Surface strontium enrichment on highly active perovskites for oxygen electrocatalysis in solid oxide fuel cells

Ethan J. Crumlin; Eva Mutoro; Zhi Liu; Michael E. Grass; Michael D. Biegalski; Yueh-Lin Lee; Dane Morgan; Hans M. Christen; Hendrik Bluhm; Yang Shao-Horn

doi:10.1039/C2EE03397F

Surface strontium enrichment on highly active perovskites for oxygen electrocatalysis in solid oxidefuel cells†

Ethan J. Crumlin,‡^ac Eva Mutoro,‡^ac Zhi Liu,^d Michael E. Grass,^d Michael D. Biegalski,^e Yueh-Lin Lee,^f Dane Morgan,^f Hans M. Christen,^e Hendrik Bluhm^g and Yang Shao-Horn*^abc

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* Corresponding authors

^a Mechanical Engineering Department, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA, USA
E-mail: shaohorn@mit.edu

^b Materials Science and Engineering Department, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA, USA

^c Electrochemical Energy Laboratory, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA, USA

^d Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, USA

^e Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, USA

^f Department of Materials Science & Engineering, University of Wisconsin-Madison, 1509 University Avenue Madison, WI, USA

^g Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA

Abstract

Perovskite oxides have high catalytic activities for oxygen electrocatalysis competitive to platinum at elevated temperatures. However, little is known about the oxide surface chemistry that influences the activity near ambient oxygen partial pressures, which hampers the design of highly active catalysts for many clean-energy technologies such as solid oxide fuel cells. Using in situsynchrotron-based, ambient pressure X-ray photoelectron spectroscopy to study the surface chemistry changes, we show that the coverage of surface secondary phases on a (001)-oriented La_0.8Sr_0.2CoO_3−δ (LSC) film becomes smaller than that on an LSC powder pellet at elevated temperatures. In addition, strontium (Sr) in the perovskite structure enriches towards the film surface in contrast to the pellet having no detectable changes with increasing temperature. We propose that the ability to reduce surface secondary phases and develop Sr-enriched perovskite surfaces of the LSC film contributes to its enhanced activity for O₂ electrocatalysis relative to LSC powder-based electrodes.

Energy & Environmental Science

Surface strontium enrichment on highly active perovskites for oxygen electrocatalysis in solid oxidefuel cells†

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Surface strontium enrichment on highly active perovskites for oxygen electrocatalysis in solid oxide fuel cells

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