期刊
CHEMISTRY OF MATERIALS
卷 22, 期 1, 页码 70-76出版社
AMER CHEMICAL SOC
DOI: 10.1021/cm9021563
关键词
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资金
- Academy of Finland [110433, 126528]
- Tekes [1726/31/07]
- Emil Aaltonen Foundation
- Academy of Finland (AKA) [110433, 110433] Funding Source: Academy of Finland (AKA)
Evolution of the O-K and Co-L edge XANES spectra for SrCoO3-delta upon increasing oxygen content from 2.50 to 2.82 reveals that superoxide (O-2(-)) related features are overwhelmingly strong in the surface region of highly oxygen-deficient samples. Moreover, should it be always present in the bulk, octahedrally coordinated cobalt is unobservable in the surface region of highly oxygen-deficient samples. On the other hand, the surface region hosts square-pyramidally coordinated cobalt even in brownmillerite SrCoO2.50, Observations in the present work support an oxygen-intercalation mechanism in which (i) O-2 is first absorbed on the surface as O-2(-), (ii) then reductively split into Ox- associated with square-pyramidally coordinated cobalt, and (iii) finally in the bulk eventually reoxidized to Oz- (0 < z < x) being attached to octahedrally coordinated cobalt. The fact that only minute chemical shifts of the Co-L edge branches are seen indicates that electron transfer mostly takes place between oxygen atoms.
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