Activating well-defined ?-Fe2O3 nanocatalysts by near-surface Mn atom functionality for auto-exhaust soot purification

Herein, the atomically dispersed manganese (Mn) sites on well-defined alpha-Fe2O3 nanosheets (Mn1-Fe2O3) were fabricated by a ligand-assisted in-situ crystallization method. Single-step surface engineering facilitates the in-situ replacement of Fe atoms in near-surface [FeO6] octahedra with monodispersed Mn atoms, as well as the preservation of regularly exposed {001} surface. Under different NOx concentration (40, 500 and 2000 ppm), Mn1Fe2O3-10 catalyst presented the superior catalytic performance, whose T50 values are 455, 388 and 340 degrees C, respectively. By combining in-situ dynamic characterizations and DFT calculations, the surface [MnO5] and adjacent [FeO5] octahedra cooperatively boost two crucial steps: the dissociation of adsorbed O2 and the desorption of molecular NO2. The greater the amount of molecular NO2 produced, the higher the efficiency of soot purification via the NO2-assisted oxidation mechanism. Insights into the near-surface modulation and structure-activity relationship provide a promising strategy to improve the availability of surface-active sites in future heterogeneous catalysis.