The promoting effect of noble metal (Rh, Ru, Pt, Pd) doping on the performances of MnOx–CeO2/graphene catalysts for the selective catalytic reduction of NO with NH3 at low temperatures

Abstract

Noble metal (Rh, Ru, Pt, Pd) doped MnOx–CeO₂/graphene catalysts were prepared by a hydrothermal method, which exhibited promoting effects on the selective catalytic reduction (SCR) of NO with NH₃ at low temperatures. The catalytic activity test results suggested that MnOx–CeO₂–Pd/GR exhibited the best catalytic performance. Moreover, the addition of Pd to MnOx–CeO₂/GR enhanced the resistance to SO₂ poisoning. The obtained samples were characterized by XRD, HR-TEM, Raman, BET, XPS, H₂-TPR and NH₃-TPD. The results indicated that the doping of Rh, Ru, Pt or Pd had a synergistic effect due to the interaction between the dopant and the MnOx–CeO_x solid solution. These interactions could improve the catalytic activity at low temperatures, because of the larger specific surface area and the higher atomic content of Mn⁴⁺ on the catalyst surface. Furthermore, Rh, Ru, Pt or Pd doping increased the amount of the chemisorbed oxygen and the surface acid sites, which played important roles in the SCR reaction process.