Design of a hierarchical Fe-ZSM-5@CeO2 catalyst and the enhanced performances for the selective catalytic reduction of NO with NH3

Selective catalytic reduction of NOx by NH3 (NH3-SCR) is an effective technique for the abatement of NOx. Development of SCR catalyst is the core of the technique. Herein, a hierarchical Fe-ZSM-5@CeO2 catalyst with CeO2 nanoparticles decorating is originally fabricated via dopamine polymerization for NH3-SCR. Fe-ZSM5@CeO2 possess a NOx conversion over 90% and N-2 selectivity over 98% in the temperature range of 250-400 degrees C, showing an advanced catalytic activity compared with Fe-ZSM-5/CeO2. The synergistic effect of FeZSM-5 and CeO2 over Fe-ZSM-5@CeO2 facilitates the formation of redox cycle between Ce3+/Ce4+ redox-couple and high rate active oxygen species (O-beta and O-gamma), leading to the enhanced NH3-SCR performance. The feature of hierarchical structure with CeO2 outside provides a pathway to convert NO to NO2, facilitating the fast SCR. Meanwhile, the formed NO2 can activate Fe2+/Fe3+ redox-couple, offering an extra redox cycle which can further contribute to fast SCR. The outer CeO2 layer can also improve the water resistance of Fe-ZSM-5 as the catalytic activity of Fe-ZSM-5@CeO2 was impervious when exposed to 10% H2O. To be concluded, the hierarchical Fe-ZSM-5@CeO2 is proved to be a promising candidate for NH3-SCR due to its uniform distribution of active sites and the synergistic effect of Fe-ZSM-5 and CeO2 species.