Revealing the effects of introducing Fe on the N2 selectivity of Pt-SSZ-13 catalyst for ammonia selective catalytic oxidation

Abstract

Ammonia slip in diesel engines can pose serious threats to the ecosystem and human health. Pt-SSZ-13 is an efficient NH₃-SCO catalyst but suffers from poor N₂ selectivity at high temperatures. In this work, introducing Fe as an additional active component into the Pt-SSZ-13 catalyst maintained its low-temperature NH₃ oxidation activity and significantly improved its N₂ selectivity by efficiently converting the by-products. EPR and XPS results indicate that there are interactions between Pt and Fe in the catalyst, with Fe transferring electrons to Pt, resulting in an increased content of Pt⁰ and Fe³⁺. The increased amount of Pt⁰ is beneficial for the low-temperature NH₃-SCO activity. Fe³⁺ species are beneficial for the N₂O-SCR reaction at the Fe–OH site at medium temperatures to remove the by-product N₂O. For the NO species, the Fe³⁺ species contribute to the occurrence of the i-SCR reaction at high temperatures. This work provides a new direction for optimizing the N₂ selectivity of Pt-based NH₃-SCO catalysts for diesel vehicle exhaust purification.