Role of aggregated Fe oxo species in N2O decomposition over Fe/ZSM-5

The effects of aggregated Fe oxo (FeO x ) species on N 2 O decomposition activity of aqueous ion-exchanged Fe/ZSM-5 were investigated. Aggregation of FeO x species was achieved by thermal treatment of the Fe/ZSM-5 catalysts at different temperatures (600–900 °C) in pure Ar. The characterizations were carried out using X-ray diffraction, N 2 physisorption, UV-Vis diffuse reflectance spectroscopy, X-ray absorption fine structure spectroscopy, pulse-response analysis, and O 2 -temperature-programmed desorption. The FeO x species on the external framework of the ZMS-5 zeolite played a dominant role in N 2 O decomposition over Fe/ZSM-5. By studying the relationship between the contents of the various existing iron species and activity of the different catalysts, polynuclear FeO x appeared to be the main active phase for N 2 O decomposition. Additionally, Fe–O with a long bond length ((Fe–O) 2 ) in amorphous polynuclear FeO x was positively correlated to the activity of the catalysts, indicating that (Fe–O) 2 was the active species for N 2 O decomposition. Fe–O species, with a long bond length, in polynuclear amorphous Fe oxo species are the real active species of Fe/ZSM-5 towards N 2 O decomposition. Apparent pre-exponential factor is important to the reaction rate.