Studying the structure-reactivity relationship of CuO/CeO2 for catalytic soot particulate combustion: on the monolayer dispersion threshold effect

To elucidate structure-reactivity relationship and prepare improved catalysts for soot combustion, a series of CuO/CeO2 with different loadings have been fabricated by the impregnation method. With XRD and XPS extrapolation methods, it is disclosed that CuO disperses finely on the CeO2 support to form a monolayer with a capacity around 1.06 mmol 100 m(-2), which equals to 2.9 wt. % CuO loading. Below this capacity, CuO is in a sub-monolayer state. However, above this capacity, CuO micro-crystallites are formed, and co-exist with the monolayer CuO. By increasing CuO loading, soot combustion activity of the catalysts increases as well until it reaches the monolayer dispersion capacity. Further increasing the CuO loading to 5 % decreases the activity slightly, and then remains constant. Therefore, an apparent monolayer dispersion threshold effect is observed for soot combustion on CuO/CeO2 catalysts. It is found that the amount of surface-active O-2- sites plays critical role for the catalytic activity. To obtain the most active CuO/CeO2 catalyst, a monolayer amount of CuO should be loaded on the supports.