Nanostructured lanthanum cobaltate: Oxidation and coordination states of Co atoms

Abstract

Lanthanum cobaltate (LaCoOx) nanostructured inside the MCM-41 mesoporous molecular sieve as well as in the bulk LaCoO3 perovskite were characterised by SAXS, ESR, UV-vis DRS, EXAFS and XPS techniques. The nanosized LaCoOx particles stabilised within the mesopores of MCM-41 matrix containing Co atoms in rather low average oxidation state, which is not characteristic of bulk LaCoO3 perovskites. Meanwhile, the coordination states of Co in both cases are quite similar. Also, the concentration of Co(II) cations in cobaltate nanoparticles was found to be twice as in bulk LaCoO3 material. The supported cobaltate does not form short-range ordered species of LaCoO3 in the MCM-41 matrix but presents as the highly disordered, oxygen-deficient Co oxide nanophase which is probably to be stabilised by La ions present. © 2010 Taylor & Francis.