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

The Co 3 O 4 and Mn-doped Co 3 O 4 nanoparticle were synthesized by a co-precipitation method and used as selective catalytic reduction of NO with NH 3 (NH 3 -SCR) catalysts. After the doping of manganese oxides, the NH 3 -SCR activity of Mn 0.05 Co 0.95 O x 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 Co 3 O 4 . The X-ray photoelectron spectroscopy and temperature-programmed reduction with H 2 results confirmed that there is a strong interaction between Mn and Co in the Mn 0.05 Co 0.95 O x catalyst. Their adsorption and desorption properties were characterized by temperature-programmed desorption with NH 3 or NO + O 2 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 NO x adsorption are obviously activated on the Mn 0.05 Co 0.95 O x catalyst surface. Moreover, the transient reaction studied by in situ DRIFTs found that the “fast SCR” reaction participated by gaseous NO 2 and the standard SCR reaction participated by bidentate nitrates contribute to the low-temperature SCR activity.