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Structural and chemical reactivity modifications of a cobalt perovskite induced by Sr-substitution. An in situ XAS study

AutorHueso, José L. ; Holgado, Juan P. ; Pereñíguez, Rosa ; González-Delacruz, V.M. ; Caballero, Alfonso
Palabras claveChemical techniques
Crystal structure
IInorganic compounds
XAFS (EXAFS and XANES)
Fecha de publicación2015
EditorElsevier
CitaciónMaterials Chemistry and Physics, 151:21-33 (2015)
ResumenLaCoO3 and La0.5Sr0.5CoO3-δ perovskites have been studied by in situ Co K-edge XAS. Although the partial substitution of La(III) by Sr(II) species induces an important increase in the catalytic oxidation activity and modifies the electronic state of the perovskite, no changes could be detected in the oxidation state of cobalt atoms. So, maintaining the electroneutrality of the perovskite requires the generation of oxygen vacancies in the network. The presence of these vacancies explains that the substituted perovskite is now much more reducible than the original LaCoO3 perovskite. As detected by in situ XAS, after a consecutive reduction and oxidation treatment, the original crystalline structure of the LaCoO3 perovskite is maintained, although in a more disordered state, which is not the case for the Sr doped perovskite. So, the La0.5Sr0.5CoO3-δ perovskite submitted to the same hydrogen reduction treatment produces metallic cobalt, while as determined by in situ XAS spectroscopy the subsequent oxidation treatment yields a Co(III) oxide phase with spinel structure. Surprisingly, no Co(II) species are detected in this new spinel phase.
Versión del editorhttp://dx.doi.org/ 10.1016/j.matchemphys.2014.11.015
URIhttp://hdl.handle.net/10261/114216
DOI10.1016/j.matchemphys.2014.11.015
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