Density Functional Study on Adsorption of NH and NO on the γ-FeO (111) Surface.

γ-FeO is considered to be a promising catalyst for the selective catalytic reduction (SCR) of nitrogen oxide (NO). In this study, first-principle calculations based on the density function theory (DFT) were utilized to explore the adsorption mechanism of NH, NO, and other molecules on γ-FeO, which is identified as a crucial step in the SCR process to eliminate NO from coal-fired flue gas. The adsorption characteristics of reactants (NH and NO) and products (N and HO) at different active sites of the γ-FeO (111) surface were investigated. The results show that the NH was preferably adsorbed on the octahedral Fe site, with the N atom bonding to the octahedral Fe site. Both octahedral and tetrahedral Fe atoms were likely involved in bonding with the N and O atoms during the NO adsorption. The NO tended to be adsorbed on the tetrahedral Fe site though the combination of the N atom and the Fe site. Meanwhile, the simultaneous bonding of N and O atoms with surface sites made the adsorption more stable than that of single atom bonding. The γ-FeO (111) surface exhibited a low adsorption energy for N and HO, suggesting that they could be adsorbed onto the surface but were readily desorbed, thus facilitating the SCR reaction. This work is conducive to reveal the reaction mechanism of SCR on γ-FeO and contributes to the development of low-temperature iron-based SCR catalysts.