Effects of zeolite channel walls and cation migration on N2O decomposition energies in Fe/ZSM-5

Density functional theory was used to compute minimum energy structures for surface intermediates involved in the catalytic decomposition of N2O over Fe/ZSM-5. The calculations were performed using a computational cluster containing only 5 tetrahedral zeolite atoms, and then repeated using a cluster with two full 10-membered zeolite rings. The differences between these two sets of calculations suggest that using a larger computational cluster allows the iron cation to occupy a site of higher coordination. This is accompanied by small changes in the computed values of ΔE for the five mechanistic reaction steps of N2O decomposition. Replicating the final geometry of the smaller cluster within the larger cluster indicated that longer-range interactions with the zeolite channel walls do not significantly affect the energies of the mechanistic steps studied.