Abstract: 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 O2 atmosphere at 120 °C restores the virgin surfaces.
Keywords: catalysis; oxygen evolution; manganese perovskite; Pr1−xCaxMnO3; XANES; XPS; Mn L-edge; active state; oxygen vacancies; surface valence
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Mierwaldt, D.; Mildner, S.; Arrigo, R.; Knop-Gericke, A.; Franke, E.; Blumenstein, A.; Hoffmann, J.; Jooss, C. In Situ XANES/XPS Investigation of Doped Manganese Perovskite Catalysts. Catalysts 2014, 4, 129-145.
Mierwaldt D, Mildner S, Arrigo R, Knop-Gericke A, Franke E, Blumenstein A, Hoffmann J, Jooss C. In Situ XANES/XPS Investigation of Doped Manganese Perovskite Catalysts. Catalysts. 2014; 4(2):129-145.
Mierwaldt, Daniel; Mildner, Stephanie; Arrigo, Rosa; Knop-Gericke, Axel; Franke, Emanuel; Blumenstein, Andreas; Hoffmann, Jörg; Jooss, Christian. 2014. "In Situ XANES/XPS Investigation of Doped Manganese Perovskite Catalysts." Catalysts 4, no. 2: 129-145.