Structural Modulation and Adsorptive Behavior of CuFe-LDHs-derived Catalysts through Mn Doping: Dual Enhancement of Low-Temperature Catalytic Performance and Sulfur Resistance

Abstract

Addressing the activity and resistance to toxicity of sintered flue gas at low temperatures is crucial. This study focuses on the design of Mn-doped Cu₃Fe₁-LDHs as a bifunctional catalyst for synergistic CO oxidation in NH₃–SCR. Compared with the Cu₃Fe₁O_x catalysts, the Mn-doped Cu₃Mn_0.25Fe_0.75O_x catalysts achieved dual enhancement of NO_x and CO conversion at low temperature and oxygen-enriched conditions, albeit with lower N₂ selectivity. They also demonstrated good sulfur-resistant performance. Confirming by theoretical calculations and characterization techniques, the chemical bonding configuration of Cu₃Fe₁O_x was verified. Mn is uniformly distributed in the catalyst and formed a solid solution with Cu²⁺ and Fe³⁺ in the crystal lattice. This contributed to the stable growth of the crystals during synthesis, thus improving the size and morphology of the crystals and providing more active sites. Mn introduction also promoted charge transfer between Cu²⁺ and Fe³⁺, and enhanced the catalyst’s adsorption capacity and reactivity. Chemisorption analysis revealed that the incorporation of Mn significantly improved the catalyst’s reduction capacity, oxygen adsorption ability, and acidic sites. Furthermore, in situ DRIFTS and DFT calculations demonstrated that Mn doping improved NH₃ and CO adsorption, thereby improving the catalyst’s overall performance. The SO₂ adsorption results showed that Mn doping enhanced the surface acidity of the catalyst, reducing SO₂ adsorption and sulfate formation. The development of this catalyst has important industrial application value for ultralow emission of sintering flue gas.