Temperature-programmed reduction (H2-TPR) was employed to quantitatively characterize the active oxygen species generated from a high Fe-loading Fe/ZSM-5 catalyst exposed to N2O at 250 ℃. Fe-O-Fe2+ dimer was determined as the active iron complex for N2O decomposition to produce the active oxygen. Reduction of Fe3+ to Fe2+ by H2 in the dimer and removal of OH- groups from Fe2+ dimer by heating Fe/ZSM-5 to 700 ℃ were the prerequisites for the formation of this active Fe complex. A linear correlation with a slope of 1.0 between the amount of Fe-O-Fe2+ and that of active oxygen species was observed. Maximum amount of active oxygen species can be generated by reducing Fe/ZSM-5 catalyst with H2 at the temperatures over 500 ℃ and then heating the resulting product in Ar to 700 ℃, followed by N2O exposure at 250 ℃.tThe ratio of the total number of oxygen atoms (Ode) deposited by interaction of Fe-O-Fe2+ with N2O to the amount of Fe-O-Fe2+ was 2. However, not all the deposited oxygen atoms were active oxygen (Oa); the ratio of Oa and Ode was 0.5. The iron dimer complex composing active oxygen is a five-atom ion Fe2O32+; the most probable structure is as follows: Temperature-programmed reduction (H2-TPR) was employed to quantitatively characterize the active oxygen species generated from a high Fe-loading Fe / ZSM-5 catalyst exposed to N2O at 250 ° C. Fe-O-Fe2 + dimer was determined as the active iron complex for N2O decomposition to produce the active oxygen. Reduction of Fe3 + to Fe2 + by H2 in the dimer and removal of OH- groups from Fe2 + dimer by heating Fe / ZSM-5 to 700 ° C were the prerequisites for the formation of this active Fe complex . A linear correlation with a slope of 1.0 between the amount of Fe-O-Fe2 + and that of active oxygen species was observed. Maximum amount of active oxygen species can be generated by reducing Fe / ZSM-5 catalyst with H2 at the temperatures over 500 ℃ and then heating the resulting product in Ar to 700 ℃, followed by N2O exposure at 250 ℃. TThe ratio of the total number of oxygen atoms (Ode) deposited by interaction of Fe-O-Fe2 + with N2O to the amount of Fe-O-Fe2 + was 2. However, not all the deposited oxygen the ratio of Oa and Ode was 0.5. The iron dimer complex composing active oxygen is a five-atom ion Fe2O32 +; the most probable structure is as follows: