Enhanced low-temperature NH₃-SCR activity and SO₂ tolerance by Cu-SSZ-13/R(Sm, Pr, Y or La)MnO_x coupled catalysts

A series of Cu-SSZ-13/R(Sm, Pr, Y or La)MnO_x composite catalysts were successfully synthesized by the self-assembly method. Among them, the low-temperature NH₃-SCR activity and sulfur resistance of Cu-SSZ-13 are most effectively improved by coupling with SmMnO_x. The abundant adsorbed O_ads species in SmMn₂O₅ can promote the oxidation of NO to NO₂ and trigger the "fast SCR" reaction, which is an important reason for the excellent low-temperature NH₃-SCR activity of the composite catalyst. Moreover, the electron transfer between the SmMn₂O₅ and Cu-SSZ-13 interface facilitates the redox cycling of Mn³⁺/Mn⁴⁺ and Cu²⁺/Cu⁺, thus improving NO conversion and retaining a wide temperature window for the NH₃-SCR reaction. Meanwhile, the SmMnO_x species can be used as sacrificial sulfur-trapping sites, which effectively prevent the sulfation of the copper active sites and thus significantly improve the SO₂ tolerance of the composite catalysts. This work elucidates the synergistic reaction mechanism of Cu-SSZ-13/SmMnO_x coupled catalysts and thereby provides theoretical guidance for the rational design and development of high-efficiency NH₃-SCR catalysts.