Density functional theory study on the reaction mechanism of selective catalytic reduction of NO by NH3 over the γ-Fe2O3 (001) surface

The de-NOx reaction mechanism of NH3, NO, and O-2 molecules over the gamma-Fe2O3 (0 0 1) surface was studied by a density functional theory calculation. For the gas adsorption property, NH3 and NO can be adsorbed on Fe-top sites. O-2 is adsorbed on Hollow site to form adsorbed oxygen. The de-NOx reactions mainly follow Eley-Rideal mechanism and three reaction schemes such as (1) NH3 and NO, (2) NO and O-2, and (3) NH3, NO, and O-2 were proposed. Scheme 1 has five steps: (1) NH3 adsorption, (2) NH3 dehydrogenation, (3) NH2NO formation, (4) NHNO formation, (5) N-2 and H2O formation. Scheme 2 is the oxidation path of NO, containing NO2 and NO3 formation. It confirms that adsorbed oxygen structure can promote the adsorption and oxidation of NO. Scheme 3 has five steps: (1) NH3 dehydrogenation, (2) NH2NO2 formation, (3) NHNO2 formation, (4) N2O formation, and (5) N-2 formation.