Novel Mn-Cu-Containing CeO2 Nanopolyhedra for the Oxidation of CO and Diesel Soot: Effect of Dopants on the Nanostructure and Catalytic Activity

Ceria-based catalysts doped with manganese and copper were obtained via the hydrothermal synthesis. Four systems were synthesized: CeO2 (pure ceria), Ce0.95Mn0.05 (Mn/Ce at. ratio = 1/19), Ce0.95Cu0.05 (Cu/Ce at. ratio = 1/19) and Ce0.95Mn0.025Cu0.025 (Mn/Cu/Ce at. ratio = 1/1/38). The catalytic activity of the prepared materials was tested for the CO and soot oxidations. Complementary techniques (XRD, N-2 physisorption at - 196 degrees C, FESEM, XPS, Raman spectroscopy, CO-TPR and Soot-TPR) were performed to investigate their physico-chemical properties. The samples were characterized by nanocubes, in the case of CeO2, and by nanopolyhedra for binary (Ce0.95Mn0.05 and Ce0.95Cu0.05) and ternary oxides (Ce0.95Mn0.025Cu0.025). The CO-TPR analysis has confirmed that the reducibility follows the order: CeO2 < Ce0.95Mn0.05 < Ce0.95Mn0.025Cu0.025 < Ce0.95Cu0.05. A similar trend appears for the surface defective sites (Raman spectroscopy). These findings suggest the beneficial role of dopants in improving the structural defects and the surface reducibility of ceria. Both properties promote the CO oxidation activity. In fact, the Ce0.95Cu0.05 was the most effective catalyst for the CO oxidation. The Ce0.95Mn0.05 sample exhibited the best performance in soot oxidation. The following order was achieved: Ce0.95Mn0.025Cu0.025 < Ce0.95Cu0.05 < CeO2 approximate to Ce0.95Mn0.05, in agreement with the reduction profiles obtained by the Soot-TPR above 400 degrees C.