Study of La0.1Sr0.9TiO3 electrochemical response as anode for SOFC and its relation with microstructure

Abstract

La0.1Sr0.9TiO3 (LST) perovskite has been studied as anode material for Intermediate Temperature Solid Oxide Fuel Cell (IT-SOFC) applications. LST powders were synthesized by two chemical methods, one employed hexamethylenetetramine (HMTA) as a complexing agent while the other utilized ethylenediaminetetraacetic acid (EDTA). These approaches yielded different microstructures as evidenced by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and N2 adsorption/desorption isotherms studies. The effect of the microstructure on the electrochemical behavior of the obtained electrodes was studied by Electrochemical Impedance Spectroscopy (EIS) by varying the hydrogen partial pressure and the temperature. In addition, the evolution of specific area resistance with the hydrogen partial pressure allowed the identification of the reaction mechanism. The results of EIS were studied by electrical equivalent circuit (EEC) and distribution of relaxation times (DRT). The results suggest that the hydrogen oxidation reaction (HOR) limiting step for both samples is controlled by hydrogen dissociative-adsorption at the surface. The hydrogen adsorption is faster at the electrode formed by smaller nanoparticles, in which the activation energy decreases and the rate coefficient changes.