Engineering yolk-shell MnFe@CeO x @TiO x nanocages as a highly efficient catalyst for selective catalytic reduction of NO with NH 3 at low temperatures.

To broaden the reaction temperature range and improve the H 2 O-resistance of manganese-based catalysts, yolk-shell structured MnFe@CeO x @TiO x nanocages were prepared. The CeO 2 shell could effectively increase the oxygen vacancy defect sites, and the TiO 2 shell could remarkably improve the surface acid sites. Combining the advantages of the two shells could effectively solve the above questions. The catalytic efficiency of the yolk-shell MnFe@CeO x @TiO x -40 nanocages could reach above 90% in the range of 120-240 °C, and the water resistance could reach 90% at 240 °C. On the one hand, the construction of double shells could significantly increase the proportion of active species (Mn 4+ , Fe 3+ , Ce 3+ and O ads ) and the interface effect between the shell layers could effectively enhance the interaction between metal oxides. On the other hand, the construction of double shells could achieve an appropriate balance between the redox capacity of the catalyst and surface acidity. Simultaneously, in situ DRIFT spectroscopy indicated that the yolk-shell MnFe@CeO x @TiO x -40 nanocages mainly followed the L-H mechanism during the NH 3 -SCR reaction. Finally, this double-shell structure strategy provided a new idea for constructing a Mn-based catalyst with a wide temperature window and better low-temperature water resistance.