Journal
CATALYSTS
Volume 4, Issue 2, Pages 129-145Publisher
MDPI
DOI: 10.3390/catal4020129
Keywords
catalysis; oxygen evolution; manganese perovskite; Pr1-xCaxMnO3; XANES; XPS; Mn L-edge; active state; oxygen vacancies; surface valence
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Funding
- Deutsche Forschungsgemeinschaft through the CRC 1073 [C02]
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Studying catalysts in situ is of high interest for understanding their surface structure and electronic states in operation. Herein, we present a study of epitaxial manganite perovskite thin films (Pr1-xCaxMnO3) active for the oxygen evolution reaction (OER) from electro-catalytic water splitting. X-ray absorption near-edge spectroscopy (XANES) at the Mn L- and O K-edges, as well as X-ray photoemission spectroscopy (XPS) of the O 1s and Ca 2p states have been performed in ultra-high vacuum and in water vapor under positive applied bias at room temperature. It is shown that under the oxidizing conditions of the OER a reduced Mn2+ species is generated at the catalyst surface. The Mn valence shift is accompanied by the formation of surface oxygen vacancies. Annealing of the catalysts in O-2 atmosphere at 120 degrees C restores the virgin surfaces.
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