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Journal of nanoscience and nanotechnology

Kinetics investigation of oxygen storage capacity in La2O3-CeO2 solid solution.


PMID 21449363

Abstract

La2O3-CeO2 nanopowders with different La2O3 (0-20 mol%) were prepared by the sol-gel method. The modification of the cubic structure of ceria by substituting La3+ for Ce4+ into the lattice of CeO2 has been investigated. The crystal structure of La2O3-CeO2 nanomaterials has been examined by X-ray powder diffraction and analyzed by the Rietveld refinement method. The introduction of La3+ enlarges the octahedral void of unit cell in the cubic CeO2, which favors the oxygen migration in the crystal lattice. Raman characterization results show that the wavenumber of the La2O3-CeO2 solid solution shifted to red and the oxygen vacancy increased with lanthana content in Ce(1-x)La(x)O(2-x/2). The oxygen vacancy, generated by La3+ substituting for Ce4+, could supply more channels for oxygen migration through the lattice. The changes of lattice structure and the oxygen vacancy with La2O3 are correspondence with the results of oxygen storage capacity (OSC) measurement, which indicate that the changes of macro-performance are connected with the microstructure deformation of La2O3-CeO2. The kinetics of Ce0.9La0.2O1.9 nanomaterials with the highest OSC value was studied and the apparent activation energy (E(a)) of reduction and oxidation process was calculated to be 5.6 and 6.0 kJ/mol, respectively. The low E(a) value might be one of the reasons for Ce0.8La0.2O1.9 nanomaterials with the high OSC value.