Redox-induced engineering of amorphous/crystalline MnFeO catalyst enables HO/SO-tolerant NO abatement at ultra-low temperatures.

Enhancing resistance to HO and SO poisoning below 150 °C is essential for advancing Mn-based oxide catalysts in ultra-low temperature NH-SCR of NO. To address this challenge, an amorphous/crystalline MnFe catalyst with engineered Mn-O-Fe interfaces and abundant surface defects was developed using a redox-induced precipitation method. The optimized MnFe catalyst demonstrates exceptional catalytic performance, achieving over 90 % NO conversion and N selectivity across a broad 120-260 °C range under highly humid conditions (15 vol% HO). Most significantly, MnFe maintains remarkable stability under high humidity and SO at 120 °C for 60 h, vastly outperforming conventionally coprecipitated MnFe(CP), which gradually deactivates. This superior performance is attributed to the uniform elemental distribution in MnFe, which enhances the Mn-O-Fe redox cycle through improved electron transfer. These features promote superior low-temperature reducibility and acidity, enabling effective reactant adsorption and activation. Mechanistic studies further reveal that SO exposure deactivates MnFe(CP) by forming ammonium (bi)sulfates and MnSO, which hinder reactant adsorption and subsequent reactions. In contrast, the engineered Mn-O-Fe interfaces in MnFe enable Fe species to preferentially interact with SO, shielding Mn from sulfation and significantly reducing deactivation. This work demonstrates a significant breakthrough in catalyst design for ultra-low temperature NH-SCR, paving the way for the broader application of Mn-based catalysts in industrial NO control technologies.