Synergistic Effect of Iron Doping and Oxide Hybridization Enables Enhanced Low-Temperature NH3-SCR Performance of Manganese Oxide Catalyst
Manganese oxides (MnO x ) catalysts are promising for low-temperature ammonia-selective catalytic reduction (NH₃-SCR), however, the limited N₂ selectivity and the narrow operational temperature range remain challenges. To address these issues, we developed a method involving impregnation doping and high-temperature calcination to hybridize Mn₂O₃ with iron lattice and oxide. This hybrid catalyst maintains a NO x conversion rate above 90% within the broad temperature window of 175–300 °C, while achieving N₂ selectivity above 99%. The as prepared Fe-Mn (0.15) exhibits spherical morphology with Fe and Mn uniformly distributed. Through XPS, XAFS, H₂-TPR, NH₃-TPD and catalytic activity tests, we verified that lattice iron doping slightly reduces the reducibility of the catalyst and enhances low-temperature activity (100–200 °C) by increasing Lewis acid sites. Meanwhile, the Fe₂O₃ domains promote high-temperature performance (200–300 °C) by enriching surface oxygen species and Bronsted acid sites. These synergistic effect regulates both the acidic and redox properties of the catalyst, facilitating NH 3 activation while suppressing over-oxidation, leading to superior NH 3 -SCR performance. Furthermore, in situ DRIFTS measurements confirmed that the reaction proceeds predominantly via a Langmuir-Hinshelwood (L-H) mechanism. This work reveals the synergistic effects of Fe lattice doping and Fe₂O₃ composite on MnO x , offering new insights for developing advanced low-temperature catalysts. Graphical
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