Enhanced low-temperature NO oxidation by iron-modified MnO2 catalysts

Series of Fe-modified MnO2 catalysts were prepared to improve low-temperature NO oxidation. Introduction of Fe3+ resulted in a phase transformation from α-MnO2 to ε-MnO2. Hexagonal Fe0.32MnO2 exhibited the highest activity with the lowest T50 of 156 °C and the maximum NO conversion of 80% at 250 °C. It also possessed the best reducibility and abundant readily available oxygen species, which facilitated the oxidation of NO. Major differences in the NO oxidation reaction route between α-MnO2 and Fe0.32MnO2 were the adsorption sites and the type of intermediates. The synergetic effect between Fe and Mn enhanced the activation of NO and O2.