N-doped graphene/CoFe2O4 catalysts for the selective catalytic reduction of NOx by NH3

Abstract

In this paper, CoFe₂O₄/graphene catalysts and N-doped graphene/CoFe₂O₄ (CoFe₂O₄/graphene-_N) catalysts were prepared using the hydrothermal crystallization method for the selective catalytic reduction of NO_x by NH₃. The results of the test showed that CoFe₂O₄/graphene catalysts exhibited the best denitrification activity when the loading was at 4% and the conversion rate of NO_x reached 99% at 250–300 °C. CoFe₂O₄/graphene-_N catalysts presented a better denitrification activity at low temperature than CoFe₂O₄/graphene catalysts, and the conversion rate of NO_x reached more than 95% at 200–300 °C. The intrinsic mechanism of CoFe₂O₄/graphene-_N catalysts in promoting SCR activity was preliminarily explored. The physicochemical properties of the samples were characterized using XRD, TEM, N₂ adsorption, XPS, NH₃-TPD, and H₂-TPR. The results indicated that nitrogen doping can improve the dispersion of CoFe₂O₄, and it also increased the acidic sites and the redox performance conducive to improving the denitrification activity of the catalysts. In addition, CoFe₂O₄/graphene-_N catalysts demonstrated a better resistance to water and sulfur than CoFe₂O₄/graphene catalysts.