Promotion of the selective catalytic reduction of NOx with NH3 over microporous Cu-SSZ-13 by H2O and OH groups at low temperatures: a density functional theory study

Abstract

The successful commercialization of microporous Cu-SSZ-13 catalysts in the selective catalytic reduction (SCR) of NO_x with NH₃ has attracted extensive attention and debate on the mechanism of their excellent activity and water resistance. Herein, the complete standard NH₃-SCR reaction pathways over Cu-SSZ-13 were investigated via density functional theory (DFT) calculations, and a water/OH group-mediated NH₃-SCR mechanism over Cu-SSZ-13 was reported. We found that the activation of NO at the Cu sites and the participation of water significantly reduce the energy barrier for the regeneration of Cu^IIOH(NH₃)₃⁺ active sites. Moreover, the coupling effect of Brønsted acid and Cu–OH sites not only shortens the reaction pathway but also further reduces the energy barrier for the decomposition of the key intermediate NH₂NO. These findings advance the atomic level understanding of the NH₃-SCR reaction and provide insight into the excellent low-temperature NH₃-SCR activity and water resistance of microporous Cu-SSZ-13 catalysts.