Rational Development of IT-SOFC Electrodes Based on the Nanofunctionalization of La_0.6Sr_0.4Ga_0.3Fe_0.7O₃ with Oxides. Part 2: Anodes by Means of Manganite Oxide

Abstract

To promote the diffusion on the market of solid oxide fuel cell (SOFC) devices, the use of fuels other than the most appealing hydrogen and also decreasing the working temperature could show the way forward. In the first part, we concentrated our efforts on cathodes; hereby, we focused on anodes and concentrated our efforts to develop a sustainable multifuel anode. We decided to develop LSGF (La 0.6 Sr 0.4 Ga 0.3 Fe 0.7 O 3 )-based nanocomposites by depositing manganite oxide to enhance the performance toward propane. MnO x has been deposited by a wet impregnation method, and the powders have been largely characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray analysis, X-ray photoelectron spectroscopy, hydrogen temperature-programmed reduction, oxygen temperature-programmed desorption, and N 2 adsorption. Cell performances were first collected in hydrogen as a function of both the temperature and hydrogen content. EIS measurements were studied using Nyquist and Bode plots, and they show two processes at high frequency, assigned to charge transfer at the electrode/electrolyte interface, and at low frequency due to the dissociative adsorption of hydrogen. The Arrhenius plot of area specific resistance suggests two different trends, and the activation energy decreases from 117 kJ/mol at 750 °C to 46 kJ/mol above that temperature. This behavior is often connected to chemical modification of the catalyst or changes in the limiting step processes. Power densities in hydrogen and propane were determined at 744 °C after 1 h of operation, achieving 70 mW/cm 2 in H 2 and 67 mW/cm 2 in C 3 H 8 . The open-circuit voltage increases from 1.10 V in hydrogen to 1.13 V in propane.