component such as Pt: While the high OSC of the kappa phase is beneficial for the oxidation of CO, the oxidation of HCl turns out to be not affected by the high OSC.

storage capacity ; in-situ X-Ray diffraction ; in situ Raman spectroscopy ; Rietveld analysis

nije evidentirano