Facile H₂O-Contributed O₂Activation Strategy over Mn-Based SCR Catalysts to Counteract SO₂Poisoning

Abstract

Mn-based catalysts preferred in low-temperature selective catalytic reduction (SCR) are susceptible to SO₂ poisoning. The stubborn sulfates make insufficient O₂ activation and result in deficient reactive oxygen species (ROS) for activating reaction molecules. H₂O has long been regarded as an accomplice to SO₂, hastening catalyst deactivation. However, such a negative impression of the SCR reaction was reversed by our recent research. Here, we reported a H₂O contribution over Mn-based SCR catalysts to counteract SO₂ poisoning through accessible O₂ activation, in which O₂ was synergistically activated with H₂O to generate ROS for less deactivation and more expected regeneration. The resulting ROS benefited from the energetically favorable route supported by water-induced <i>E</i>_a reduction and was actively involved in the NH₃ activation and NO oxidation process. Besides, ROS maintained high stability over the SO₂ + H₂O-deactivated γ-MnO₂ catalyst throughout the mild thermal treatment, achieving complete regeneration of its own NO disposal ability. This strategy was proven to be universally applicable to other Mn-based catalysts.