Catalytically Active Oxygen Species in La1-xSrxCoO3-δ Studied by XPS and XAFS Spectroscopy

X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge structure (XANES) spectroscopy were used to characterize the oxygen species in perovskite-type La 1 - x Sr x CoO 3 - δ with x = 0 and 0.2. The XPS method used synchrotron 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 LaCoO 3, the surface oxygen species in La 0.8 Sr 0.2 CoO 3 - δ was distributed into a deeper region. Comparison of the XANES spectra measured by partial photoelectron yield, total photoelectron yield, and fluorescence yield methods identified three features assigned to the surface species, which were identical to those of anionic dioxygen. These results indicate that the partial replacement of La by Sr causes the distribution of negatively charged dioxygen species to a deeper region. We think that this anionic dioxygen species is related to the high oxidation activity of La 0.8 Sr 0.2 CoO 3 - δ .