Remarkable N-selectivity enhancement of NH-SCR over HPMo modified MnCo-BTC@SiO catalyst.

In this work, the phosphomolybdate (HPMo) modification strategy was applied to improve the N selectivity of MnCo-BTC@SiO catalyst for the selective catalytic reduction of NO, and further, the mechanism of HPMo modification on enhanced catalytic performance was explored. Among MnCo-BTC@SiO-x catalysts with different HPMo concentrations, MnCo-BTC@SiO-0.75 catalyst exhibited not only the highest NH-SCR performance (∼95% at 200-300°C) but also the best N selectivity (exceed 80% at 100-300°C) due to the appropriate redox capacity, greater surface acidity. X-ray photoelectron spectrometer (XPS) and temperature programmed reduction of H (H-TPR) results showed that the modification with HPMo reduced the oxidation-reduction performance of the catalyst due to electron transfer from Mo to Mn/Mn and prevent the excessive oxidation of ammonia adsorption species. NH temperature-programmed desorption of (NH-TPD) results showed that the modification with HPMo could significantly improve the surface acidity and NH adsorption, which enhance the catalytic activity and N selectivity. In-situ diffused reflectance infrared Fourier transform spectroscopy (in-situ DRIFTS) revealed that modification with HPMo increased significantly the amount of adsorbed NH species on the Bronsted acid site and C/C, it suppressed the production of NO 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 selectivity.