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Manganese-based catalysts have a good low-temperature deNOx activity, but the presence of SO2 can cause their poisoning and deactivation, limiting their industrial use. They have been discovered to be more sulfur resistant when iron (Fe) is added. However, the mechanism of Fe as a doping additive to enhance manganese-based catalysts' sulfur resistance is not clear. During this study, the impact of Fe doping for gas adsorption and anti-sulfur poisoning on the β-MnO2 (110) was investigated by using the DFT-D3 calibration. The results indicate that Fe doping promotes the adsorption of NH3 on the Mn sites over the β-MnO2 (110) surface, weakens SO2 adsorption capacity, and the oxidation of SO2 is limited. In addition, Fe doping promotes the decomposition of ammonium sulfate on the catalyst surface and alleviates its blockage of catalytic sites on the catalyst surface. This study can complement the understanding of the anti-sulfur mechanism of Mn-based catalysts and has great significance for the guidance of the design of Mn-based catalysts with good anti-sulfur poisoning. [ABSTRACT FROM AUTHOR]

Selective catalytic reduction of NOx with NH3 is one of the most effective ways to reduce NOx emissions. Manganese-based deNOx catalysts have attracted much attention owing to their unstable valence states. Nickel-foam-supported manganese-based catalysts show excellent low-temperature deNOx activities. However, the detailed deNOx mechanism is still unclear. In this paper, the adsorption mechanism of NH3, NO, and O2 molecules over nickel-foam-supported manganese-based catalysts was studied by a density functional theory. The model of MnO2, Mn2O3, and Mn3O4 clusters loading on the Ni (111) surface was chosen. The results show that MnO2, Mn2O3, and Mn3O4 clusters can be stably adsorbed on the Ni (111) surface accompanied by charge redistributions, which provide a large number of stable adsorption sites for gas molecules. NH3 molecule can be adsorbed on the Ni-top and Mn sites as the coordinated NH3. For MnO2, Mn2O3, and Mn3O4 clusters, Mn3O4 clusters are the most favorable for NH3 adsorption, indicating that they can promote NH3-SCR reaction. NO exists in three adsorption states on the MnxOy/Ni (111) surface and forms different nitrite or nitrate species. Interestingly, NO molecule tends to adsorb on the hollow site of Ni (111) surface. O2 molecule has various adsorption states on the MnxOy/Ni (111) surface. NO molecule is more likely to be adsorbed on the Mn site of the O2–MnxOy/Ni (111) surface to form nitrosyl structure, and some of NO molecules can react with adsorbed oxygen to form the adsorbed NO2 spices, which can facilitate the SCR deNOx reaction. The catalytic activity of Mn3O4/Ni (111) surface is higher than those of MnO2/Ni (111) and Mn2O3/Ni (111) surfaces by comparing the work functions and adsorption properties of NH3, NO, and O2 molecules. [ABSTRACT FROM AUTHOR]