MnFe@CeO_x Core–Shell Nanocages for the Selective Catalytic Reduction of NO with NH₃ at Low Temperature

To enable the catalytic performance and water (H2O) resistance of manganese-based catalysts to be further improved, a series of MnFe@CeOx core–shell nanocages were synthesized. By adjustment of the thickness of the CeO2 shell layer, it was found that the MnFe@CeOx-60 catalyst with a shell layer thickness of 60 nm could exhibit more than 80% NO removal efficiency at 120–250 °C. In addition, it could exhibit better H2O resistance at 160 °C. A series of characterizations proved that the MnFe@CeOx-60 catalyst had abundant oxygen vacancy defect sites and surface acid sites. In addition, the MnFe@CeOx-60 catalyst had more Mn4+, Fe3+, Ce3+, and surface-adsorbed oxygen (Oads) species, as well as strong interactions between MnOx, FeOx, and CeOx, so that the catalyst had better catalytic activity. This indicated that the unique interface diffusion effect produced by construction of the CeO2 shell could remarkably enhance the catalytic performance and H2O resistance. Simultaneously, the in situ diffuse-reflectance infrared Fourier transform analysis showed that the MnFe@CeOx-60 catalyst mainly followed the L–H reaction mechanism during the NH3 selective catalytic reduction (SCR) reaction. Finally, building a shell layer could skillfully utilize the diffusion between different species to realize strong interaction among active species, which was of great significance and universality.