Effect of praseodymium substitution on La1-xPrxMnO3 (x=0–0.4) perovskites and catalytic activity for NO oxidation

Abstract

La1-xPrxMnO3(x = 0, 0.05, 0.1, …, 0.4) perovskites were prepared readily via citric acid sol–gel method in the present study. Several characterization techniques have been employed, such as X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), Brunauer-Emmett-Teller (BET), N2 adsorption–desorption analyses, Oxygen temperature-programmed desorption (O2-TPD), Hydrogen temperature-programmed reduction (H2-TPR) and NO temperature-programmed desorption (NO-TPD), with the aim of exploring the effects of Pr substitution. Then the samples were submitted to activity test in catalytic NO oxidation. NO conversion was improved with the increase of Pr substitution when x ≤ 0.2, and then decreased with further addition of Pr. The most excellent catalytic activity with NO conversion of 91% at 260 °C was observed on La0.8Pr0.2MnO3. It was revealed that the appropriate Pr addition (x ≤ 0.2) at A-site led to the modified reducibility of LaMnO3, as well as the increased molar ratio of Mn4+/Mn3+ and Oads/Ototal, which was benificial for NO oxidation. Moreover, the increase of NO adsorption amount and the shift of the decomposition temperature of nitrates to lower temperautre with the aid of appropriate Pr component accounted for the enhanced activity.