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

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• 作者：Ethan J. Crumlin ; Eva Mutoro ; Wesley T. Hong ; Michael D. Biegalski ; Hans M. Christen ; Zhi Liu ; Hendrik Bluhm ; Yang Shao-Horn
• 刊名：The Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：August 8, 2013
• 年：2013
• 卷：117
• 期：31
• 页码：16087-16094
• 全文大小：617K
• 年卷期：v.117,no.31(August 8, 2013)
• ISSN：1932-7455

文摘

Heterostructured oxide interfaces have demonstrated enhanced oxygen reduction reaction rates at elevated temperatures (500鈥?00 掳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 La_0.8Sr_0.2CoO_{3鈭捨?/sub> (LSC113), (La0.5Sr0.5)2CoO4卤未 (LSC214), and LSC214-decorated LSC113 (LSC113/214) thin films as a function of applied electrical potentials (0 to 鈭?00 mV) at 520 掳C and p(O2) of 1 脳 10^鈥? 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.}