Insights into adsorption performances and direct decomposition mechanisms of NO on [FeO]1+-ZSM-5: A density functional theory study

The density functional theory (DFT) has been employed to systematically investigate the successive adsorption performances of two NO molecules onto [FeO](1+)-ZSM-5 surface and subsequent direct decomposition mechanisms by using cluster model in this paper. The adsorption results indicate that there are four stable adsorption configurations of the first NO molecule on [FeO](1+)-ZSM-5, all of which are exothermic and strong chemisorption. Beginning with different adsorption configurations of first NO molecule on [FeO](1+)-ZSM-5 followed by the adsorption of the second NO molecule, all four direct decomposition mechanisms are studied in which N2O molecule acts as the key reaction intermediate, N-2 and O-2 act as the target products. Based on thermodynamic analysis, eta(2)-NO path that starts with adsorption of the first NO as O-down and follows the Eley-Rideal mechanism is proposed, in which ONNO species and N2O are the key catalytic intermediates. The full catalytic reaction is exothermic by 43.76 kcal/mol. The rate-determining step is the formation of N-2(ads), i.e. N2O(ads) -> N-2(ads) + O(ads) and its barrier energy is 39.09 kcal/mol.