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. It was investigated that the doping of lattice Fe contributes to a slight reduction in the catalyst's reducibility and a moderate increase the amounts of Lewis acid sites. Fe₂O₃, which produced through calcination, plays a crucial role in enhancing surface-adsorbed oxygen and Bronsted acid sites. These synergistic effects regulate both the acidic and redox properties of the catalyst, facilitating NH₃ adsorption and activation while controlling NH₃ overoxidation, thus broadening the operational temperature range and improving N₂ selectivity. Furthermore, in situ diffuse reflectance infrared spectroscopy (DRIFTS) characterization demonstrated that the NH₃-SCR reaction on the catalyst primarily follows an Eley-Rideal (E-R) 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.