Interface\nInduced by Hydrothermal Aging Boosts the\nLow-Temperature Activity of Cu-SSZ-13 for Selective Catalytic Reduction\nof NO<sub><i>x</i></sub>

Hitherto,\nsulfur poisoning and hydrothermal aging have still been\nthe challenges faced in practical applications of the Cu-SSZ-13 catalyst\nfor the selective catalytic reduction (SCR) of NO<sub><i>x</i></sub> from diesel engine exhaust. Here, we elaborately design and\nconduct an in-depth investigation of the synthetic effects of hydrothermal\naging and SO<sub>2</sub> poisoning on pristine Cu-SSZ-13 and Cu-SSZ-13@Ce<sub>0.75</sub>Zr<sub>0.25</sub>O<sub>2</sub> core@shell structure catalysts\n(Cu@CZ). It has been discovered that Cu@CZ susceptible to 750 °C\nwith 5 vol % H<sub>2</sub>O followed by 200 ppm SO<sub>2</sub> with\n5 vol % H<sub>2</sub>O (Cu@CZ-A-S) could still maintain nearly 100%\nNO<sub><i>x</i></sub> conversion across the significantly\nwider temperature region of 200–425 °C, which is remarkably\nbroader than that of the Cu-SSZ-13-A-S (300–400 °C) counterpart.\nThe experimental results show that the hydrothermal aging process\nresults in the migration of highly active Cu species within the cage\nof Cu-SSZ-13 to the CZ surface, forming CuO/CZ with abundant interfaces,\nwhich significantly enhances the adsorption and subsequent activation\nof NO, leading to the generation of reactive N<sub>2</sub>O<sub>3</sub> and HONO intermediates. Moreover, density functional theory (DFT)\ncalculations reveal that the H of the HONO* species can function as\nBrønsted acid sites, effectively adsorbing NH<sub>3</sub> to\ngenerate the active NH<sub>4</sub>NO<sub>2</sub>* intermediate, which\nreadily decomposes into N<sub>2</sub> and H<sub>2</sub>O. Furthermore,\nthis pathway is the rate-determining step with an energy barrier of\n0.93 eV, notably lower than that of the “standard SCR”\npathway (1.42 eV). Therefore, the formation of the new CuO/CZ interface\nprofoundly boosts the low-temperature NH<sub>3</sub>-SCR activity\nand improves the coresistance of the Cu@CZ catalyst to sulfur poisoning\nand hydrothermal aging.