Stretching Epitaxial La_0.6Sr_0.4CoO_3–δ for Fast Oxygen Reduction

Journal Article · Tue Oct 31 00:00:00 EDT 2017 · Journal of Physical Chemistry. C

DOI:https://doi.org/10.1021/acs.jpcc.7b06374· OSTI ID:1414719

Lee, Dongkyu  ^[1]; Jacobs, Ryan ^[2]; Jee, Youngseok ^[3]; Seo, Ambrose ^[4]; Sohn, Changhee  ^[1]; Ievlev, Anton V.  ^[1]; Ovchinnikova, Olga S.  ^[1]; Huang, Kevin  ^[3]; Morgan, Dane  ^[2]; Lee, Ho Nyung  ^[1]

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1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
2. Univ. of Wisconsin - Madison, Madison, WI (United States)
3. Univ. of South Carolina, Columbia, SC (United States)
4. Univ. of Kentucky, Lexington, KY (United States)

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 La_0.6Sr_0.4CoO_3-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. Here, 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.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 1414719
• Journal Information: Journal of Physical Chemistry. C, Vol. 121, Issue 46; ISSN 1932-7447
• Publisher: American Chemical Society
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY