Due to the need for energy supply through cleaner and more efficient technologies, the interest for the water gas shift reaction (WGSR) has increased especially due to its role in purifying hydrogen-rich streams. In order to find alternative catalysts for this reaction, the effect of gadolinium and its amount on the properties of iron oxide-based catalysts was studied in this work. Samples with different gadolinium to iron molar ratio (0.05; 0.1 and 0.15) were prepared by sol-gel method and characterized by chemical analysis, thermogravimetry, differential scanning calorimetry, infrared spectroscopy, X-ray diffraction, Mössbauer spectroscopy, specific surface area measurements and thermoprogrammed reduction. The catalysts were evaluated in WGSR at 1 atm in the range of 250-400 • C. Hematite and gadolinium ferrite were detected for all fresh catalysts based on iron and gadolinium while magnetite and iron carbides and gadolinium oxide were found for the spent ones. The specific surface area increased due to gadolinium, related to its role as spacer. Gadolinium made the reduction of Fe 3+ and Fe 2+ species more difficult for all catalysts and then inhibited the production of iron carbides during reaction, increasing the activity. The catalyst with Gd/Fe = 0.10 showed the highest activity that was assigned to its highest specific surface area, which exposed more active sites. No methane or ethane was found indicating that the iron carbides were inactive to Fischer-Tropsch synthesis under reaction conditions.

Films of lanthanum strontium manganite, LSM (La 0.8 Sr 0.2 MnO 3 ) were deposited on yttria stabilized zirconia (YSZ) substrates by different methods aiming to establish the most suitable route to prepare cathodes for solid oxide fuel cells (SOFC). Samples were obtained by using a solution of lanthanum, strontium and manganese nitrates or a dispersion of the LSM powder in this solution. Both commercial and synthetized LSM powders were used, the last one obtained by amorphous citrate method. The films were deposited by spray pyrolysis on YSZ substrates prepared by uniaxial and isostatic pressing. Samples were characterized by scanning electron microscopy, confocal laser scanning microscopy, X-ray diffraction and two-probe conductivity measurements. The area specific resistance and relaxation to cathodic activation were measured by electrochemical impedance spectroscopy. The substrate obtained by uniaxial pressing and the commercial LSM produced films with the highest amount of surface cracks. The film obtained from the suspension showed area specific resistance and activation energy lower than the other produced from the solution. For both samples, the cathodic activation process resulted in an initial reduction of the total resistance of around 20%, the sample produced from the suspension being more resistant to relaxation. Therefore, the LSM suspension is more suitable than the salts solution for preparing films by spray pyrolysis on YSZ substrates to obtain efficient cathodes for SOFC.

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