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

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 similar to 100%, N-2 selectivity above 90% at a temperature similar to 140 degrees C. The characterization results, such as BET, XRD, H-2-TPR, O-2/NH3-TPD and XPS, indicated that this nano-cup structure catalyst possesses high concentration and dispersion of Mn4+ active species, strong chemisorbed O- or O-2(2-) species and highly stable MnOX active components over the annular structures of the TiO2 shell and SiO2 sphere, and thus enhanced the low-temperature SCR performance.