Synthesis of nano-crystalline La_(1-x)Sr_xCoO_(3-δ) perovskite oxides by EDTA-citrate complexing process and its catalytic activity for soot oxidation

摘要

In the present study, La_(1-x)Sr_xCoO_(3-δ) (x - 0.2,0.3,0.4,0.5) perovskite nano-particles have been successfully prepared by EDTA-citrate complexing process and the catalytic performance was examined for the soot oxidation activity. The physio-chemical properties of these materials were characterized by means of X-ray diffraction (XRD), thermogravimetry-differential thermal (TG-DTA) analysis, BET surface area and X-ray photoelectron spectroscopy (XPS) analysis, scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) analysis. TG-DTA analysis suggested that, in the temperature range of 350-500 °C, the pyrolysis of metalitrate/citrate/EDTA complexes takes place and the single phase La_(1-x)Sr_xCoO_(3-δ) perovskite oxides can be formed at 900°C and the phase formation has been confirmed by XRD analysis. The surface composition of the samples derived from XPS analysis indicated an impoverishment of lanthanum content at the surface with the increase of strontium content. For La_(0.6)Sr_(0.4)CoO_(3-δ) sample, Sr-enriched perovskite surface has been observed along with the more number of surface oxides (M(Sr, La, Co)—O) resulting in higher catalytic activity for soot oxidation than the others.