Modulation of Electron-Donation Ability to Enhance the Low-Temperature NO Oxidation Performance of Mn₃O₄/YMn₂O₅

Managing the substantial NO emissions during the cold start of diesel vehicles presents a critical environmental challenge. Enhancing the conversion of NO to NO₂ at low temperatures can significantly improve the efficiency of diesel aftertreatment systems. Manganese-based mullite catalysts are cost-effective and promising for NO oxidation; however, their low-temperature activity requires further enhancement. In this study, we innovatively leverage the strong electronic interactions between Mn₃O₄ and YMn₂O₅ to enhance the low-temperature NO oxidation activity (50% at 200 °C) of Mn₃O₄/YMn₂O₅, demonstrating high activity (CO conversion: T₁₀₀ = 222 °C, C₃H₆ conversion: T₁₀₀ = 209 °C, C₃H₈ conversion: T₁₀₀ = 341 °C, NO maximum conversion: 78.7% at 300 °C) and stability (CO and C₃H₆ conversion: 100%, C₃H₈ conversion: 94.06%, NO conversion: 78.7% at 300 °C for 10 h) under a simulated exhaust gas mixture. Structural analysis (X-ray diffraction (XRD), Raman, and transmission electron microscopy (TEM)) confirmed the uniform coexistence of Mn₃O₄ and YMn₂O₅ phases. Furthermore, X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS) indicated that Mn₃O₄ decreased the average Mn valence state, increased Mn-Mn interactions, and modified Mn-O coordination, contributing to improved catalytic performance. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and density functional theory (DFT) calculations further revealed that Mn₃O₄/YMn₂O₅ enhances electron transfer to adsorbed O₂, reducing its dissociation energy barrier and destabilizing nitrite intermediates, thereby accelerating the Eley-Rideal (E-R) mechanism for NO oxidation.