Structure sensitivity of CuO in CO oxidation over CeO2-CuO/Cu2O catalysts

Several CeO2-CuO/Cu2O nanocomposites with different CuO structures were used to identify the structure sensitivity of CuO in the CeO2-CuO/Cu2O catalyzed CO oxidation. The CO oxidation catalyzed by various CuO-CeO2 interfacial sites involves a typical Mars-van Krevelen mechanism, in which the CuO-CeO2 interfaces in the CeO2-CuO/c-Cu2O (cubes) nanocomposites are more intrinsically active, exhibiting ca. 15 kJ mol−1 lower activation energy than those in the CeO2-CuO/o-Cu2O (octahedra) and CeO2-CuO/d-Cu2O (rhombic dodecahedra) nanocomposites at CeO2 loadings no less than 0.75 wt%. The higher activity is relevant to lower coordinated oxygen ions on CuO/c-Cu2O surface and thus better CO reactivity for the CeO2-CuO/c-Cu2O nanocomposites, which therefore indicates that the active oxygen species on CuO-CeO2 interface should come from CuO rather than CeO2. Moreover, a highly active 13.2 %CeO2-CuO/c-Cu2O(s) catalyst for CO oxidation is realized on fine Cu2O cubes, which thus has high density of active sites.