Preparation and characterization of Pd loaded Sr-deficient K₂NiF₄-type (La, Sr)₂MnO₄ catalysts for NO-CO reaction

Pd-loaded K₂NiF₄-type perovskite oxides, Pd/La_0.2Sr_1.8-xMnO₄ were prepared by liquid-phase adsorption process, and their structural and catalytic properties were investigated. Pd deposition was carried out by mixing La_0.2Sr_1.8MnO₄ with Pd(NO₃)₂ in aqueous solution, followed by filtration, drying, and calcination at 800 °C. During the Pd deposition process, 5% of Sr in La_0.2Sr_1.8MnO₄ oxides was dissolved into the aqueous phase, whereas the perovskite structure retained. The content of Pd loaded on La_0.2Sr_1.8MnO₄ was 0.24 wt%. X-ray absorption spectroscopy studies showed that highly dispersed PdO nanoparticles were supported on Pd/La_0.2Sr_1.8MnO₄ prepared by the liquid-phase adsorption process, whereas aggregated PdO particles were formed on Pd/La_0.2Sr_1.8MnO₄ prepared by an impregnation method. The Pd/La_0.2Sr_1.8MnO₄ catalyst prepared by the liquid-phase adsorption process exhibited higher catalytic activity for NO-CO reaction than the 0.24 wt% Pd/La_0.2Sr_1.8MnO₄ catalyst prepared by the impregnation method.