Insights into the Roles of Different Iron Species on Zeolites for N₂O Selective Catalytic Reduction by CO

Iron zeolites are promising candidates for mitigating nitrous oxide (N₂O), a potent greenhouse gas and contributor to stratospheric ozone destruction. However, the atomic-level mechanisms by which different iron species, including isolated sites, clusters, and particles, participate in N₂O decomposition in the presence of CO still remain poorly understood, which hinders the application of the reaction in practical technology. Herein, through experiments and density functional theory (DFT) calculations, we identified that isolated iron sites were active for N₂O activation to generate adsorbed O* species, which readily reacted with CO following the Eley-Rideal (E-R) mechanism. In contrast, Fe₂O₃ particles exhibited a different reaction pathway, directly reacting with CO to generate oxygen vacancies (O_v), which could efficiently dissociate N₂O following the Mars-van Krevelen (MvK) mechanism. Moreover, the transformation of iron oxide clusters into undercoordinated FeO_<i>x</i> species by CO was also revealed through various techniques, such as CO-temperature-programmed reduction (TPR), and <i>ab initio</i> molecular dynamics (AIMD) simulations. Our study provides deeper insights into the roles of different iron species in N₂O-SCR by CO, and is anticipated to facilitate the understanding of multicomponent catalysis and the design of efficient iron-containing catalysts for practical applications.