In Situ Ambient Pressure X-ray Photoelectron Spectroscopy of Cobalt Perovskite Surfaces under Cathodic Polarization at High Temperatures

Ethan J. Crumlin, Eva Mutoro, Wesley T. Hong, Michael D. Biegalski, Hans M. Christen, Zhi Liu, Hendrik Bluhm, Yang Shao-Horn

Research output: Contribution to journalArticlepeer-review

58 Scopus citations

Abstract

Heterostructured oxide interfaces have demonstrated enhanced oxygen reduction reaction rates at elevated temperatures (∼500-800 C); however, the physical origin underlying this enhancement is not well understood. By using synchrotron-based in situ ambient pressure X-ray photoelectron spectroscopy (APXPS), we focus on understanding the surface electronic structure, elemental composition, and chemical nature of epitaxial La0.8Sr 0.2CoO3-δ (LSC113), (La 0.5Sr0.5)2CoO4±δ (LSC214), and LSC214-decorated LSC113 (LSC 113/214) thin films as a function of applied electrical potentials (0 to -800 mV) at 520 C and p(O2) of 1 × 10-3 atm. Shifts in the top of the valence band binding energy and changes in the Sr 3d and O 1s spectral components under applied bias reveal key differences among the film chemistries, most notably in the degree of Sr segregation to the surface and quantity of active oxygen sites in the perovskite termination layer. These differences help to identify important factors governing the enhanced activity of oxygen electrocatalysis observed for the LSC113/214 heterostructured surface. © 2013 American Chemical Society.
Original languageEnglish (US)
Pages (from-to)16087-16094
Number of pages8
JournalThe Journal of Physical Chemistry C
Volume117
Issue number31
DOIs
StatePublished - Jul 29 2013
Externally publishedYes

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