Low-temperature NH₃-SCR has attracted considerable attention owing to the vast demand in industrial furnaces and its energy-conserving feature. This review summarizes the recent advances in the application of ceria-based catalysts for low-temperature NH₃-SCR.

NO removal by CO model reaction was investigated over a series of ceria-containing solid solutions, prepared by an inverse co-precipitation method, to explore the relationship between the physicochemical properties and catalytic performances of these catalysts. The synthesized samples were studied in detail by means of XRD, Raman, TEM, UV-Vis spectroscopy, N₂-physisorption, H₂-TPR, OSC, XPS and in situ FT-IR technologies. These results indicate that the incorporation of Zr⁴⁺, Ti⁴⁺ and Sn⁴⁺ into the lattice of CeO₂ leads to a smaller grain size and enhanced reduction behavior. Furthermore, the catalytic performance test shows that the activities and selectivities of these solid solutions are higher than pure CeO₂ and that the Sn⁴⁺-doped sample shows the best results. The reason may be that: (1) the decrease in grain size results in an enlargement of the BET specific surface area and an increase of surface Ce³⁺. The former is conducive for sufficient contact between the catalyst and reactant molecules and the latter contributes to the adsorption of CO_x species; (2) the enhanced reduction behavior is beneficial in generating more surface oxygen vacancies during the reaction process, which can weaken the N–O bond to promote the dissociation of NO_x effectively. Finally, in order to further understand the nature of the catalytic performances for these samples, a possible reaction mechanism is tentatively proposed.

This work is mainly focused on investigating the influence of preparation methods on the physicochemical and catalytic properties of CuO–CeO₂ catalysts for NO reduction by CO model reaction. Five different preparation methods have been used to synthesize CuO–CeO₂ catalysts: mechanical mixing method (MMM), impregnation method (IM), grinding method (GM), hydrothermal treatment method (HTM) and co-precipitation method (CPM). All of these samples were characterized by a series of techniques such as N₂-physisorption, XRD, LRS, H₂-TPR, ICP-AES, XPS, in situ FT-IR and NO + CO model reaction. The obtained results show that the catalytic performances of these CuO–CeO₂ catalysts can be ranked by CuCe-IM > CuCe-CPM > CuCe-GM > CuCe-HTM > CuCe-MMM, which is in agreement with the orders of the surface oxygen vacancy concentration, reducibility and Cu⁺ content, suggesting that the synergistic effect between Cu⁺ species and surface oxygen vacancies of these CuO–CeO₂ catalysts plays an important role in this model reaction. In order to further understand the synergistic effect, a possible reaction model is tentatively proposed.