Investigation of the structure, acidity, and catalytic performance of CuO/Ti0.95Ce0.05O2 catalyst for the selective catalytic reduction of NO by NH3 at low temperature

• Ce4+ has been successfully incorporated into the lattice of anatase TiO2 to form uniform Ti0.95Ce0.05O2 solid solution.
• The coordination status of Cu2+ in CuO/Ti0.95Ce0.05O2 catalyst is an unstable distorted octahedral coordination structure.
• The redox cycles of Cu2+ + Ce3+ ↔ Cu+ + Ce4+ and Cu2+ + Ti3+ ↔ Cu+ + Ti4+ may be established in CuO/Ti0.95Ce0.05O2 catalyst.
• Lewis acid site plays an important role in NO + NH3 + O2 model reaction.

Anatase TiO2, Ti0.95Ce0.05O2 solid solution, and CeO2 were synthesized by inverse co-precipitation method, and then used as supports to prepare CuO/TiO2, CuO/Ti0.95Ce0.05O2, and CuO/CeO2 catalysts through incipient-wetness impregnation method. The obtained samples were investigated in detail by means of N2-physisorption, XRD, LRS, H2-TPR, XPS, NH3-TPD, and in situ DRIFTS technologies. Furthermore, NH3-SCR of NO in the presence of excess oxygen was chosen as a model reaction to evaluate the catalytic performances of these samples. The obtained results indicate that the incorporation of Ce4+ into the lattice of anatase TiO2 leads to the formation of unstable distorted octahedral coordination structure of Cu2+ in CuO/Ti0.95Ce0.05O2 catalyst and the enhancement of the electron interaction between copper oxide species and Ti0.95Ce0.05O2 support through the redox cycles of Cu2+ + Ce3+ ↔ Cu+ + Ce4+ and Cu2+ + Ti3+ ↔ Cu+ + Ti4+, which are beneficial to the formation of more Lewis acid sites on the surface of CuO/Ti0.95Ce0.05O2 catalyst and the activation of reactant molecules to generate more NH4NO2 species, all of these may promote the enhancement of catalytic performance for NH3-SCR of NO in the presence of excess oxygen. Finally, a possible reaction mechanism (schematic diagram) is tentatively proposed to further understand this model reaction.

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