J.L. Hueso, A. Caballero, M. Ocaña, A.R. González-Elipe
Journal of Catalysis, 257 (2008) 334-344
doi: 10.1016/j.jcat.2008.05.012

This work reports on the reactivity toward carbon of a La_0.5Sr_0.5CoO_3−δ perovskite prepared by spray pyrolysis. It is shown that this perovskite presents a moderate activity for the thermal oxidation of carbon, producing a decrease in its temperature of combustion of ca. 150 °C and a significant increase in the selectivity toward CO₂. Different experiments were carried out with electron energy loss spectroscopy (EELS) and X-ray photoemission spectroscopy (XPS) for the perovskite and its physical mixture with a high-surface area carbon material. In the physical mixture, the cobalt at the surface was partially reduced to Co²⁺ even at room temperature. XPS demonstrated a species of oxygen with low electron density at the catalyst surface. This species seemed to play a significant role in the oxidation processes at the perovskite surface. A model is proposed to account for the changes exhibited by the catalyst during its reaction with carbon.