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Molecular and Dissociative Adsorption of Oxygen on Solid Oxide Fuel Cell Cathode Materials of La1–xSrxCoO3, La1–xSrxCo1–yFeyO3, and La1–xSrxMnO3 Studied by Temperature-Programmed Desorption

ABSTRACT

Molecular and dissociative adsorption of oxygen on the surfaces of solid oxide fuel cell cathodes of La0.8Sr0.2CoO3, La0.6Sr0.4CoO3, La0.6Sr0.4Co0.2Fe0.8O3, and La0.8Sr0.2MnO3 were investigated using temperature-programmed desorption measurements for molecularly and atomically adsorbed oxygen. The desorption of molecularly adsorbed oxygen occurred at 140–150 K, and the adsorption sites for molecularly adsorbed oxygen were mostly oxygen vacancy sites that were formed by combinative desorption of surface oxygen atoms at 550–580 K. In the case of La1–xSrxCoO3, the recovery of oxygen vacancy sites required oxygen adsorption above 523 K, which indicates that the dissociative adsorption of oxygen at the oxygen vacancy sites was an activation process. Oxygen adsorption is the first step in the cathode reactions of fuel cells, and the oxygen adsorption properties of each cathode material are discussed with respect to the activity of the cathode.

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