Low-Coordination Mn Single Atoms on CeO ₂ Nano-Islands for Boosting Ultra-Low Temperature NH ₃ –SCR Activity and SO ₂ Resistance

Mn-based catalysts are among the most promising candidates for the ultralow-temperature (≤150 °C) selective catalytic reduction of NOx with NH3 (NH3–SCR). However, their narrow operating temperature window and insufficient resistance to SO2/H2O limit their broader practical application. In this work, Mn single atoms featuring a unique low-coordination configuration are uniformly anchored onto CeO2 nanoislands that were predeposited on H2Ti3O7 nanotubes (TNTs) via a newly developed in situ redox self-assembly strategy. The resulting catalyst, denoted as LC-Mn/CeO2, exhibits exceptional ultralow-temperature NH3–SCR activity and SO2 resistance. It achieves over 90% NOx conversion at 100 °C and maintains nearly 90% conversion for over 20 h at 140 °C in the presence of 50 ppm of SO2 and 10 vol % H2O. Experimental and DFT results reveal that the unique electronic modulation of the low-coordination Mn centers facilitates the formation of asymmetric oxygen vacancies. By promoting the oxidation of NO to NO2, these vacancies significantly enhance the low-temperature reaction rate of the NH3–SCR reaction. Simultaneously, the electron-rich environment of Mn sites suppresses the oxidation of SO2 by weakening the Mn–SO2 charge transfer, thereby improving SO2 resistance. Our work provides a novel strategy of modulating the coordination environment of single atoms to enhance ultralow-temperature activity and SO2/H2O resistance.