Investigation of nitrous oxide decomposition over highly active and stable bimetallic CoFe-MOR zeolitecatalyst: effective removal and mechanism study

Abstract

In this study, monometallic Co-mordenite (MOR) and bimetallic CoFe-MOR catalysts were prepared via simple wet ion exchange and tested for N₂O decomposition. Strong promotion effect of Fe on the activity and stability of Co ions in the zeolites was observed. To investigate the origin of this promotion effect, X-ray diffraction, H₂-temperature programmed reduction, UV-Vis spectroscopy, extended X-ray absorption fine structure analysis, and N₂O temperature-programmed desorption were used to characterize the bimetallic and monometallic catalysts. The characteristic results indicated that higher contents of Co ions located at β sites after Fe addition provided cooperation on N₂O splitting by two neighboring Co ions. Consequently, a greater amount of surface NO_x species were formed in situ and were more strongly bonded to the catalyst, facilitating the removal of O and increasing the activity. Moreover, extended X-ray absorption fine structure analysis indicated that β-type Co ions exhibited stronger coordination to framework oxygen after Fe addition, and higher exchange level was obtained in the bimetallistic CoFe-MOR. Both of them contribute to prevent the relocation of Co²⁺ ions to form cobalt oxides, thus, high activity was maintained. Consequently, the CoFe-MOR catalyst demonstrates a superior catalytic activity and a high durability in N₂O decomposition, showing great potential as a cost-effective catalyst for N₂O elimination in future applications.