Synthesis and characterization of La0.6Sr0.4Co1-yFeyO3 nanorods

A. E. MEJÍA GÓMEZ; J. SACANELL; A. L. SOLDATI; C. RAMOS; S.J.A. FIGUEROA ; M.C.A. FANTINI; A.F. CRAIEVICH; D.G. LAMAS

San Pablo

Congreso; 22nd Meeting of the Brazilian Crystallographic Association and 1st Meeting of the Latin American Crystallographic Association; 2015

Asociación Brasilera de Cristalografía y Asociación Latinoamericana de Cristalografía

Fuel cells are one of the most promising devices for environmentally clean energy production by directly converting chemical energy into electricity. Among them, solid oxide fuel cells (SOFCs) have the unique capability to use different fuels such as hydrocarbons or hydrogen. However, several issues have to be solved in order to improve their efficiency and reduce their costs. The reduction of their working temperature, which is typically around 900-1000°C, is one of the most important issues. For this reason, extensive research has been devoted to develop novel materials for intermediate temperature SOFCs (IT-SOFCs). In the case of the cathode, one step in this direction is the use of mixed ionic and electronic conductors (MIECs), which exhibit higher performance than conventional electronic conductors. In particular, La0.6Sr0.4Co1-yFeyO3 perovskites have shown excellent electrocatalytic properties for the oxygen reduction reaction.In the last years, extensive research has been devoted to study the structural and electrochemical properties of nanostructured MIECs as cathodes for IT-SOFCs. Nanomaterials are not employed in conventional SOFCs since grain growth is expected to occur at the high operation temperatures of these devices. However, their use in IT-SOFCs is currently under evaluation. Cathodes based on nanostructured MIECs are very interesting because the number of active sites for the oxygen reduction reaction is expected to increase dramatically.In this work, we report the synthesis and characterization of La0.6Sr0.4Co1-yFeyO3 nanorods (y = 0.2; 0.5 and 0.8). These nanomaterials were synthesized by a pore-wetting technique starting from a nitrate solution of the desired cations and using polycarbonate porous membranes of average pore size of 200 nm as templates. The characterization was performed by synchrotron X-ray powder diffraction (SXPD), scanning electron microscopy, X-ray absorption near edge structure (XANES) spectroscopy and Mössbauer spectroscopy. SXPD analysis confirmed that single-phase samples exhibiting the rhombohedral phase (R3cspace group) can be obtained after calcination at 1000°C for 1 h. The average crystallite size was about 30 nm for all compositions. SEM observations confirmed the rod-like nanostructure of the samples. The rods exhibited typical lengths of about 0.8-1 m and were formed by nanoparticles with diameters of about 140-150 nm. Finally, XANES and Mössbauer spectroscopies allowed the study of the oxidation states of Co and Fe in the series.