Catalytic oxidation of NO over SmMn2O5 nanostructures derived from different Mn precursors

In this work, SmMn2O5 nanostructures with different morphologies (particles, flower-like, mixed-structure) were effectively synthesized through a hydrothermal method. The differences of the counter anions (CH3COO−, NO3−, and Cl−) in Mn precursors make the periphery of crystal nucleus have different concentrations of ions during the formation of SmMn2O5 nanostructures, which have been used to explain the evolution of morphology. Compared with Pt/Al2O3, the catalytic performance of NO oxidation for three morphologies shows higher maximum efficiency. The 50% conversion temperature is lower (230 °C vs. 275 °C) and the maximum conversion efficiency is higher (81% at 282 °C vs. 68% at 314 °C) for SmMn2O5 with flower-like by comparison with SmMn2O5 with particles and mixture shapes. The specific surface area is in the order of flower-like > mixed-structures > particles, which is the same as the order of performance for NO oxidation of SmMn2O5 nanostructures. The results of XPS and H2-TPR indicate that the superior catalytic performance of SmMn2O5 with flower-like arises from the existence of more amount of Mn4+/ Mn3+, which can act as the surface active sites. This work offers a promising way for the morphological control of SmMn2O5 with Mn precursors to improve the catalytic performance of NO oxidation.