Resolving NO-CO competitive adsorption in CO-SCR: The role of Ni doping in Mn-Ce catalysts

Traditional Mn-Ce catalysts for selective catalytic reduction (SCR) of NO with CO (CO-SCR) in iron and steel flue gases are often hindered by competitive adsorption of NO and CO, which compromises catalytic efficiency. In this study, we present a Ni-doped Mn-Ce catalyst that overcomes these challenges, achieving 96 % NO conversion, 98 % N 2 selectivity, and 44 % CO conversion at 175 °C. Comprehensive characterization of the catalyst reveals that Ni doping significantly enhances Mn-Ce interactions, boosting oxygen vacancy density and promoting efficient redox cycling between Mn 3 + /Mn 4+ and Ce 3+ /Ce 4+ . Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) confirms preferential NO adsorption at oxygen vacancy sites, minimizing CO-NO competition and stabilizing the Langmuir-Hinshelwood mechanism, where both gases co-adsorb and react at oxygen-rich vacancies. Mechanistic insights suggest that Ni facilitates electron transfer, weakening the N–O bond in NO and accelerating its dissociation, resulting in faster NO reduction. This study establishes Ni doping as a promising strategy for improving the low-temperature performance of Mn-Ce-based CO-SCR catalysts, paving the way for more efficient catalytic systems.