Investigation of nitrous oxide decomposition over highly active and stable bimetallic CoFe-MOR zeolite catalyst: 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 NOx 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.