The electrochemical behavior of the promising Sr2Fe1.5Mo0.5O6-δ + Ce0.8Sm0.2O1.9-δ anode for the intermediate temperature solid oxide fuel cells

A promising Sr2Fe1.5Mo0.5O6-δ + Ce0.8Sm0.2O1.9-δ IT-SOFC anode material in contact with the lanthanum gallate based electrolyte in H2+H2O + Ar gas mixtures was studied. The anode has the polarization resistance nearly 0.3 Ω cm2 at 700 °C that is considered as the acceptable value for the practical application in IT-SOFC. The distribution of relaxation time curves showed that the electrode reaction was limited by two rate-determining steps within the frequencies range 10-0.01 Hz. The opposite behavior of the polarization resistance vs. water and hydrogen partial pressure was founded. This behavior was explained by the low electrochemical activity of the anode to the water dehydrogenation. The additive of nickel into the anode resulted in the reduction of the polarization resistance and increase the rate of the water dehydrogenation. A long-term test carried out during 500 h at 700°С in a humid hydrogen demonstrated the exponential behavior of the polarization resistance. The weight decrease of about 4.5% for Sr2Fe1.5Mo0.5O6-δ powder in Ar + 5%H2 at 700 °C within the 300 h the exposure was observed.