Promoting mechanism of Mn doping on the NH₃-SCR reaction over the Fe/ -Al₂O₃ catalyst surface

To verify the superiority of Mn-Fe dual-component doped catalysts in terms of deNO(x) performance, the differences of mechanisms in selective catalytic reduction with ammonia (NH3-SCR) between Fe/gamma-Al2O3 and Mn-Fe/gamma-Al2O3 catalysts were investigated by using the density functional theory (DFT). On the surface of the Fe/gamma-Al2O3 catalyst, the NH2 group generated by NH3 dehydrogenation can react with NO and NO2 to form NH2NO and NH2NO2, respectively. The decomposition process of NH2NO is established as the rate-determining step in the reaction between NH3 and NO, while the rate-determining step in the reaction between NH3 and NO2 is the decomposition of NHNO2. Mn doping significantly enhances the catalyst's adsorption performance for O-2 and oxidation ability toward NO, thereby promoting the production of NO2. Additionally, Mn doping markedly reduces the reaction barriers, facilitating the dissociation of NH2NO and NHNO2 on the Mn-Fe/gamma-Al2O3 catalysts. These findings may elucidate the reasons of the effective enhancement of deNO(x) performance in the Mn-doped Fe/gamma-Al2O3 catalysts, which establishes a foundation for the subsequent development and application of Mn-Fe bimetallic-doped SCR deNO(x) catalysts.