Anomalous Interface and Surface Strontium Segregation in (La1-ySry)2CoO4±δ/La1-xSrxCoO3-δ Heterostructured Thin Films

Zhenxing Feng; Yizhak Yacoby; Milind J Gadre; Yueh-Lin Lee; Wesley T Hong; Hua Zhou; Michael D Biegalski; Hans M Christen; Stuart B Adler; Dane Morgan; Yang Shao-Horn

doi:10.1021/jz500293d

Anomalous Interface and Surface Strontium Segregation in (La1-ySry)2CoO4±δ/La1-xSrxCoO3-δ Heterostructured Thin Films

J Phys Chem Lett. 2014 Mar 20;5(6):1027-34. doi: 10.1021/jz500293d. Epub 2014 Mar 7.

Authors

Zhenxing Feng, Yizhak Yacoby¹, Milind J Gadre², Yueh-Lin Lee², Wesley T Hong, Hua Zhou³, Michael D Biegalski⁴, Hans M Christen⁴, Stuart B Adler⁵, Dane Morgan², Yang Shao-Horn

Affiliations

¹ ∥Racah Institute of Physics, Hebrew University, Jerusalem 91904, Israel.
² ▽Department of Materials Science and Engineering, University of Wisconsin-Madison, 1509 University Avenue, Madison, Wisconsin 53706, United States.
³ ⊥Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, United States.
⁴ #Center for Nanophase Materials Science, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831, United States.
⁵ ○Department of Chemical Engineering, University of Washington, 105 Benson Hall, Seattle, Washington 98195, United States.

PMID: 26270983
DOI: 10.1021/jz500293d

Abstract

Heterostructured oxides have shown unusual electrochemical properties including enhanced catalytic activity, ion transport, and stability. In particular, it has been shown recently that the activity of oxygen electrocatalysis on the Ruddlesden-Popper/perovskite (La1-ySry)2CoO4±δ/La1-xSrxCoO3-δ heterostructure is remarkably enhanced relative to the Ruddlesden-Popper and perovskite constituents. Here we report the first atomic-scale structure and composition of (La1-ySry)2CoO4±δ/La1-xSrxCoO3-δ grown on SrTiO3. We observe anomalous strontium segregation from the perovskite to the interface and the Ruddlesden-Popper phase using direct X-ray methods as well as with ab initio calculations. Such Sr segregation occurred during the film growth, and no significant changes were found upon subsequent annealing in O2. Our findings provide insights into the design of highly active catalysts for oxygen electrocatalysis.

Keywords: ab initio calculation; coherent Bragg rod analysis; fuel cell; heterostructure perovskites; oxides; strontium segregation; surface and interface.