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.

This work focuses on a La 0.6 Sr 0.4 Co 0.8 Fe 0.2 O 3-δ (LaSrCoFeO) perovskite and Fe 2 O 3 /LaSrCoFeO nanocomposite powders; the samples are characterized by means of X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), extended X-ray absorption fine structure (EXAFS), diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, scanning electronmicroscopy (SEM), and thermal analysis (TA) and inductively coupled plasma-atomic emission spectroscopy (ICP-AES). The nanosized LaSrCoFeO perovskite is obtained by Pechini method and is treated at increasing temperature. The LaSrCoFeO perovskite phase forms at T g 1173 K; at this temperature, traces of La 2 O 3 , Co 3 O 4 , and La (2-x) Sr x CoO 4 are also present. Strontium is surface segregated as SrCO 3 and SrO. Nanocomposite Fe 2 O 3 / LaSrCoFeO powder samples (Fe 2 O 3 /LaSrCoFeO ) 1:9 and 1:1 wt) are obtained by wet impregnation. The iron oxide deposition damages the perovskite structure because of the diffusion of iron inside the perovskite; this is particularly evident from SEM images.

No abstract