Study on CO-SCR denitrification performance of Ho-modified OMS-2 catalyst

One-step hydrothermal synthesis method was used to prepare the Ho-doped OMS-2 catalyst (Hox-OMS-2) and the reactivity for selective catalytic reduction of NO with CO (CO-SCR) was examined. The outcomes demonstrated that the Ho0.05-OMS-2 catalyst displayed very attractive CO-SCR activity at 225 °C when the Ho/Mn molar ratio was 0.05, e.g., approximately 100% NO conversion and N2 selectivity. Furthermore, even in the presence of 0.02% SO2, the Ho0.05-OMS-2 catalyst can retain more than 80% NO conversion at 200–250 °C, and the catalyst has good sulfur resistance. SEM, XRD, BET, XPS, H2-TPR, and NH3-TPD were used to characterize the catalysts and analyze how the presence of Ho species in Hox-OMS-2 affected their physicochemical properties and reactivity. The outcomes show that the lattice expansion, decreased crystallinity, high specific surface area, increased Mn4+ concentration, enhanced surface oxygen vacancies and more Brønsted acidic bits can all contribute to the improved low-temperature activity of Hox-OMS-2 catalysts. Based on the In situ DRIFTS analysis, possible E-R mechanism (30–100 °C) and L-H mechanism (125–300 °C) of the catalysts were proposed.