Catalytically active oxygen species in La1-xSrxCoO3-delta studied by XPS and XAFS spectroscopy

X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge struc ture (XANES) spectroscopy were used to characterize the oxygen species in p erovskite-type La1-xSrxCo3-delta with x = 0 and 0.2. The XPS method used sy nchrotron radiation with variable excitation energies. XPS showed two kinds of oxygen species: a surface species with a high binding energy and a bulk species with a low binding energy, Compared with LaCoO3, the surface oxyge n species in La0.8Sr0.2CoO3-delta was distributed into a deeper region, Com parison of the XANES spectra measured by partial photoelectron yield, total photoelectron yield, and fluorescence yield methods identified three featu res assigned to the surface species, which were identical to those of anion ic dioxygen. These results indicate that the partial replacement of La by S r causes the distribution of negatively charged dioxygen species to a deepe r region. We think that this anionic dioxygen species is related to the hig h oxidation activity of La0.8Sr0.2CoO3-delta.