Low-temperature selective catalytic reduction of NO with NH3 over nanoflaky MnOx on carbon nanotubesin situ prepared via a chemical bath deposition route

Abstract

Nanoflaky MnO_x on carbon nanotubes (nf-MnO_x@CNTs) was in situ synthesized by a facile chemical bath deposition route for low-temperature selective catalytic reduction (SCR) of NO with NH₃. This catalyst was mainly characterized by the techniques of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), N₂ adsorption–desorption analysis, X-ray photoelectron spectroscopy (XPS), H₂ temperature-programmed reduction (H₂-TPR) and NH₃ temperature-programmed desorption (NH₃-TPD). The SEM, TEM, XRD results and N₂ adsorption–desorption analysis indicated that the CNTs were surrounded by nanoflaky MnO_x and the obtained catalyst exhibited a large surface area as well. Compared with the MnO_x/CNT and MnO_x/TiO₂ catalysts prepared by an impregnation method, the nf-MnO_x@CNTs presented better NH₃-SCR activity at low temperature and a more extensive operating temperature window. The XPS results showed that a higher atomic concentration of Mn⁴⁺ and more chemisorbed oxygen species existed on the surface of CNTs for nf-MnO_x@CNTs. The H₂-TPR and NH₃-TPD results demonstrated that the nf-MnO_x@CNTs possessed stronger reducing ability, more acid sites and stronger acid strength than the other two catalysts. Based on the above mentioned favourable properties, the nf-MnO_x@CNT catalyst has an excellent performance in the low-temperature SCR of NO to N₂ with NH₃. In addition, the nf-MnO_x@CNT catalyst also presented favourable stability and H₂O resistance.