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

Denis A. Osinkin,Nina M. Bogdanovich,Andrey V. Fetisov,Natalia M. Porotnikova,Maxim V. Ananyev,Anna V. Khodimchuk

doi:10.3390/en13010250

Denis A. Osinkin, Nina M. Bogdanovich + Show 4 more

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https://doi.org/10.3390/en13010250

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Abstract

The oxygen surface kinetics of Sr2Fe1.5Mo0.5O6−δ was determined using the 16O2/18O2 isotope exchange method with gas phase analysis at 600–800 °C. The heterogeneous exchange rates (rH) and the oxygen diffusion coefficients (D) were calculated by processing the concentration dependences of the 18O fraction using Ezin’s model. The rates of oxygen dissociative adsorption (ra) and incorporation (ri) were calculated based on a model using the three exchange type rates. It has been established that the rates ra and ri 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 Sr2Fe1.5Mo0.5O6−δ is comparable to that of La0.6Sr0.4MnO3±δ oxide. High values of the oxygen diffusion coefficient were found for Sr2Fe1.5Mo0.5O6−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.

Highlights

One of the promising areas of development and creation of electrochemical devices is the search for materials with satisfactory physicochemical and electrochemical characteristics
The heterogeneous exchange rate, the oxygen diffusion coefficient, and the rates of oxygen dissociative adsorption and incorporation for Sr2 Fe1.5 Mo0.5 O6−δ were determined at the temperature range 600–800 ◦ C and the oxygen pressure 10−2 atm
It was shown that the oxygen exchange coefficient is 4 × 10−8 –4 × 10−7 cm s−1 at the temperature range 600–800 ◦ C and is comparable in value to the exchange rate of lanthanum-strontium manganite

Summary

Introduction

One of the promising areas of development and creation of electrochemical devices is the search for materials with satisfactory physicochemical and electrochemical characteristics. This includes the search for electrode materials for Solid-oxide fuel cells (SOFC). Sr2 Fe1.5 Mo0.5 O6−δ (SFM) oxide has been suggested as a promising material for electrochemical devices with symmetrical (i.e., with identical) electrodes [6,7] due to the high stability and electrical conductivity of SFM under oxidizing and reducing conditions [8,9,10,11,12,13,14,15,16,17,18,19]. The polarization resistance can be significantly reduced, by an order of magnitude, by doping crystal lattice, impregnating electrodes, or modifying the microstructure of electrodes [17,18,19,20,21,22,23,24,25,26]

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