Structures and properties of La_0.8Sr_0.2MnO_3+σ-z SBA-15 (z=0, 1, 2, 4) perovskite catalysts

Abstract

Mesoporous La_0.8Sr_0.2MnO_3+σ/z SBA-15 (z = 1, 2, 4) perovskite oxides were synthesized via hard-templating with ordered mesoporous silica SBA-15 as the template. The as-prepared samples were characterized by XRD, SEM, AFM, BET, and XPS and the catalytic activity was tested for CO oxidation. The wide-angle XRD patterns showed that La_0.8Sr_0.2MnO_3+σ perovskite was formed. The SEM and AFM analyses exhibited that La_0.8Sr_0.2MnO_3+σ by hard-templating method had much smaller particle size (18 nm) than that (40 nm) by the sol-gel method. The perovskite-type oxides La_0.8Sr_0.2MnO_3+σ/z SBA-15 (z = 1, 2, 4) also displayed a higher BET surface area from 70 to 143.7 m²/g and a disordered mesostructure from nitrogen sorption analysis, as well as a small-angle XRD pattern. Moreover, the La_0.8Sr_0.2MnO_3+σ/z SBA-15 (z = 1, 2, 4) perovskite exhibited a much higher activity in CO oxidation than the conventional La_0.8Sr_0.2MnO_3+σ perovskite. Further analysis by the means of XPS techniques indicated that the existence of high content of O_ads/O_latt species contributed to the high activity.

Keywords

hard-templating / sol-gel / perovskite catalyst / mesoporous structure / CO oxidation

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