Three-dimensional ordered macroporous cerium–manganese composite oxide for NO oxidation

Abstract

NO_x is one of the main sources of air pollution, which primarily comes from automobile exhausts. Rare earth-based catalysts for NO oxidation have excellent oxygen storage and release performance and good structural stability. Herein, a series of three-dimensional ordered microporous (3DOM) cerium–manganese composite oxide catalysts with different cerium–manganese ratios for NO oxidation were prepared by the sol–gel method. The 3DOM structure improves the contact efficiency of the NO, soot and the catalyst. By incorporating Mn³⁺ ions into the cerium oxide lattice, a Ce–Mn solid solution forms with an ordered macroporous structure, and the interaction between cerium and manganese significantly increases the amount of reactive oxygen species. The catalyst with the optimal cerium–manganese ratio (1 : 2) was able to achieve a conversion rate of 62% at 250 °C, and the highest conversion rate reached 98%, which is far higher than pure cerium oxide and pure manganese oxide catalysts. This work provides a promising catalyst for NO oxidation and soot combustion applications.