A series of composite oxides were prepared by a modified citric method. These perovskite oxides were further modified with Ru through impregnation. X-ray diffraction, X-ray photoelectron spectroscopy (XPS) and temperature-programmed-reduction (TPR) techniques were adopted to investigate the properties of both the as-prepared perovskite oxides and the surface-Ru-modified samples. XPS results indicated the existence of ions in the fresh samples and transformed to after reduction. The hydrogen consumed by these perovskite oxides during TPR increased with the Sr doping, which was more than twice of the theoretical value according to Kröger-Vink notation. The reduction temperature of Cr ions of significantly decreased with an increase of the Ru loading. A small reduction peak at , which was not shifted by increasing Ru loadings, was observed and could be ascribed to the reduction of trace chromate phases. On all TPR profiles of the three doped perovskites with unity of the A-site and B-site ratio, the reduction of Ru species could not be observed at low Ru loadings (0.05% and 0.1%). A reduction peak from particles appeared at temperatures prior to the perovskite reduction on the TPR plots of modified and with high Ru loading (0.5% and 1%, respectively), but it did not occur with the Ru modified in the investigated Ru loading range. The TPR results of the Ru modified depicted that some Ru ions might be stabilized due to the incorporation into the oxide.
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.Copyright © 2007
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