Morphology and crystal–plane dependence of CeO2–TiO2 catalysts: Activity and mechanism for the selective catalytic reduction of NOx with NH3

CeO 2 –TiO 2 catalysts with four different morphologies were successfully synthesized by a hydrothermal method and tested for selective catalytic reduction of NO x with NH 3 (NH 3 –SCR). For the four catalysts, CeO 2 –TiO 2 nanocubes (CT–NC) and nanorods (CT–NR) preferentially exposed {1   0   0} and {1   1   0} facets, respectively; furthermore, nanosheets (CT–NS) and nanospheres (CT–NH) mainly exposed {1   1   1} facet. Interestingly, CT–NH catalyst showed the best NH 3 –SCR performance and the NO x conversion exceeded 97% at 325 °C. Through a series of characteristic methods manifested that the short–range ordered structure of Ce–O–Ti in CT–NH catalyst provided stronger surface acidic sites to promote the high–temperature activity. Moreover, the abundant Ce 3+ species and appropriate reduction ability on {1   1   1} facet of CT–NH catalyst also caused outstanding de NO x activity. Reaction mechanism study showed that the Langmuir–Hinshelwood (L–H) mechanism and Eley–Rideal (E–R) mechanism existed simultaneously on all catalysts in NH 3 –SCR reaction. Meaningfully, two types of E–R mechanism were present on CT–NH catalyst, while L–H mechanism was dominant.