In Situ DRIFTs Investigation of the Low-Temperature Reaction Mechanism over Mn-Doped Co3O4 for the Selective Catalytic Reduction of NOx with NH3

The Co3O4 and Mn-doped Co3O4 nanoparticle were synthesized by a co-precipitation method and used as selective catalytic reduction of NO with NH3 (NH3-SCR) catalysts. After the doping of manganese oxides, the NH3-SCR activity of Mn0.05Co0.95Ox catalyst is greatly enhanced. The NO oxidation ability of two catalysts is compared, and the X-ray diffraction results demonstrate that Mn has been successfully doped into the lattice of Co3O4. The X-ray photoelectron spectroscopy and temperature-programmed reduction with H2 results confirmed that there is a strong interaction between Mn and Co in the Mn0.05Co0.95Ox catalyst. Their adsorption and desorption properties were characterized by temperature-programmed desorption with NH3 or NO + O2 and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTs). These results indicated that the doping of manganese could provide more acid sites on the catalysts, and bidentate nitrates species originated from NOx adsorption are obviously activated on the Mn0.05Co0.95Ox catalyst surface. Moreover, the transient reaction studied by in situ DRIFTs found that the “fast SCR” reaction participated by gaseous NO2 and the standard SCR reaction participated by bidentate nitrates contribute to the low-temperature SCR activity.