Anatase TiO₂-supported manganese and cobalt oxide catalysts with different Co/Mn molar ratios were synthesized by a conventional impregnation method and used for selective catalytic reduction (SCR) of NO_x with NH₃. The catalysts were characterized by N₂ adsorption/desorption, X-ray diffraction, X-ray photoelectron spectroscopy, and temperature-programmed desorption with NH₃ and NO_x. Characterization of the catalyst confirmed that by using Co₃O₄ over Mn/TiO₂, we enhanced NO oxidation ability. From in situ diffuse reflectance infrared transform spectroscopy (DRIFTs) analysis of desorption and the transient reaction, we concluded that the addition of Co could remarkably lower the activation energy of NO_x chemisorption on the catalyst surface. In addition, low-temperature SCR activity mainly results from a “fast SCR” reaction. We observed four NO_x species (bidentate nitrates, gaseous NO₂, linear nitrites, and monodentate nitrites) on the surface of Mn/TiO₂ and Co–Mn/TiO₂ catalysts that all participated in the SCR reaction in the high temperature range. Doping of cobalt greatly improved the reactivity of gaseous NO₂, linear nitrites, and monodentate nitrites, which makes Co–Mn/TiO₂ a highly effective NH₃–SCR catalyst.

The MnO_x and CeO_x were in situ supported on carbon nanotubes (CNTs) by a poly(sodium 4-styrenesulfonate) assisted reflux route for the low-temperature selective catalytic reduction (SCR) of NO with NH₃ . X-Ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray photoelectron spectroscopy (XPS), H₂ temperature-programmed reduction (H₂-TPR) and NH₃ temperature-programmed desorption (NH₃-TPD) have been used to elucidate the structure and surface properties of the obtained catalysts. It was found that the in situ prepared catalyst exhibited the highest activity and the most extensive operating-temperature window, compared to the catalysts prepared by impregnation or mechanically mixed methods. The XRD and TEM results indicated that the manganese oxide and cerium oxide species had a good dispersion on the CNT surface. The XPS results demonstrated that the higher atomic concentration of Mn existed on the surface of CNTs and the more chemisorbed oxygen species exist. The H₂-TPR results suggested that there was a strong interaction between the manganese oxide and cerium oxide on the surface of CNTs. The NH₃-TPD results demonstrated that the catalysts presented a larger acid amount and stronger acid strength. In addition, the obtained catalysts exhibited much higher SO₂-tolerance and improved the water-resistance as compared to that prepared by impregnation or mechanically mixed methods.