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Bulk Properties of the Oxygen Reduction Catalyst SrCo_(0.9)Nb_(0.1)O_(3-δ)

Usiskin, Robert E. and Davenport, Timothy C. and Wang, Richard Y. and Guan, Webster and Haile, Sossina M. (2016) Bulk Properties of the Oxygen Reduction Catalyst SrCo_(0.9)Nb_(0.1)O_(3-δ). Chemistry of Materials, 28 (8). pp. 2599-2608. ISSN 0897-4756. doi:10.1021/acs.chemmater.5b04783.

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The perovskite SrCo_(0.9)Nb_(0.1)O_(3−δ) (SCN) has excellent electrochemical activity toward oxygen reduction, and it is also valuable as a possible model material for other state-of-the-art perovskite catalysts based on strontium and cobalt, such as Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3−δ) (BSCF). Here we report thermogravimetric, conductivity, and diffraction measurements from SCN. We find that the thermodynamic stability limits of SCN are slightly more favorable than those reported for BSCF, although both materials exhibit a slow oxidative partial decomposition under likely operating conditions. In SCN, this decomposition is thermodynamically preferred when the average formal oxidation state of cobalt is greater than ∼3.0+, but due to sluggish kinetics, metastable SCN with higher cobalt valence can be observed. The oxygen stoichiometry 3−δ varies from 2.45 to 2.70 under the conditions studied, 500–1000 °C and 10^(–4)–1 bar O_2, which encompass both stable and metastable behavior. The electronic conductivity is p-type and thermally activated, with a value at 600 °C in air of 250 S cm^(–1), comparable to that of La_(0.8)Sr_(0.2)MnO_(3−δ). The polaron migration enthalpy decreases linearly from 0.30 to 0.05 eV as 3−δ increases from 2.52 to 2.64. Thermal and chemical expansivities are also reported.

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Haile, Sossina M.0000-0002-5293-6252
Alternate Title:Bulk Properties of the Oxygen Reduction Catalyst SrCo0.9Nb0.1O3-δ
Additional Information:© 2016 American Chemical Society. Received: December 10, 2015; Revised: March 31, 2016; Publication Date (Web): April 01, 2016. This work was funded by the National Science Foundation (Award No. DMR-0918224), the California Institute of Technology Summer Undergraduate Research Fellowship program (to R.W. and W.G.), and an EERE Postdoctoral Research Award (to T.C.D.). (Opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.) The authors declare no competing financial interest.
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Caltech Summer Undergraduate Research Fellowship (SURF)UNSPECIFIED
Department of Energy (DOE)UNSPECIFIED
Issue or Number:8
Record Number:CaltechAUTHORS:20160418-135451492
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Official Citation:Bulk Properties of the Oxygen Reduction Catalyst SrCo0.9Nb0.1O3−δ Robert E. Usiskin, Timothy C. Davenport, Richard Y. Wang, Webster Guan, and Sossina M. Haile Chemistry of Materials 2016 28 (8), 2599-2608 DOI: 10.1021/acs.chemmater.5b04783
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:66253
Deposited By: Tony Diaz
Deposited On:18 Apr 2016 22:12
Last Modified:10 Nov 2021 23:55

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