Mn-based catalysts have attracted much attention in the
field of
the low-temperature NH3 selective catalytic reduction (NH3–SCR) of NO. However, their poor SO2 resistance,
low N2 selectivity, and narrow operation window limit the
industrial application of Mn-based oxide catalysts. In this work,
NiMnFeOx catalysts were prepared by the
layered double hydroxide (LDH)-derived oxide method, and the optimized
Ni0.5Mn0.5Fe0.5Ox catalyst had the best denitration activity, excellent N2 selectivity, a wider active temperature range (100–250
°C), higher thermal stability, and better H2O and/or
SO2 resistance. A transient reaction revealed that Ni0.5Mn0.5Fe0.5Ox inhibited the NH3 + O2 + NOx pathway to generate N2O, which may be
the main reason for its improved N2 selectivity. Combining
experimental measurements and density functional theory (DFT) calculations,
we elucidated at the atomic level that sulfated NiMnFeOx (111) induces the adjustment of the acidity/basicity
of up and down spins and the ligand field reconfiguration of the Mn
sites, which improves the overall reactivity of NiMnFeOx catalysts. This work provides atomic-level insights
into the promotion of NH3–SCR activity by NiMnFeOx composite oxides, which are important for
the practical design of future low-temperature SCR technologies.