First principles calculations of oxygen reduction reaction at fuel cell cathodes

The efficiency of solid oxide fuel cells (SOFC) depends critically on materials, in particular for the cathode where the oxygen reduction reaction (ORR) occurs. Typically, mixed conducting perovskite ABO3-type materials are used for this purpose. The dominating surface terminations are (001) AO and...

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Bibliographic Details
Published in:Current opinion in electrochemistry 2020-02, Vol.19, p.122-128
Main Authors: Kotomin, Eugene A., Mastrikov, Yuri A., Merkle, Rotraut, Maier, Joachim
Format: Article
Language:English
Subjects:
Cathode materials
First principles calculations
Fuel cells
Oxygen reduction Reaction (ORR)
Perovskites
Polar surfaces
Rate determining step
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Summary:The efficiency of solid oxide fuel cells (SOFC) depends critically on materials, in particular for the cathode where the oxygen reduction reaction (ORR) occurs. Typically, mixed conducting perovskite ABO3-type materials are used for this purpose. The dominating surface terminations are (001) AO and BO2, with the relative fractions depending on materials composition and ambient conditions. Here, results of recent large-scale first principles (ab initio) calculations for the two alternative polar (La,Sr)O and MnO2 (001) terminations of (La,Sr)MnO3 cathode materials are discussed. The surface oxygen vacancy concentration for the (La,Sr)O termination is more than 5 orders of magnitude smaller compared to MnO2, which leads to drastically decreased estimated ORR rates. Thus, it is predicted for prototypical SOFC cathode materials that the BO2 termination largely determines the ORR kinetics, although with Sr surface segregation (long-term degradation) its fraction of the total surface area decreases, which slows down cathode kinetics.
ISSN:2451-9103
2451-9111
DOI:10.1016/j.coelec.2019.11.005