Nano-structured Pd doped LaFe(Co)O3 perovskite; synthesis, characterization and catalytic behavior

Abstract

LaFexCo(1-x)O3 nanoparticles were prepared via a coprecipitation method and the effects of Pd dopant along with the type of alkaline agent on the powder particle characteristics have been studied. The catalytic activities of the synthesized perovskites for the CO and CH4 oxidation were also studied. X-ray diffraction (XRD) patterns confirmed the formation of a single-phase orthorhombic perovskite structure in the synthesized samples. Field emission scanning electron microscopy (FESEM) and BET analyses showed that using ammonia as the precipitant yields finer particles with higher specific surface areas for both un-doped and Pd-doped samples. FESEM micrographs also indicated that incorporation of Pd decreases the mean particle size of the perovskite powders. Raman spectroscopy results demonstrated that palladium occupies the B octahedral sites of the perovskite lattice. H2 temperature programmed reduction (H2-TPR) and O2 temperature programmed desorption (O2-TPD) results revealed that Pd-doping not only improves the reducibility of the iron and cobalt cations, but also boosts the number of mobile lattice oxygen species. Transmission electron microscopy (TEM) analysis confirmed formation of metallic Pd clusters having the size of 2–7 nm on the surface of Pd-doped perovskite under the reductive atmosphere. LaFe0.57Co0.38Pd0.05O3 sample co-precipitated by NH4OH enjoys the highest catalytic activity for both CO and CH4 oxidation.