Abstract
The mechanism of interaction between gaseous oxygen and the Sr1.95Fe1.4Ni0.1Mo0.5O6–δ promising material for cathodes of SOFC has been investigated by two isotopic methods: the pulse isotope exchange and the oxygen isotope exchange with the gas phase analysis, making it possible to obtain and compare the kinetic parameters under equilibrium conditions and the mixture gas carrier flow under the sample, which extends understanding of processes and makes experimental conditions of the second case closer to real operating conditions of electrode material. The time dependences of changes in 16O2, 16O18O and 18O2 over the sample allowed us to calculate the concentration of 18O labeled oxygen (α) at the temperatures ranging from 300 to 800 °C. The oxygen exchange rate (rH, atom/(cm2 × s)), the oxygen diffusion coefficient (D, cm2/s), the corresponding rates of elementary processes of dissociative adsorption (ra, atom/(cm2 × s)) and oxygen incorporation in the lattice (ri, atom/(cm2 × s)) are calculated. The results of two independent isotopic methods were analyzed and revealed a good agreement of the obtained data. The effect of modifying Sr2Fe1.5Mo0.5O6–δ by introducing deficiency in the Sr-sublattice and Ni-doping in the Fe-sublattice on the kinetic parameters is discussed.
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