Insight into the synergism between MnO2 and acid sites over Mn–SiO2@TiO2 nano-cups for low-temperature selective catalytic reduction of NO with NH3

Abstract

The rational synthesis of low-temperature catalysts with high catalytic activity and stability is highly desirable for the selective catalytic reduction of NO with NH₃. Here we synthesized a Mn–SiO₂/TiO₂ nano-cup catalyst via the coating of the mesoporous TiO₂ layers on SiO₂ spheres and subsequent inlay of MnO₂ nanoparticles in the narrow annulus. This catalyst exhibited superior catalytic SCR activities and stability for low-temperature selective catalytic reduction of NO with NH₃, with NO conversion of ∼100%, N₂ selectivity above 90% at a temperature ∼140 °C. The characterization results, such as BET, XRD, H₂-TPR, O₂/NH₃-TPD and XPS, indicated that this nano-cup structure catalyst possesses high concentration and dispersion of Mn⁴⁺ active species, strong chemisorbed O⁻ or O₂²⁻ species and highly stable MnO_X active components over the annular structures of the TiO₂ shell and SiO₂ sphere, and thus enhanced the low-temperature SCR performance.