Enhanced low-temperature behavior of selective catalytic reduction of NOx by CO on Fe-based catalyst with looping oxygen vacancy

The industrial applications of de-NOx require the high activity window of the catalysts to be shifted from high to low temperatures for energy saving. Selective catalytic reduction (SCR) of NOx by CO, as an alternative to NH₃-SCR, is a promising de-NOx technology that facilitates the synergistic removal of pollutants. Herein, we report a new Fe₂O₃/amorphous SiO₂ catalyst with high low-temperature activity for CO-SCR. A combination of experiments and density functional theory (DFT) calculations obtains direct evidence that an optimal content of oxygen vacancy enhances the low-temperature NO conversion ratio and N₂ selectivity of Fe₂O₃-based catalyst to over 80% and maintain 100% CO conversion by promoting NN coupling via ONNO/N₂O and NCO/NNCO₂ intermediates. Compared with conventional defect engineering, such as doping other metals or artificially generating oxygen defects, the α-Fe₂O₃ (1 1 0) facet automatically enables an oxygen vacancy generation-filling cycle in the CO-SCR reaction, following Mars-van Krevelen (MvK) mechanism. This work advances a fundamental understanding of CO-SCR reaction mechanism over Fe₂O₃-based catalysts and provides insights for future studies to improve heterogeneous metal oxide catalysts.