Modulating the Activity and SO 2 Resistance of α-Fe 2 O 3 Catalysts for NH 3 -SCR of NO x via Crystal Facet Engineering.

The development of Fe-based catalysts for the selective catalytic reduction of NO x by NH3 (NH3 -SCR of NO x ) has garnered significant attention due to their exceptional SO2 resistance. However, the influence of different sulfur-containing species (e.g., ferric sulfates and ammonium sulfates) on the NH3 -SCR activity of Fe-based catalysts as well as its dependence on exposed crystal facets of Fe2 O3 has not been revealed. This work disclosed that nanorod-like α-Fe2 O3 (Fe2 O3 -NR) predominantly exposing (110) facet performed better than nanosheet-like α-Fe2 O3 (Fe2 O3 -NS) predominantly exposing (001) facet in NH3 -SCR reaction, due to the advantages of Fe2 O3 -NR in redox properties and surface acidity. Furthermore, the results of the SO2 /H2 O resistance test at a critical temperature of 250 °C, catalytic performance evaluations on Fe2 O3 -NR and Fe2 O3 -NS sulfated by SO2 + O2 or deposited with NH4 HSO4 (ABS), and systematic characterization revealed that the reactivity of ammonium sulfates on Fe2 O3 catalysts to NO(+O2 ) contributed to their improved catalytic performance, while ferric sulfates showed enhancing and inhibiting effects on NH3 -SCR activity on Fe2 O3 -NR and Fe2 O3 -NS, respectively; despite this, Fe2 O3 -NR showed higher affinity for SO2 + O2 . This work set a milestone in understanding the NH3 -SCR reaction on Fe2 O3 catalysts in the presence of SO2 from the aspect of crystal facet engineering.