Effects of preparation methods on the oxygen nonstoichiometry, B-site cation valences and catalytic efficiency of perovskite La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3-delta)

摘要

La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3-delta){ (LSCF) powders were synthesized respectively by an EDTA (ethylenediaminetetraacetic acid)-Citrate sol-gel process and a low-temperature auto-combustion process. The samples were characterized by XRD, SEM, BET, TGA and instant temperature analysis. The iodometric titration was used to determine the average valence of Co and Fe ions and the oxygen nonstoichiometry of the prepare powders. The catalytic properties of the synthesized powders were investigated by the hydrogen peroxide catalytic decomposition. Pure-perovskite structure was formed by both synthesis methods. The oxygen nonstoichiometry of the samples prepared by the auto-combustion process is larger than that by the sol-gel process. The catalytic activities of the powders from two synthesis processes also differed largely due to the different oxygen nonstoichiometry, surface area and crystalline sizes.