Regulation of binary active sites on MnOx based catalysts for efficient selective catalytic oxidation of NH3

The selective catalytic oxidation of NH 3 (NH 3 -SCO) is a key technology for controlling NH 3 emissions, but conventional MnO x catalysts suffer from low N 2 selectivity and moderate activity. In this work, a series of MMnO x (M = Mo, W, Sm) bimetallic oxide catalysts were fabricated to regulate the acid–redox properties of MnO x through interactions with secondary metal species for highly efficient NH 3 oxidation. The characterization results show that the introduction of M components can significantly enhance the specific surface area and NH 3 adsorption capacity of MnO x , which generates synergistic adsorption and oxidation functions for NH 3 activation, thereby promoting NH 3 -SCO reaction via internal selective catalytic reduction (i-SCR) pathway. Sm significantly enhances the redox properties and surface oxygen vacancies of MnO x , which facilitates the activation of NH 3 . Consequently, SmMnO x achieves 90% NH 3 conversion at 255 °C (60 °C lower than MnO x ) with > 85% N 2 selectivity. In contrast, W addition suppresses the oxidation ability due to the formation of MnWO 4 species, leading to poor low-temperature activity. Mo addition also forms MnMoO 4 , but the increased surface area, enhanced acidity, and separation of active sites allow MoMnO x to outperform MnO x . These findings indicate that constructing M–Mn binary active sites can regulate the balance between surface acidity and oxidation capability, thereby providing a design strategy for high-performance Mn-based NH 3 -SCO catalysts through the rational selection of secondary metal components to establish complementary adsorption–redox functions.