Remarkable N₂-selectivity enhancement of NH₃-SCR over HPMo modified MnCo-BTC@SiO₂ catalyst

In this work, the phosphomolybdate (HPMo) modification strategy was applied to improve the N-2 selectivity of MnCo-BTC@SiO2 catalyst for the selective catalytic reduction of NOx, and further, the mechanism of HPMo modification on enhanced catalytic performance was explored. Among MnCo-BTC@SiO2-x catalysts with different HPMo concentrations, MnCo-BTC@SiO2-0.75 catalyst exhibited not only the highest NH3-SCR performance (similar to 95% at 200-300 degrees C) but also the best N-2 selectivity (exceed 80% at 100-300 degrees C) due to the appropriate redox capacity, greater surface acidity. X-ray photoelectron spectrometer (XPS) and temperature programmed reduction of H-2 (H-2-TPR) results showed that the modification with HPMo reduced the oxidation-reduction performance of the catalyst due to electron transfer from Mo5+ to Mn4+/Mn3+ and prevent the excessive oxidation of ammonia adsorption species. NH3 temperature-programmed desorption of (NH3-TPD) results showed that the modification with HPMo could significantly improve the surface acidity and NH3 adsorption, which enhance the catalytic activity and N-2 selectivity. In-situ diffused reflectance infrared Fourier transform spectroscopy (in-situ DRIFTS) revealed that modification with HPMo increased significantly the amount of adsorbed NH3 species on the Bronsted acid site and C-B/C-L, it suppressed the production of N2O by inhibiting the production of NH species, the deep dehydrogenation of ammonia adsorption species. This study provided a simple design strategy for the catalyst to improve the low-temperature catalytic performance and N-2 selectivity. (c) 2023 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.