Improved N2 selectivity for low-temperature NOx reduction over etched ZSM-5 supported MnCe oxide catalysts

Developing a high-efficiency catalyst with both superior low-temperature activity and good N₂ selectivity is still challenging for the NH₃ selective catalytic reduction (SCR) of NO_x from mobile sources. Herein, we demonstrate the improved low-temperature activity and N₂ selectivity by regulating the redox and acidic properties of MnCe oxides supported on etched ZSM-5 supports. The etched ZSM-5 enables the highly dispersed state of MnCeO_x species and strong interaction between Mn and Ce species, which promotes the reduction of CeO₂, facilitates electron transfer from Mn to Ce, and generates more Mn⁴⁺ and Ce³⁺ species. The strong redox capacity contributes to forming the reactive nitrate species and -NH₂ species from oxidative dehydrogenation of NH₃. Moreover, the adsorbed NH₃ and -NH₂ species are the reactive intermediates that promote the formation of N₂. This work demonstrates an effective strategy to enhance the low-temperature activity and N₂ selectivity of SCR catalysts, contributing to the NO_x control for the low-temperature exhaust gas during the cold-start of diesel vehicles.