Dynamic oxygen mobility and a new insight into the role of Zr atoms in three-way catalysts of Pt/CeO2-ZrO2

The dynamic oxygen mobility and oxygen storage capacity (OSC) on three-model three-way catalysts of Pt/CeO2-ZrO2 (CZ-O, CZ-D and CZ-R) was characterized by the O-18/O-16 isotopic exchange (IE) reaction combined with CO oxidation. The measured oxygen surface and bulk diffusion coefficients, OSC, and oxygen release rates were correlated with XRD spectra, surface areas, metal dispersions and the other physical parameters. We found that the oxygen mobility was parallel to the structural homogeneity of Zr introduction into the CeO2 framework, decreasing as CZ-R > CZ-D > CZ-O. The oxygen diffusion coefficients over CeO2-ZrO2 oxides hinted us that oxygen species are mobile in the oxide support. In addition to the contribution to the space effect, we proposed a new insight to the role of zirconium atoms as carriers for the oxygen transfer, although further investigation is necessary. These results showed that the combined IE reaction could be counted as a reliable technique for qualifying the oxygen mobility, the OSC and oxygen release rates, and is expected to be a direct probe into the nature of CeO2-ZrO2 oxygen storage materials and further development of more efficient oxygen storage materials. (C) 2004 Elsevier B.V. All rights reserved.