Transport and electrochemical properties of Sr2Fe1.5Mo0.5O6 + Ce0.8Sm0.2O1.9 composite as promising anode for solid oxide fuel cells

Resumo

Study of the physical and electrical properties of the Sr₂Fe_1.5Mo_0.5 + Ce_0.8Sm_0.2O_1.9 composite material and its electrochemical properties as an electrode in contact with lanthanum gallate based electrolyte based on in reducing media revealed an increase in the dilatometric curve slope at around 400°C. This corresponds to an increase in the thermal expansion coefficient from 12.8 × 10^–6 to 19.3 × 10^–6 °C^–1. An analysis of electrochemical impedance spectra by the relaxation-time-distribution method demonstrated the electrode reaction is localized in the frequency range 500–0.01 Hz. The electrical conductivity of the material under study was found to be about 17 S cm^–1 at 800°C in the atmosphere of humid hydrogen. The polarization resistance under the same conditions was about 0.15 Ω cm². The dependence of the polarization resistance on the partial pressure of hydrogen is linear with a reaction order of about–0.4, whereas that on the partial pressure of water has the opposite slope with a reaction order of about 0.2.