In - situ and in - operando studies of cobalt dop ed titanates by XRD, XAS and electrochemical impedance spectroscopy simulating working conditions as SOFC anodes and cathodes

NAPOLITANO, FEDERICO; SOLDATI, ANALIA L.; GECK, JOCHEN; GIEBELER, LARS; FERNANDEZ ZUVICH, AFRA; SALETA, MARTÍN; CANEIRO, ALBERTO; SERQUIS, ADRIANA C.; MOGNI, LILIANA V.

Campinas

Congreso; Reunión Anual de Usuarios LNLS; 2015

LNLS CNPEM

Perovskites with Ti on their B-site hasrecently been subject of study on the Solid Oxide Fuel Cell (SOFC) field sincethese materials presents good properties that enables their use as a possibleanode materials[1]. At the SOFC cathode side, the (La,Sr)CoO3 is one the moststudied cathode material [2]. In this work we present the study of theLa0.4Sr0.6(Ti,Co)O3 family (LSTC) for their use as electrode material for newdevices with symmetric designs (S-SOFC)[3,4]. In a first step, we completelycharacterized, for first time, their crystal and electronic structures at roomtemperature through X-ray diffraction and X-ray Absorption Spectroscopy. Thisstudy was followed by non-ambient experiments, simulating in-situ conditions asS-SOFC electrode (oxidizing and reducing atmospheres up to 750°C)[5-7].We found that cobalt doping increases theelectrical conductivity by 5 to 8 orders of magnitude under an oxidizingcondition respect to the undoped sample (La0.4Sr0.6TiO3-d), making thesematerials suitable to be used as cathodes but higher Co doping levels (x≤0.7)decrease the material stability as anode under reducing atmospheres. Besides,Co doping induces a slight rhombohedral distortion in the crystal symmetry atroom temperature, favoring a transformation to a cubic phase at highertemperatures (100-500°C, depending of the Co/Ti ratio).On the other hand, recent advances on materialscharacterization techniques have provided new platforms that enable the in-situstudy of crystallographic, mechanical, electronic, and electrochemicalproperties under a wide range of environmental conditions, not only forfundamental research but also in order to recreate a more realistic environmentin the case of applied research [8,11]. Here, we also present preliminaryresults on LSTC S-SOFC from our recently commissioned characterization device,capable to perform simultaneous XRD and Electrochemical Impedance Spectroscopymeasurements.