Interface Induced by Hydrothermal Aging Boosts the Low-Temperature Activity of Cu-SSZ-13 for Selective Catalytic Reduction of NOx

Hitherto, sulfur poisoning and hydrothermal aging have still been the challenges faced in practical applications of the Cu-SSZ-13 catalyst for the selective catalytic reduction (SCR) of NO x from diesel engine exhaust. Here, we elaborately design and conduct an in-depth investigation of the synthetic effects of hydrothermal aging and SO 2 poisoning on pristine Cu-SSZ-13 and Cu-SSZ-13@Ce 0.75 Zr 0.25 O 2 core@shell structure catalysts (Cu@CZ). It has been discovered that Cu@CZ susceptible to 750 °C with 5 vol % H 2 O followed by 200 ppm SO 2 with 5 vol % H 2 O (Cu@CZ-A-S) could still maintain nearly 100% NO x conversion across the significantly wider temperature region of 200–425 °C, which is remarkably broader than that of the Cu-SSZ-13-A-S (300–400 °C) counterpart. The experimental results show that the hydrothermal aging process results in the migration of highly active Cu species within the cage of Cu-SSZ-13 to the CZ surface, forming CuO/CZ with abundant interfaces, which significantly enhances the adsorption and subsequent activation of NO, leading to the generation of reactive N 2 O 3 and HONO intermediates. Moreover, density functional theory (DFT) calculations reveal that the H of the HONO* species can function as Brønsted acid sites, effectively adsorbing NH 3 to generate the active NH 4 NO 2 * intermediate, which readily decomposes into N 2 and H 2 O. Furthermore, this pathway is the rate-determining step with an energy barrier of 0.93 eV, notably lower than that of the “standard SCR” pathway (1.42 eV). Therefore, the formation of the new CuO/CZ interface profoundly boosts the low-temperature NH 3 -SCR activity and improves the coresistance of the Cu@CZ catalyst to sulfur poisoning and hydrothermal aging.