Interface Induced by Hydrothermal Aging Boosts the Low-Temperature Activity of Cu-SSZ-13 for Selective Catalytic Reduction of NO.

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 from diesel engine exhaust. Here, we elaborately design and conduct an in-depth investigation of the synthetic effects of hydrothermal aging and SO poisoning on pristine Cu-SSZ-13 and Cu-SSZ-13@CeZrO core@shell structure catalysts (Cu@CZ). It has been discovered that Cu@CZ susceptible to 750 °C with 5 vol % HO followed by 200 ppm SO with 5 vol % HO (Cu@CZ-A-S) could still maintain nearly 100% NO 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 NO 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 to generate the active NHNO* intermediate, which readily decomposes into N and HO. 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-SCR activity and improves the coresistance of the Cu@CZ catalyst to sulfur poisoning and hydrothermal aging.