Rate-Determining Steps of Oxygen Surface Exchange Kinetics on Sr2Fe1.5Mo0.5O6−δ

The oxygen surface kinetics of Sr 2 Fe 1.5 Mo 0.5 O 6−δ was determined using the 16 O 2 / 18 O 2 isotope exchange method with gas phase analysis at 600–800 °C. The heterogeneous exchange rates ( r H ) and the oxygen diffusion coefficients ( D ) were calculated by processing the concentration dependences of the 18 O fraction using Ezin’s model. The rates of oxygen dissociative adsorption ( r a ) and incorporation ( r i ) were calculated based on a model using the three exchange type rates. It has been established that the rates r a and r i were comparable in this temperature range. Assumptions were made about the effect of the chemical composition of the surface on the rate of oxygen adsorption. It was found that the oxygen exchange coefficient ( k ) of Sr 2 Fe 1.5 Mo 0.5 O 6−δ is comparable to that of La 0.6 Sr 0.4 MnO 3±δ oxide. High values of the oxygen diffusion coefficient were found for Sr 2 Fe 1.5 Mo 0.5 O 6−δ . The values were comparable to those of the double cobaltite praseodymium-barium and exceed by more than an order those of lanthanum-strontium manganite.