La0.6Sr0.4Co1−y FeyO3−δ (y = 0.2, 0.5, 0.8) perovskite-type oxide powders were prepared by the citrate gel method with the aim of investigating the influence of cobalt/iron atomic ratio on the chemical and structural properties as well as on the catalytic activity. The samples were characterized by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermal analysis, Kr physisorption surface area, scanning electron microscopy (SEM), and temperature programmed reduction (TPR). XRD outcomes reveal the formation of perovskite phase after calcination at 873 K. Depending on the Co/Fe atomic ratio, the perovskite exhibits two different structure: rhombohedral for y < 0.5, orthorhombic for y ≥ 0.5. However, other phases are also observed. The crystallite size increases with the calcination temperature, while decreases with the iron content. The specific surface area of the La0.6Sr0.4Co1−y FeyO3-δ perovskites (calcined at 1073 K) is low, but increases with the iron amount: it varies between 4.1 and 6.6 m2 g−1 moving from y = 0.2 to y = 0.8. XPS results reveal the presence of traces of Co(II) in the sample with lower cobalt amount. The scanning electron micrographs reveal nanoscaled near spherical particles which are clustered together, forming a highly porous microstructure. However, the samples with higher iron content show a more compact morphology due to the enhanced agglomeration. The perovskite phase is rather stable even after aggressive treatment as high temperature reduction. The influence of cobalt/iron atomic ratio on the catalytic activity toward alcohol steam reforming was investigated. All the samples present good alcohol dehydrogenation activity, as resulting from the methanol steam reforming experiments. In the steam reforming of ethanol, the La0.6Sr0.4Co0.5Fe0.5O3-δ presents the better performance (especially after reduction at 873 K) with the complete conversion of ethanol into syngas above 850 K and the almost complete suppression of the ethylene formation at lower temperature. The differences of the activity toward ethanol steam reforming are attributable to a different stabilization of Co(0) nanoparticles produced during the reduction at 873 K.
A CuO/La0.6Sr0.4Co0.2Fe0.8O3-δ supported system was obtained by depositing, by wet impregnation, 10 wt% CuO loading on the La0.6Sr0.4Co0.2Fe0.8O3-δ surface. The surface properties are investigated by means of XPS. Besides the wide scan spectrum, detailed spectra for the La 3d, Sr 3d, Co 2p, Fe 2p, Cu 2p, O 1s, and C 1s regions, and related data, are presented and discussed.
In recent years, the growing interest in hydrogen energy has caused particularly large demand for catalysts used in the production of hydrogen and hydrogen-containing gases by the conversion of natural hydrocarbons. Perovskite oxides having the general formula of ABO3, where B usually designates a transition metal cation surrounded by six oxygen ions in octahedral coordination, and A is a cation of rare-earth metal coordinated by 12 oxygen ions are very promising for this application. The present work focuses on the XPS analysis of a new perovskite material: La0.6Sr0.4Fe0.6Co0.2Cu0.2O3-δ powder. This powder was obtained by citrate gel process. The surface proprieties are investigated by means of XPS. Besides the wide scan spectrum, detailed spectra for the La 3d, Sr 3d, Fe 2p, Co 2p, Cu 2p, Cu LMM, O 1s and C 1s regions and related data are presented and discussed.
Perovskite-type oxides, ABO3, are known to be very good oxidation catalysts. The redox properties of the B cation, the availability of weakly bonded oxygen at the surface and the presence of lattice defects have been often claimed as responsible for their catalytic activity. Moreover, their performances can be improved if they are nanodimensioned. The present study focuses on the development of new LaCoO3-based catalysts for alcohol (such as methanol, ethanol) steam reforming. Several La0.6Sr0.4Co1-yFeyO3-δ (y=0.2, 0.5, 0.8) were prepared by the citrate gel method and calcined at 1073 K for 5 h in air. Herein, the influence of the cobalt/iron ratio on the surface properties was investigated.
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