Stretching Epitaxial La0.6Sr0.4CoO3-δ for Fast Oxygen Reduction

Dongkyu Lee, Ryan Jacobs, Youngseok Jee, Ambrose Seo, Changhee Sohn, Anton V. Ievlev, Olga S. Ovchinnikova, Kevin Huang, Dane Morgan, Ho Nyung Lee

Research output: Contribution to journalArticlepeer-review

42 Scopus citations

Abstract

The slow kinetics of the oxygen reduction reaction (ORR) is one of the key challenges in developing high performance energy devices, such as solid oxide fuel cells. Straining a film by growing on a lattice-mismatched substrate has been a conventional approach to enhance the ORR activity. However, due to the limited choice of electrolyte substrates to alter the degree of strain, a systematic study in various materials has been a challenge. Here, we explore the strain modulation of the ORR kinetics by growing epitaxial La0.6Sr0.4CoO3-δ (LSCO) films on yttria-stabilized zirconia substrates with the film thickness below and above the critical thickness for strain relaxation. Two orders of magnitude higher ORR kinetics is achieved in an ultrathin film with ∼0.8% tensile strain as compared to unstrained films. Time-of-flight secondary ion mass spectrometry depth profiling confirms that the Sr surface segregation is not responsible for the enhanced ORR in strained films. We attribute this enhancement of ORR kinetics to the increase in oxygen vacancy concentration in the tensile-strained LSCO film owing to the reduced activation barrier for oxygen surface exchange kinetics. Density functional theory calculations reveal an upshift of the oxygen 2p-band center relative to the Fermi level by tensile strain, indicating the origin of the enhanced ORR kinetics.

Original languageEnglish
Pages (from-to)25651-25658
Number of pages8
JournalJournal of Physical Chemistry C
Volume121
Issue number46
DOIs
StatePublished - Nov 22 2017

Bibliographical note

Publisher Copyright:
© 2017 American Chemical Society.

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • General Energy
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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